I enjoy working on my own car, solving each mystery, addressing each issue & have accumulated a good deal of knowledge, so I am hooked but am interested to hear some opinions on how much more I should do considering the age of/wear on the car. Only paid $1K, 215K ... just seems to be having a midlife crisis, suffering from weather & oil abuse, hoping to get at least another 5-10 years.

Also curious as to an estimate of pure labor costs I have saved doing the work myself ... here's what I've done so far (and I have alot of pics but not sure where/how to post them, in my Garage Album?) ...

Replaced Battery & Starter (due to no start)
Replaced End Muffler (due to rust)
Replaced O-Ring on Camshaft Position Sensor (due to oil leak)
All new Spark Plugs (due to age)

Top-End Cleaning & New Gaskets (due to carbon/varnish buildup & oil seepage): UIM (EGR & TB Ports), IACV (re-used old gasket), Throttle Body (re-used old gasket), EGR Tube (re-used old gaskets), Valve Covers, Tube Seals, Grommets, MAF (original, cleaned), New Air Filter
Oil & Filter Change #1
New PCV

Homemade fix for rusted out Radiator Core Support (due to age/weather) ... thanks to the boyfriend

New Alternator (due to oil damage)
New PS Belt (due to original belt worn)
Removed, Cleaned, Restored all Original Tensioners: PS Pulley, Idler Pulley & Timing Chain
Removed, Cleaned & Re-sealed Outer Timing Chain Cover (due to oil leak, chain/guide inspection + education): New RTV, Crankshaft Seal & Front Upper Oil Pan Seal, TC & Water Pump Access Covers Cleaned & Re-Sealed
New Water Pump
New Thermostat

Also enjoyed my 1st Junkyard venture:
Driver's Door Switch (in attempt to rid the common blinking airbag light - still on my to-do list)
Camshaft Position Sensor (noticed a few hairline cracks developing when I cleaned the original)
Much-Less-Rusty-Than-Mine Horn & Bracket

Oil & Filter Change #2 (#1 was already mud after only 2 weeks + we whacked the filter with the breaker bar getting the crankshaft bolt loose)

Cleaned Oil Strainer & Lower Oil Pan & Re-sealed
Cleaned the **** out of the Crankshaft Position Sensor & Oil Pressure Switch Inlet (covered in sludge, used MAF cleaner)
Replaced Oil Pressure Switch

Replaced Bank 1 Front O2 Sensor - more help here from my favorite "nut buster" - a rough one (due to CEL Codes I had pulled back when I purchased the car in 2014 ... P1148, P0300 & P0130 all pointed to it)

Pulled out ECU to check for obvious damage before suspecting IACV for rough, erratic idle under load, looked good. Tried to pull codes from ECU with screw, but nothing at all ... that's when I realized the CEL bulb was burned out, so replaced it, works fine now.

I've researched the idle problem ALOT ... just got the CEL for 1st time since all this work (otherwise, everything started right up, completely better after the chain tensioner re-pressurized lol & runs great btw) ... got a beautiful P0305 (sent by the un-gunked CKPS I assume), replaced the Coil Pack #5 & the idle problem was gone!

I took care of alot of good things but now realize I was so close anyway, I probably should have tackled the RMS & those two pesky O-Rings behind the Inner TC Cover, as I am 90% sure that is where my tiny oil leak (about a poker chip size spot overnight) is still coming from (even though I eliminated several others) - I get the gravel space in the driveway for now lol.

My To-Do's:
Guessing new Catalyst - hearing a putt-putt and assume the coil pack issue has probably worn on it & it's surely the original - hoping rest of exhaust & Y-pipe aren't too rusty... waiting for more codes/clues (checking tomorrow: CEL is on after replacing the #5 Coil Pack & I expect more)
Replace Tranny Pan Seal & Coolant Hoses (seeping, not dripping)
New Shocks/Struts
New Windshield (will prob pay to have that done)
Probably PS Pump & Hoses (still original, some seepage)
Tires, maybe Rims, within next couple of years
MAYBE RMS & Rear TC Cover O-Rings

So ... I'm still under $600 for what I've spent on parts ... I love the engine & feel, so is there anything else I should check or stop at that is a popular deal-breaker for this car? I don't think I'd get into wiring or the trans, but is this all worth it? These cars seem to be able to run very high mileage lifetimes, but wondering if I caught this one too late...

Thanks in advance for any advice or input ... I will post the pics tomorrow & update on any new codes/progress!"

I got the Century Writer Award right off the bat for that one lol ... photos are now in my SPRING CLEANING Album (in order) ... anything I missed or obviously bad from the photos? Thanks again to CS AR for the feedback on the noobie thread

Hey Jen - Welcome to the 4th gen 99 model club.

Here's a tip from a dual 99 model owner.

Keep a spare Transponder Chip Key

Since your Maxima uses a "transponder chip key" keep a spare key around in the even the chip fails. Attempting to start a 99 Model or later Maxima with a failed transponder chip key can result in the Nissan Anti-Theft System (NATS) immobilizing the car.

Getting the NATS immobilizer reset is not cheap. Sometimes it requires the car being towed to the dealer for a NATS reset. Many hardware stores can now duplicate transponder chip keys for less than $80. Keeping a spare transponder key handy is good insurance for avoiding tow charges and/or expensive service charges.

There is a link in my signature line about NATS and immobilization. It is good to be aware of the information provided in that link.

Thanks again - I actually have the original spare key - I'll make sure it has the chip & works, and then I should be all set there - great advice -assuming its a keeper then 🙌

UPDATE: Same/similar running condition after Cylinder #5 Misfire Code & replacing Coil Pack #5 Does not like idling in gear (i.e. waiting at stoplight), worse as engine warms up, some remaining hesitations when picking up speed, then fine once driving in higher gears (A/T). I've read ALOT on this idle issue but there are SO many possibilities. Just pulled 0304 & 0701 blinks from ECU screw, so dismissing the KS for now, but investigating the Multiple Misfire per the FSM ...

No apparent intake leaks, no obvious physical damage to exhaust/cat other than rust.

FSM says check EGR system next ... when I had the UIM off, I thoroughly cleaned the EGR Tube (was completely packed solid), tried my best to clean up the sludge right inside the UIM at the EGR Port, and removed the EGR Temp Sensor for a good cleaning as it was sludged too, re-used original gaskets ... At this point (tell me if I'm wrong), I assume that since I am not getting any EGR codes, the system is operational. I remember seeing something in my extensive research about cleaning sticky EGR Valves, but wouldn't I get a code for that being the issue?

Next per the FSM is the Power Balance Test so after lunch, I am preparing to start her up & pull each coil pack connector one at a time to see how it affects things ... will update again soon...

Jen - Are you noticing any differences with the #5 plugin terms of blackening or fuel smell?

The reason I'm asking is we are seeing some number of injector leaks that cause misfires due to flooding.

I remember having injector pintle cap/o-ring failure on cylinders #2 and #5 that caused serious flooding and misfires.

Two other members have experienced broken pintle caps / leaking o-rings -- possibly on #5.

Threads of interest below.

https://maxima.org/forums/4th-genera...ng-up-gas.html

https://maxima.org/forums/4th-genera...ite-smoke.html

..

^ Thanks for the nudge in a GREAT direction CS_AR! Didn't notice any blackening on #5 but didn't inspect the spark plug ... Old coil pack didn't look that bad physically, not a strong enough fuel smell to startle me, but ...

Read both threads you suggested & I'm diving in...

No SC setup like Wizard lol, but ALOT of similarities ... no billowing white smoke or backfire, no cranking issue (just put new starter, batt & alt in), just wispy white smoke & the putt-putt, guessing I might be in an earlier stage? Was already doubting the health of the cat, so after reading his experience, I'm almost 100% mine is already toast due to this issue, or will be soon ... no emissions test due til Sept, so I have a little time.

Got the 3 codes that all pointed to the Left Front O2 Sensor last year when I got the car, so just replaced it ... really don't want to fry it so I'm gonna do the right thing ... the UIM is coming back off.

I don't think I'll have the injectors serviced, I just didn't realize this issue and that they were RIGHT THERE, when I had everything apart the first time around ... live & learn! At least it will be alot easier having already done it once

I'm ordering the full O-Ring sets from rockauto with the top insulators because I do have alot of corrosion (plus I'll replace the FPR while I'm in there). Assuming I most likely have pintle issues as well.

Spark Plugs are brand new ... I'll of course check the injectors for function & be sure to update with photos & details of what I find once I get in there. Said it once & I'll say it again ... this site is amazing ...thanks!

Pintle caps, o-rings, and screens if you can get them.

If you open the injectors and replace the FPR, you'll want to replace easy to strip brass Phillips head screws with stainless socket head cap screws. I pick up Hillman Stainless Fasteners from hardware stores like Lowe's or Ace Hardware.

Injector Caps and the Fuel Pressure Regulator use M5 (size) 0.8 (pitch) x 16mm (length) with M5 lock washers.

If you have a good shop that can clean and service your injectors it is a lot less work. Though, I used this kit to refurbish mine last year.

http://www.ebay.com/itm/Fuel-Injecto...-/201023508532

This thread might be of interest also. Approach not required but possibly some interesting reading..

https://maxima.org/forums/4th-genera...k-testing.html
'
:

Just realized the need for pintles showing the bf those pics of the broken ones last night - I had just found a set on ebay exactly like the set you linked to when I checked back here & saw your reply lol - your set was a few bux cheaper, cool.

Keeping costs low are key for me & the best deal I could find on a FPR was rockauto for about $50+S/H, so decided I'm gonna primarily stick to the pintle/0-ring injector refurb project but I will check the vac line on the FPR for gas and go from there. Also read about the pump o-ring failing so I'll see what that situation looks like too. After reading symptoms & how to test fuel pump & FPR, I feel they may be ok anyhow as I have zero cranking issues.

The only question I have is about the ebay refurb kit - no insulators. How risky is re-using the originals?

Otherwise, wish me luck & I'll be back in touch soon...

I reused insulators but they were from an engine with less miles. If yours do not look good then I would just replace them.

Sent from my Z998 using Maxima

It's been almost a year of sharing a different vehicle with my man ... thanks to the tax return, the PITA of sharing a vehicle is almost over ... parked the car the entire time since my last post until now ... just got the parts to proceed with the next step, but now I need some more help/guidance from you wonderful people...

Thought it would be easier to bump the original thread for anyone that wanted to learn the back story without me having to repeat myself (LOTS of details) ... sorry if it's a "no-no" ...

SO ... As suggested, because I was still getting multiple misfire codes (& ignoring the KS code for now),already replaced coil pack #5 due to earlier specific code & 99's are known for coil packs going out (220K now, were all original) ... I bought another 5 coil packs to replace the 5 remaining originals. Spark Plugs were still new from earlier work last year.

I also got the suggested Ebay fuel injector kit to refurbish the originals - came with screens, both o-rings & pintle caps. I did not remove the fuel rail - I very carefully with strong, steady twisting pressure, pulled them out of the installed fuel rail one by one. Upon inspection, very gritty & dark screens, o-rings didn't seem too brittle but the grooves they sat in were sludgy, and all the pintle caps were there but some had the little teeth broken off. Screens & o-rings came off easily & the new ones were simple to install (I did coat the new o-rings with a tiny amount of clean motor oil).

This is the point where I might have caused a problem - I don't know how picky/delicate injectors are, I tried being as gentle as possible, but I had some pintle cap issues - the old ones were brittle but so tight I had to carefully cut them off at an angle with the tip of a pair of wire cutters - I only VERY slightly nicked a couple of the pintles on the SIDE, not bottom, in doing this. Then I thought that would be the worst of it but it was even more difficult to get the new ones ON - I used a tiny rubber mallet to lightly tap them (afraid to hit them too hard) but I still had to work them on to get up over the groove with pliers, again, as gently as possible, but I did get them on - wondering if they are supposed to spin in the groove when on or should they not move at all? The edges are a little mangled from being gripped with the pliers and I did break one tooth off one of them. At the time, I debated even putting them on because I read some posts here on the org about people leaving them off & having no issues - I went ahead tho, figuring there were many more broken teeth before the process so only one missing on the new caps wouldn't be any worse than before. That's what I get for trying to think at 2am

Next, I got to eat a little humble pie ... On first startup trial, cranked fine, but no start ... expected since I had the injectors out & fuel line depressurized, but still no start after several attempts ... heard evidence of fuel pump working & re-pressurizing when turning key to ON position, but no start. Worst feeling after all the work I did BUT I kept calm & jumped into more research - quickly realized I needed to re-check all the connections, hoses, plugs, clamps, etc. that I removed & replaced to do the job. The first time I took the UIM off last year, I was so new & careful, I labeled everything as I did the disassembly to make sure I put it all back together correctly. This time, I got cocky, having done it before, and did not. Turns out there were 3 things I missed: I left off the small hose that attaches to an inlet a little left of top dead center on the UIM ... the electrical connector on the left end of the rear bank (not sure what for, bf guessed something to do with fuel delivery), was plugged in but not CLICKED fully into socket ... worst of all, when I replaced the fuel pump fuse inside the dash panel, it was supposed to go back in its slot #32, but I saw the only other empty slot a couple down the column and put it there by mistake (#34 I think, which is normally empty). Still thought I hadn't done too bad considering I hadn't labeled anything, BUT we made all those start-up tries with those three problems, which I am hoping did not cause any damage.

Once those 3 things were corrected, it still would not start tho, so I went back to more research ... thought maybe spark plugs got wet, so we pulled #3, being the easiest to access, and it was dry, no gas smell. No gas smell around fuel rail & injectors. When I installed the injectors, again going for the gentler approach (saw pros and cons for both hammer-tap and retainer cap method), I just set them in evenly, no pushing, and as I installed the retainer caps, I went back & forth between the two screws, which gently pressed the injector into place as the cap went down ... they all look seated properly, level with surface of orifice & even, same as they looked before. After visually checking the one spark plug & injector seating, we tried again and this time it started on about the 3rd or 4th attempt!

So I took it for the celebratory drive around the block to test things out. The rotors were grinding a little from sitting so long, but that's not a major problem. We heard a NEW strange whacking noise & the engine was running rougher when I pulled in to park so I shut the car off right away ... to my surprise, when I turned it off and took out the key, the engine kept running, but was chugging & choking itself out, dieseling I've learned ... I panicked & could only think to hit the brake pedal (A/T), which actually did stop it completely, only lasted a few seconds that seemed forever, but sounded like it was about to stop itself anyhow. I had to run a quick errand (in the other vehicle), and when I got back, decided to pull my car back in the garage to take a look at things & do more research for this new symptom, it started up fine, ran rough, speedy idle, but again the dieseling when I shut it off.

This time my discovery was either due to storage or my appetite for more humble pie ... either way, lucky because we did some serious highway test driving before I parked it for the year due to the misfire codes ... the idler pulley (pretty rusty already since cleaning it up last year) was loose and the belt was still on, but had jumped over a groove on the alternator. No damage to belt, glad I stopped it as quickly as I did.

I remembered something important about the order to loosen the pulley vs tensioner bolts but the bf wanted to jump in and just fix it (he is very experienced so sometimes it's hard for him to stand by & watch me "learn" ) ...I made him wait while I checked the org and sure enough he had been cranking on the tensioner bolt when he needed to pop the pulley bolt loose first. Once I explained, it was off to the races and he just finished it ... belt looked good so put it back on, adjusted the tension & tightened the idler pulley back on ... I cringed a little & I know he was just worried about it not vibrating loose, but he shook the whole car tightening that pulley bolt, cranked it on HARD ... just smiled thanks and keeping my fingers crossed there are no evil consequences from overtightening that particular bolt.

Pulley & belt fixed, I crossed my fingers & started it up, belt & pulley looked ok according to bf, but still running rough, idle changes (but not bouncing), and again, the diesling. After the work I did, the numerous, various start-up attempts under many different conditions, my final thought of the evening was the poor ECU was getting alot of crazy feedback & maybe trying to make all kinds of crazy adjustments, so I unhooked the battery & went to bed ... that was the end of last night.

Had things to do today but did some more research & here's where I'm at now ... my most telling symptom is the dieseling, I think due to crappy gas, idle adjusted too high, running too hot, or last but not least, problem with fuel injectors. The 1/3 tank of gas in it has been sitting since last year when I last worked on it, but that's something I was about to & need to take care of right away anyway, out with the old, in with some nice, high octane new. The idle wasn't right before either ... the bf jumped in last year trying to adjust it & I believe we tried doing it with the throttle cables and the IACV screw to account for the low points of the "rough idle in gear while brake on" issue. The thermostat, water pump & coolant are all new & car doesn't seem to run hot but there is alot of carbon build up still from the previous owner. The last check would be to get the injectors back out to check/change the pintle caps and/or replace injectors - I understand they could have interior problems/clogging that my rebuild did not address.

At this point, I don't want to cause any damage by starting the car if it is going to continue the dieseling. My first plan is to get a code reading off the ECU screw, but I believe I would have to start the car to get it to throw a code since the battery has been disconnected. Sorry for the long read, but looking for any direction/advice I can get before I do anything else & I know details can be important ... what is the best way to proceed? Thanks in advance ...

As I recall, the new pintle caps fit tight, very tight.

To install the new pintle caps, I matched up a barrel socket that was the same size as the cap. I just placed the cap into the socket then pressed the injector into the cap. The socket was the guide. So with the socket on my workbench, I just held the injector in my hand and leaned into it forcing the tip into the pintle cap. Then I adjusted the cap position so the little tips looked like the ones on a good injector.

Since you have a 99 model with NATS, be careful to keep the drivers door closed if you are running the starter for diagnostics. It is easy to accidentally trip the NATS immobilizer which can require a trip to the dealer for a reset.

Thanks CS... glad to see you're still around ...
And thanks for the reminder about the NATS ...

I have some pics of the injectors & pintle caps before & after I'll get off my phone & put on here a little later ...

I do tend to get wordy lol, so here are the specific questions I still have:

Is it possible I confused the hell out of (or damaged) the ECU with all the different condition start trials I put it through?

(Maybe wait till I get my photos up, but...) Did I screw up the new pintle caps? They were in no way loose or spinning once installed & only sides got mangled by pliers...

Is it possible to OVER tighten the idler pulley bolt? (not talking about the tensioner bolt...)

As of now, later today my plan since I already have the battery disconnected, is to get some good gas in there, pull the ECU out to at least make sure there aren't any visible scorch/burn marks I may have inflicted, re-connect the battery & see if I pull any existing codes from the ECU, and then clear everything out (just to be sure) with the ECU screw.

Then, I assume I need to start the engine to see how it runs with the new gas & see if I get any new codes. At least this much should eliminate everything BUT the injectors and/or help point right at them ... will update soon ...

I take it the idler pulley bolt has the 14mm the holds the pulley on the shaft? If you didn't break it or strip the threads, it should be ok.

With a 99 model, if you are having any type of ECU problem, it wouldn't run. Trust me. I've been there and bought the dealership -- so to speak. It gets expensive fast.

If the car has been sitting for a long time, I would put in some fuel treatment. I've used Heat on a friend's Volvo that sat for over 2 years. I see people talking about good results from Sea Foam. Though fuel additives are not my strong point.

I happened to have a "brand new in the box" Phase II type injector that I just checked. The pintle caps is on as tight as it gets. Also, I checked a rail that I have in the garage and the only caps that I can rotate in the rail are on the injectors where the caps are completely broken. If there was a part that needed to spin against the pintle cap, then the cap would be a wear item and the plastic to be replaced on a fairly frequent basis.

Pictures to follow.

I actually had an ECU chip fail that kept my 99 model from running. I pulled the ECU and could not see any damage. The ECU shorting and board problem seems to be more likely on a 5th gen.

Here are some pictures of a bad ECU from my 99 Maxima. We couldn't see any issues from a visual inspection.





When I refurbished by 4th gen injectors, I tested the rails for leaks before reinstallation. I used the fuel pump on another car to run the test. All I did for the test was to close the loop so constant pressure could be maintained on the rails and injectors. I used the pressure gauge to tell me there were no leaks. This test can be performed on the car if you have doubts about leaking fuel.






On the car fuel injector testing. All I had to do was close the return fuel line to close the fuel loop and then close the supply line to prevent leak back once the max pressure had occurred.

OK, since the car WAS running and sometimes ECU damage is not visible, I opted to not take the ECU out first. I did check it for codes, even though the battery was disconnected overnight (which should have cleared any codes, but it didn't), and I pulled the Knock Sensor Code 0304, then I cleared the ECU with the screw.

Should have siphoned out the old gas first, but got antsy and just went ahead and added a bottle of HEET + about 4-5 gallons new premium gas. Cleaned battery terminals & connections ... fired up beautifully, right away, began idling VERY nicely, very smooth at about 1100rpm. Got a little rougher & lower RPM when put in Drive & Reverse, but not bad (never actually test drove it). Back in Park, let it run a little to see how things would go once everything warmed up - actually adjusted itself to a nice factory-700rpm idle all on its own after a minute or two. Everything under the hood was so nice & smooth & quiet, I had to lean in under the hood to really hear it running! I am confident now that the injector re-build went well (put the photos in a new album if you want to check them out) & everything top-end is great! And the dieseling is GONE!

So ... Out with the old problems & in with the new ...

Once the temp gauge made its way to about halfway between C&H, we smelled the rotten egg exhaust & the putt-putting began (which has been worsening since I first got the car). Already suspected I'd need to replace the cat & was on my to-do list but now I think it's a priority (especially to pass emissions). It has not yet thrown any new codes, which I read is possible if it's the main three-way cat is dying/clogged/bad ... if the pre-cats were bad, the sensors would throw a code. BUT I also read that the pre-cats would logically go bad BEFORE the main cat would, and mine seem fine, no codes. How could this be then, if just the main cat is bad?

I don't have any rattling/bees-in-a-can noise, so I don't think anything has broken loose inside ... everything down there original & pretty rusty ... I've only replaced the End Muffler/Tailpipe because it rusted/fell off & the Bank 1 Front O2 Sensor. Haven't peeked under there since last year, but I remember from when we replaced to O2 sensor how rusty & questionable the exhaust & heat shields looked. Think I'm looking at replacing from the Front Exhaust Tube Assembly all the way back to the new Muffler, including the main cat & Rear Exhaust Tube Assembly.

Looking for thoughts, direction, advice on how to maybe determine if and/or how I could possibly test/replace only the exhaust system portions that are "bad" - what my options are. I tried to research this a little, but I ran into alot of people more into tweaking their race cars than fixing an exhaust/emissions problem. Is this like doing break lines, like it's better to do all of them because the next weak point will start leaking, one after another? Is it better to replace the whole thing? Any of this unneccessary? Can I get away with just replacing the main cat section? Funds are very limited but luckily, the bf runs a machine shop and can get the car lifted up to do the work, welds, etc. Looking forward to suggestions ...

Hey Jen - Glad to see it is running good.

In my case, my injectors had been leaking for a while. So after too much fuel for too long, my cats were all cooked and clogged up. The car was nearly impossible to start. It was like a constant "potato in the exhaust end" trick.

I don't know about the pollution testing requirements in your location, but I bought a WarpSpeed Y-pipe (pre-cat delete) and a new main cat. That combination lets the Maxima breathe and perform better than the stock setup.

I think member Turbobink replaced cats on his 99 model. Maybe he will stop by and post some info.

I'm a determined gal Stayed up late, logged a few hours poking around here to try to teach myself all about the exhaust system & here's what I think ...

Everything sounds sweet up front & even the exhaust is pretty quiet when the car is cold, start-ups are instant & very strong ... issues start when it warms up: idle not as strong or smooth & the light white smoke and putt-putt from tailpipe, worsens under load with brake on, revving rpms in park is strong and smooth. I also realize I am still working that old gas through (there was still about 1/4 tank that I left in there).

I do not hear, see or smell anything under the hood to make me think there are any exhaust manifold leaks - the putt-putt sound seems to originate at some point between the front & back tires. I agree with you CS - this car was run so dirty for so long before I got it, lots of carbon & varnish, injector & coil issues since I've had it, I'm sure my main cat is cooked as well, but that the front O2 sensors & pre-cats are good with everything I've cleaned, checked & replaced up front, which is why I'm not getting any new O2 sensor codes.

No hissing under car like exhaust leaks & it seems all the exhaust is coming out the tailpipe, nothing visible coming from underneath the car, but I'm gonna jack it up to get a good eye on things down there - want to see if I can get away with only replacing the main cat (found for $105 on rockauto, not bad) & possibly the flex portion as I hear that piece is first to fail alot.

I found that main cat issues pretty much aren't supposed to affect engine performance unless it's clogged or close enough to create backpressure, which I can't see being enough of a problem because there is a good dead of pulsing smoke leaving the tailpipe.

Another discovery - I need to replace the Knock Sensor - duh. I got so used to ignoring the KS code because it was always a companion to other codes BUT I got it alone this time. Without a functioning KS, the ECU is putting the timing into safe mode (and I had a wise friend say "it sounds like a timing issue" at one point) - all makes sense & found one, again on rockauto, my fav, for $25, cool.

Somehow, trying to research the idle changes & roughness, I kept running into fixes by "grounding the MAF" - then I got all kinds of sidetracked learning about grounding issues. Don't worry, I'm not going out to buy a slick "grounding kit" - I have not souped up or changed any of the electronics, just looking for function. Plus, because there was such a mess around the UIM & Valve Cover Gaskets when I started all this, the 2 ground wires that connect between the front injectors are most likely affected too - I am going to clean up those grounding connections and have the bf help me run a ground from the MAF - I think/hope that's as far as I need to concern myself with electrical issues.

My back-up, shared vehicle is acting up, so I need to take a small pause on my car to take care of his (99 Silverado Pickup), plus I have bills to pay & need to work like everyone else to get the funds up to finish the work on my Max. I welcome any input on my plans concerning the exhaust (thanks for yours, CS!) in the meanwhile. I will of course update again soon & I guarantee it will not be a year-long break this time ... I'm too close!

Before I pulled the car out of the garage, I went ahead & cleaned up the ground connections on the FI rail. Hadn't really run the car since the last work was done, so drove up & down the alley a few times before parking it back outside for the small "break". I was actually thrilled to see the CEL on... Yes! More clues!

3 CODES this time: the Knock Sensor again (0304), PLUS the two codes for the OTHER Front O2 Sensor (0901 & 1001, Upstream, Front Right, Bank 2, by the Radiator). I had already replaced the Front Left, Bank 1 by the Firewall last year due to getting the specific code for it then. My sense of logic & troubleshooting finally made sense ... it was really puzzling me why I was getting symptoms of a bad Main Cat without having thrown codes for BOTH Front O2 sensors, which should logically fail before the Main Cat from what I've read. My favorite part of this new news is that right from the FSM regarding the function of this Sensor, it says it send signals that affect how the ECU decides to fire the injectors - this ends my question about if a bad Main Cat can affect idle, so now I'm excited that the new O2 might fix the last of my idle concerns.

Because I have not gotten any new codes from the Bank 1 O2 Sensor I replaced last year, I assume that Pre-Cat is functioning ... I am hoping for the same results when I replace the other one in Bank 2. If that happens & both my Pre-Cats seem to be holding, I might skip past the Y-Pipe section altogether, especially if I don't have manifold leaks, the flex pipe seems to be holding, isn't leaking (yet) ... just swap in a new Main Cat to make sure I pass Emissions Testing (Indiana) & to stall off any additional wear/damage to Exhaust & Pre-Cats. It's pretty darn rusty under there living here the Midwest, so the less nut busting, the better. If money wasn't an issue, I'd just replace the whole exhaust and be done, of course.

Re-summary: KS + O2 Sensor should finally take care of timing/idle issue. Hopefully, new Main Cat will take care of the "putt-putt" & get me through Emissions. Still going to have the bf ground the MAF too. Until then, fingers crossed...

It's shopping day! Ordering the KS, O2 Sensor & Main Cat so I'll be able to post an update soon!

A worthy bump ... the bf is selling his truck I've been driving as back up, so he closed the deal by getting enough extra to cover my parts, since I will now need to get it back on the road asap ... the last "break" in working on my car was a year, so 6 months since my last post is quite an improvement lol.

I have good tools to replace the KS & the bf already assisted me in replacing the Front Bank 1 O2 Sensor (replacing Bank 2 by the radiator now), so we know how that goes. Any specific advice or video on replacing ONLY the Main Cat section of the exhaust?

Already replaced the Tailpipe, Muffler End (original fell off lol)... Everything rusty & flaking but no hissing or apparent leaks ... Flex section seems to be holding for now ... Working on a bare minimum budget to pass Indiana emissions ... Pre-cats seem ok, still no code still from recently replaced Front Bank 1 O2 Sensor, replacing Bank 2 (which I am now getting a specific code for), assuming same results ... that leaves the Main Cat.

Thanks in advance for any help & wish me luck ... I'll be updating with photos soon ...

hmm....

other members have mentioned Maxi Pads before. They had a different meaning though....

As a girl, you would get it.....

Glad that you are making progress.

New update ...

OK, got the new Main Cat in, new Knock Sensor in, and the second front O2 Sensor replaced.

STILL have the 'rough idle under load" issue BUT more clues at least. Did the sensors myself but ended up taking it to a muffler shop to swap in the new main cat cuz the rust was just too heavy. The guys there were impressed enough with the laundry list I've worked through on this car to give me their opinions ... said it sounded like a mis-firing, which I've heard from other people ... the flex pipe is holding, no leaks there, but where the replacement muffler end was installed, it's not attached/sealed so it is putting out of there a little (should be a simple remedy, so not so worried about that).

The car fires up great every time, no apparent electrical issues, nothing different from all the work I've done, runs great, EXCELLENT acceleration ... just the idle drops/bogging out (never completely dies tho) once warmed up, when brake on in gear. First test drive after these last 3 items were replaced, several times around several blocks, no highway, no CEL, everything great but the idle issue did creep up once it warmed up, never while actually driving, just when idling with brake on, like at a stop sign or stop light. Went to start it back up a few days later to take it for emissions testing and boom, the CEL popped on before I even put it in gear ... P0505 ... IACV.

So what can cause misfiring? All new coil packs & rebuilt fuel injectors, battery good, no starting or dying issues so ECU seems to be ok. I already cleaned the MAF with MAF cleaner, but still wanted to run an extra ground wire which I haven't done yet. I already cleaned the EGR tube & ports, and the throttle body. I read that the Knock Sensor and/or the O2 Sensors send feedback to the ECU that can make it decide to run in "safe mode" but those sensors are all new now. All that being said, the IACV would seem to be the only possible culprit remaining ... the issues of spark & fuel are non-issues, so it's gotta be air ... MAF grounding might help, can't hurt ... re-used all original gaskets on EGR, TB & IACV, and could need TB adjustments, but the code was specific to the IACV.

Original IACV was filthy so I cleaned it, but ended up swapping in a junkyard replacement, which I also cleaned ... my logic was if I had an idling issue, the Idle Air Control swap was a worthy, inexpensive test-swap, but it's possible they're both toast, or the gasket needs replaced and they're both fine. I've read enough IACV threads know to know there is not an idle relearn process for 4th Gens , but there is a simple start-up procedure that involves removing a plug so things can start fresh. I need to do that next, and see how to test the IACVs I have to see if they're good, and maybe even buy the gasket before forking over the $ for a whole new unit. Gonna take a look at the TB cables & contacts to see if everything looks right.

Any input or thoughts are welcome ... I'll be back with an update soon ...