2003 Maxima (original owner), 285,000 miles, regular fuel for its entire life. New NGK spark plugs about 3,000 miles ago.
Suddenly while driving at least 50+MPH the engine started pinging really bad (it's always had just a little spark-knock with slight gas pedal pressure) but is severe spark-knock. Engine lost allot of power, barely being able to climb a big, long hill (I live in CO at 8700 FT elevation so used to a typical 25% loss of power due to altitude).
Engine starts great, smooth idle, runs somewhat OK (no severe pinging) (but noticeable lack of power) until pulling hills on top gear. I can hear the engine intake "groan". SEL was blinking for a while, then went off. SEL blinked during each outing but when off. Autozone couldn't read code because SEL was not on at the time. Later in the day, the SEL came on and stayed on - Code is PO300 "multiple misfire" but I do not feel misfires. I replaced air filter, added Techron total fuel system cleaner to 1/2 tank of gas, no change. Sprayed starting fluid around vacuum lines (with engine running), no change, so likely not a vacuum leak. Vacuum actuated butterfly valve on passenger side of intake plenum, has a very slight squeak and bind right at 90% full open
I do not want to put a bunch of $ into the car since it's not worth it. I hope to fix this myself. Hoping it's something easy like ping sensor or crankshaft timing sensor.

 

My first guess would be clogged catalytic converters, that plus 87 octane gas would make it worse. I think P0300 is what you get when the engine struggles to stay running before it stalls out. if the engine light is blinking steadily you have a misfire. they should be able to pul a code even if the engine light goes out after being on.

I live in central Florida and during hot summers my car gets bad pinging when sitting in traffic or parked for a while with A/C on and I have all the cats removed and i only run 93 octane

 

Hello!
New NGK Platinum spark plugs about 3,000 miles ago and new plenum gasket. Sprayed starting fluid all around vacuum lines - no change in rpm. Put new engine air filter in
I have run Cataclean through it. Now in the tank (premium octane) and a bottle of Dura Lube Severe Catalytic and exhaust treatment. I have seen no difference in performance yet. Engine has severe loss of power. Starts idles and revs smoothly in (AT)-neutral. Low power until about 2500 RPM. Above 2500 RPM it just bogs, some slight misfire felt. (did a code check with blinks on SEL = 300 - multiple engine misfire) Runs fairly OK downhill in top gear. As soon as I come to a hill and downshift happens (causing RPM above 2500 - severe bog and won't go over 40 MPH with a lot of what sounds like "ping-rattle".
Local (independent) shop says clogged cat(s) typically don't cause multiple misfire code.
Any more thoughts?

 

Inspect and clean the coil to coil boot interfaces and inspect the coil boot internal springs.

Replace the knock sensor.

 

Blinking CEL is a dead giveaway that you have one ore more bad fuel injectors. This would cause your multiple misfire code.

 

When you said regular gas its whole life, (Red flag)! Catalytic converters are probaly done for, engine cannot breathe.

 

I assume at 285k, you would have replaced all the ign coils. But have you replaced the ign coils within the past 100k? For me, bad coils usually start with a blinking SES followed by constant SES and P0300 thru P0306 code(s) indicating the specific cylinder(s).

 

Yep, I'm amazed it didnt die 100k ago. Cats are borked.

 

Here is what I've done - replaced fuel pump and fuel filter, removed and cleaned rear cat with lacquer thinner (I could see through cat before I cleaned it), cleaned and tested all under hood grounds, replaced broken trans ground wire, replaced knock sensor with genuine Nissan part replaced spark plugs, replaced fuel injectors, replaced ignition coils, had battery tested.

Noticed - rear bank (near firewall) spark plugs came out with black tips. Front bank plugs were normal tan colored.
Test drive after new parts. NO change - still severe loss of power (the more you press the gas pedal down more the more it bogs and slows). Engine intake really makes a loud ("groaning" sound) way more than usual, especially the more you press the gas pedal down
Blinking CEL Code - 0300 - random multiple engine misfire. This is the only code flashing so it's really not helping me find the issue.

 

what brand ignition coils? Our cars are finicky when it comes to them. Hitachi is the preferred brand (oem supplier).

 

It is extremely unlikely that it's the non-Hitachi coils since there was absolutely no change in how it runs before and after the new coils (which unfortunately tells me that all the new parts I put in have been a waste of time and money). I also still have the OEM coils I took out.
One of the only things I haven't done is remove and inspect the pre-cats (which I have put off, hoping it was something else (easier) because the thought of crawling under a car again at 69 Yrs old with arthritis, is dreadful). I am now suspecting it's the bank 1 (firewall) pre-cat because the spark plugs were black when removed from bank 1

It's kind of ironic - I was planning to sell my Maxima because I just bought a more practical used 4x4 SUV for up here in the mountains of Colorado. It was running good before this issue. Whoever buys my Maxima will be glad to have a bunch of new parts on it.

 

So I have replaced, knock sensor, fuel pump, fuel filter, ignition coils, fuel injectors, spark plugs, then removed the rear cat and found a bunch of crumbled cat bits plugging up the rear cat. I cleaned out all that ,and cleaned the rear cat with lacquer thinner. You can see through it even better now but wasn't bad to start with. A while ago Nissan said that my bank 1 (firewall) pre-cat was rattling (loose innards). Well the cat material has been slowly breaking up (crumbling) and getting caught at the rear cat. The honey comb material that's still left in the bank 1 pre-cat must have eroded enough to turn sideways and block flow. I did notice when I replaced the spark plugs the Bank 1 (firewall) plugs were black (the bank 2 plugs were normal tan color).
The engine runs a bit better, starts and idles fine (no ping now) but still has loss of power. Replacing a bank 1 pre-cat is too big of a job for me (I'm almost 70 and not so agile under a car these days, so I've (sadly) decided to sell it.
It looks like someone could remove the "Y" pipe and remove the obstruction in the rear pre-cat without actually having to remove the pre-cat.
2003 GXE with rear spoiler. I'm the original owner, serviced per manual. engine oil every 5K, trans every 30K. never wrecked. 285K miles but 90% is highway miles (drove it for work in a multi state sales territory). Always garaged - body shiny (color Sterling Mist) and just a couple door dings and some scuffs on rear bumper. Brakes and tires good at about 50% wear. CV boots good. Interior clean and no visible wear. Ran great before this issue
Hoping to get maybe $1200?? KBB says $1805, Edmunds says $2297 (if running properly). Can drive/deliver it in the Colorado Springs/Denver CO region, just won't go to highway speeds, so I'll drive back roads since it won't go much over 50 MPH
What do you think I can sell it for?

 

Before you give up on the old girl, you may want to consider replacing the MAF with a good used junkyard MAF.

For price, I'd start at $2,000 and negotiate down a little if need be. Used car market is still hot right now.

 

Just curious (and certainly not an expert) - Wouldn't a faulty MAF affect both engine banks? It starts right up and idles fine and runs ok until about 2500 RPM. beyond 2500 RPM it begins to bog (intake making a bogging/groaning sound) and then the SES light comes on, code 0300. (I reset the ECU just before this test)
The only code I get is 0300 (multiple misfire)
Looking at my spark plugs, the right (front #2) 3 plugs are the usual tan color. The left bank (firewall #1) 3 spark plugs are black and this is the bank that has the rattling pre-cat (catalyst has broken up and become loose enough to rattle inside the cat housing). I cleaned out a bunch of broken-up catalyst pieces from the front (entry) of the rear cat, that had to have come from the rattling bank 1 pre-cat. It just seems like bank 1 (firewall) is running rich (black spark plugs) because the air flow is super low (I'm ASSUMING that the pre-cat honeycomb holes are no longer aligned with the exhaust flow direction (honeycomb holes tilted sideways because so much catalyst has broken off, no longer keeping the honeycomb holes oriented with the exhaust flow direction).
If I could find someone to do it - remove the "Y" pipe and flex pipe assembly (since the rear cat has new bolts and easily comes apart) and expose the exit opening to the bank 1 pre-cat, remove the "restriction" (with maybe a 1-1/2" blade type drill bit busting it into bits small enough to fall out) and see if that helps

I'm not sure if a MAF from the junkyard would be good or not. Is there a way to test them? Maybe I can test the original one I have in there now? I did clean it (no improvement) and the throttle body while I was in there (no improvement)
I've heard to not use aftermarket parts that are talking directly to the ECU (like knock, crank, cam, and maf sensors) BUT has anyone had good luck with an aftermarket brand MAF in a Nissan?

 

+1 not a bad gamble to just try another maf, also if you really wanna commit you need to gut the precats, and get an O2 bung extenders (1 for each pre cat) so you dont any codes , and just like you described once off u just use a spade bit and remove everything, I did it 2x

your description is exactly why people gut the precats in the older age of these cars the material breaks apart and also can go the opposite direction into the engine.

I gutted my original precats at 175k and luckily all the precat internals were in tip top shape when i went to gut them so I knew I was in the clear and would be even safer after I gutted them.

 

Gutting both pre-cats is way too big a job for me (don't have the right tools, don't have the right body to be laying/twisting under a car for hours-(almost 70 with arthritis). Unfortunately I don't know anyone who would do that for me. I'm also not willing to spend a couple grand for a shop to install new pre-cats
I suppose I'll have to sell it as-is. Very sad

 

OK, I'm going to try a new MAF sensor. Can anyone recommend an aftermarket MAF sensor that isn't too expensive that someone has had some successful experience with?

Just drove it. It runs a little better now (but not good) since that I cleaned out the crumbled catalyst (from the bank 1 pre-cat) that loaded up the face of the rear cat. It seems to to really bog down dependent on throttle position. Just a little throttle, it doesn't run too bad, but a little more throttle (like going up hills) and it bogs and groans and slows. The new MAF is my last attempt. I guess then, I'll just sell it as-is

 

I'd stick with a used OEM MAF rather than a new aftermarket MAF. If you can't make it a junkyard, there is always Ebay.

 

How does the junk yard test it to make sure it's good?

 

They don't test them. You pick and pull the part, then pay for it. Most cars in the jy are in the jy because of an accident. Besides, what are the odds that the car was junked because the MAF failed causing the car to become undriveable? You're over analyzing this.

Some junkyards offer a 7 day warranty/exchange.

 

Sorry for over analyzing - I'm just about done throwing more parts at it with no positive results (very frustrated). Based on Maxima.org forum recommendations, I just put in: new knock sensor, new fuel pump, new fuel filter, new fuel injectors, new ignition coils, new spark plugs, cleaned all grounds, cleaned rear cat (breaking off studs and drilling them out).
But Ebay does have several used MAF sensors to choose from. Thanks for the suggestion!

Could a bad MAF cause one bank to run rich and the other bank normal?

 

We hear you and understand your frustration. A bad MAF would not cause only one bank to run rich. Previously, when you said only one bank was running rich, I would attribute that to failing injectors, which ties into your original post of the flashing CEL (see my previous post). But, you changed the injectors. Hopefully you put in good working injectors. Don't assume that new parts as working perfectly as they should. Don't rule them out, they could still be bad. I once had an injector issue (multiple misfire, white smoke out of exhaust) proceeded to replace all 6 injectors with OEM refurbished injectors, only to find out that the car ran better, but not perfect. One of the new injectors was bad. Once I replaced that one injector a second time, car ran smooth as silk.

When you say it's fine at low speeds but struggles once you put your foot down and begins to bog, that's usually a sign of bad coilpacks. But you replaced those too. Doesn't mean that you still have one or more bad coilpacks though....

And since you replaced the injectors and coilpacks, that led me to my suggestion of replacing the MAF. A bad MAF will cause the bogging you described too.

It is my hope that you installed OEM coilpacks, OEM injectors (new or refurbished and flow tested) and OEM NGK spark plugs...

Good luck and keep us posted.

 

Sorry for being so needy. You have been extremely helpful. Thank YOU!
Looking on Ebay for a maf sensor. I find several that say they fit a 2003 Maxima BUT they don't look like the original I have. There is no part number on my original. It is all plastic - no visible metal plates, fastening flange is all plastic too (no metal screw 'tabs")
The only pic I've found that looks exactly like my original is here: https://www.nissanpartsdeal.com/part...tra2=&filter=()
Attached is a pic of my original
Do you think I can trust that this one on Ebay is correct for my 2003 even though it looks different? https://www.ebay.com/itm/31404473073...Bk9SR6LksY31YA

 

I agree. The car will have issues with non NGK plugs and non-OEM coils like Hitachi.

 

I would definitely not trust the MAF sensor in the link above. There should be a stamp or sticker somewhere on your existing MAF with the model number/part number etc.

 

Based on your first link, I entered in the part number into Ebay. This is what I came up with. Looks like the one you shared in your two pictures...but it's aftermarket.

https://www.ebay.com/itm/22322240422...3ABFBMkJOOnPVg

Here's OEM $40 to $50 is about the going rate for a used OEM MAF. Make the Seller an Offer! Returns are accepted.
https://www.ebay.com/itm/16569818675...Bk9SR5CTjpz1YA

Here's another one. 90 day warranty. Free returns.

https://www.ebay.com/itm/15518419080...3ABFBMxPStnPVg

 

So I bought the good, used OEM MAF sensor. No change in engine performance. Starts right up, idles good, just has no power over about 2500- 3000 RPM
I think I have replaced all the possible causes (knock sensor, air filter, spark plugs, fuel injectors, ignition coil packs, cleaned rear cat, fuel pump, fuel filter - all with no change) EXCEPT I did not mess with the firewall-side pre-cat which has been rattling (loose honeycomb innards, per Nissan dealership) for a several years and I cleaned out a bunch of crumbled honeycomb catalyst out from the face of the rear main cat.
So, my suspicion is that the pre-cat innards have crumbled enough to allow whats left in the housing to fall over and mis-align the honeycomb holes kind of sideways, so not much flow can get through, essentially choking-off the firewall side 3 cylinders from enough combustion air causing those 3 plugs to be running fuel rich (those 3 spark plugs came out with black sooty tips) resulting in code 0300 (multiple misfire)
I do not have the tools (impact wrench) (and drilling out broken studs) the flexibility/endurance (I'm 69 yrs old) when removing the "Y" pipe (which allows access to the bottom opening of the pre-cat to knock-out/drill-out the remaining loose catalyst "puck". I also found a new identical pre-cat on Ebay for $100, but that's an even bigger job for me.

So, I'm going to sell it. Ideally to someone with the tools to fix it themselves (remove "Y" pipe, drill out cat material, put a bung spacer on the O2 sensor)

What do you think is a fair asking price? I live a little west of Colorado Springs CO
I'm not sure if it's a good idea to drive it very (to deliver it, if necessary)