90sWheels

After a short drive, warmed up to 84C, I took these pics of my scanner. I don't understand why there is an extra section on short-term and long-term fuel trim.

this looks pretty good


but this looks weird to me

I have watched a few YT videos about fuel trim so I have some idea how it works. A guy said that a rule of thumb is if is LTFT +/-10% you are pretty good. It's the "SHRTFT12 - 99.2%" that has me worried.

I think the O2 readings didn't change much unless I revved the engine. I hear they are supposed to oscillate or something.

Other readings
MAF: 5.71g/s
MAP: 31.0kPa
Spark Advance: 15%

I have a knock sensor code that keeps coming back. Emission codes come up sometimes. There is a humming noise that is hopefully the FPR (as per post in my coolant flush thread).

Thanks for reading.

Turbobink

iTrader: (2)

Other than the knock sensor DTC, what issues (drivability or otherwise) are you having?

Zerodrag

iTrader: (1)

Aren't they just representing the separate readings from bank 1 and bank 2 of the fuel trims and O2 sensors?

90sWheels

The acceleration at low speed/rpm is underwhelming. Also the last time I checked the fuel economy - before I did a tranny drain-and-fill - it was not very good. It was about 20mpg mixed town and highway (on OD, 110km/h; OD off for town, of course). Though maybe I did a fair bit of town driving. It could be that the mileage is better now that the trans fluid got renewed.

Also, going up a long steep hill near where I live the car doesn't like to go faster than 40-45km/h, while the other newer cars behind are pushing. If I open the throttle more aggressively it downshifts but the speed doesn't increase much, if at all. Is forcing a downshift harder or easier on the tranny in this situation? Tough thing is the car has to tackle this hill pretty much every time I leave home, and it's been doing it for 14 years (since before I owned it).

Once driving on the highway with OD off, around 80km/h, the car feels pretty responsive. I am aware that 4th gear is the most direct connection in the transmission, so maybe there is some slippage going on in the earlier gears. But also, vacuum leaks tend to be less noticeable with the throttle open if I'm not mistaken.

The car needs all the usual TB, IACV, MAF, EGR etc cleaning done and injectors serviced before they start causing trouble. It's a '97 with 265k kilometers (164k mi) on it. I finally understood fuel trim so I wanted to take a look at how Maxy was doing. If it really is +99% on one bank then that would cause problems, right? I guess I need to get a propane torch to test for vacuum leaks.

Oh, I realized that I should have taken the fuel trims at 2500rpm as well. Next time.

Other things of note:
I run TC-W3 in the gas most of the time.
I was using premium gas but then I went to econo when the prices surged. I might go back to premium now that cold weather is here (and I don't drive much anyway).

Turbobink

iTrader: (2)

So, other than the knock sensor DTC, no other codes have been stored, correct?

Also, the knock sensor error appeared before, during or after your use of the lower octane fuels?

KP11520

Bad Knock Sensor (Truly BAD) Certainly causes an under powered response. That's what it's supposed to do to HOPEFULLY save your engine if something internal starts slapping around.

If it's original, REPLACE IT as it owes you nothing at 265K. Some have gone through two at that kind of mileage. And if you have no other codes and it's repeatedly, it's usually not a false alert.

FPR also owes you nothing at that mileage. But a humming noise? Didn't think that would be a symptom of one on its way out? But who knows? TPS does that when bad or not adjusted properly. Have you ever replaced your fuel filter? Or Fuel Lines? Have you ever cleaned your EGR tube? Probably a good idea if all original! In fact, a whole intake refresh is a good idea! if never done.

So many questions with that much mileage and pretty much zero info on the service and maintenance history of the car! Or.... Any car!

90sWheels

Yes, I am a bit of a rookie when it comes to wrenching and car owning - at about 40. There is much to be done on this car but, unfortunately, I don't have a garage and it rains pretty much every day for 2/3s of the year around here. Also funding is very tight. So doing that whole refresh routine is a goal of mine but it will be in God's hands whether it can happen or not.

I already have a new FPR and all the gaskets I need. Refurbished injectors are the next pressing cost. Probably my next move is to try to unplug the old knock sensor and mount the new one I have somewhere on the plenum to try that out. (I don't have much confidence that I can mount it properly. It might be a Cali-spec, not sure.)

I'd like to do another trans DaF at some point too, as I only did one in the 20 months of ownership. There was a receipt for a Jiffy Lube trans flush 12 years ago, so maybe it's safe.


@Turbobink , I think the knock sensor code has always been there. Gas quality has no noticeable affect on how it drives right now. A code for air temp sensor popped up, but I think that was just because I didn't bother to unplug the battery when doing the coolant flush. Predictably, EVAP codes arise here and there.

90sWheels

Here is why I think it might be the FPR that is causing the humming sound.
https://maxima.org/forums/4th-genera...ml#post9249551
It was not present before I updated my cooling system

No, I haven't replaced any of the small lines on the engine, just the radiator lines. It's a bit of a trip to get to the Lordco from here, I go to Town about once a month only. That is part of why I was interested in fuel trim numbers.

Edit: Yes, the fuel filter was changed 20 months ago. No, no fuel lines have been changed. Thanks for the tip about the TPS - will read up on it!

KP11520

If your car is a Canadian Maxima, you just might have a VLSD transmission.... NICE!. There's an aluminum plate on the firewall in the engine compartment on the passenger side. Third or fourth line down has a number for Transmission type:

If it has an "A" you have an Open Drive". One wheel Drive.

If you have a "V", you have a limited slip. Meaning both wheels turn by the engine power at the same time. SO Much better in snow with GOOD tires and all around handling.

Get that knock Sensor and Fuel Pressure Regulator done. Hopefully you used an OEM Regulator of equivalent like Standard Motor Products. RockAuto, if they ship up there, is a GREAT resource. Look for their 5% Discount codes that are always in effect. MotorMan Fuel Injectors sells an OEM rebuilt and matched Fuel Injector lit for $129.99.on eBay. All six and matched. Get 6 new Grommets (Felpro) and six new insulators (Cushion between the top of the injector and metal cap holding them in place). And all new screws for the injector caps and FPR as well. Stainless with washers and Allen Key heads. Use Antiseize compound on all the threads.

90sWheels

@KP11520 Thank you for the links and advice
You made me search through my photos to see if I could find a picture of the serial number (car is 500ft away) - alas, to no avail. From what I remember though I just have the plain version. The serial number should tell about Cali-spec too, I would think, but somehow it evaded my interrogation last time. I just thought that the valley looked pretty damn tight ... I do have some swivels and extensions now, so I might take a whack at it

I guess mounting the KS in an ad-hoc (wrong) position risks the engine damaging itself eh? The KS I got was just a cheapie on eBay as well... another risk, I suppose

Turbobink

iTrader: (2)

There is no need to find an alternative location to mount the KS.

The removal and install may be challenging but it’s unquestionably doable with a combo of socket extensions and swivels … I’ve personally done it three times on my ‘99 alone, not to mention assisting others with theirs.

Albeit, I own a Fed-Spec, I can’t imagine the situation isn’t the same for a Cali car.

Also, you say cheapie KS … what does that mean? There are some well known/quality brand units available for no more than about $50.

KP11520

There's one way to get your car running properly.... DO IT RIGHT!

If you have California Emissions, the only way to replace the knock sensor is to remove the Upper Intake Manifold,, and Lower Intake manifold. So, you'll need all three gaskets. USE A QUALITY KNOCK SENSOR. After taking the car apart to that level, you don't want to do it again EVER! Cheap ones usually guarantee having to do it again sooner than later. If you're going in that deep, might as well do an entire Intake Refresh. New gaskets, Injectors and related parts, PCV Valve, Vacuum and Fuel Hoses (High Fuel Pressure 3/8" type) and Clamps, EGR Tube cleaning and gaskets, and so on! And at least do the rear Valve Cover gasket with the Right Black Oil Resistant RTV to prevent leaks while there. Imagine getting a new leak a month after doing everything and having to go back in to address that? Rear Valve cover leaks have been known to ruin other parts of the engine, so don't ignore that.

Are you ready to invent some new curse words? Perfect job for that creative flow! LOL

90sWheels

I do have all the gaskets I need, I think. I bought them a year and a half ago, following advice from you guys. I got Fel Pro. Yup, RTV and PCV valve and grommet are in the box of parts already. I know about the special screw head on the injectors and that I can grind the tip off a normal Phillips. I am a bit unclear about the insulators for the injectors - I already have one new pack but it sounds like there is 2 different sets that need a refresh. I'll probably work on the front bank first and that way things will be clearer before diving into the rear bank.

Pulling out of the driveway today the cold weather reminded me that the steering pump and pulley need replacing: *squeeeeeel!* (A whole nother can of worms that I remember is a nasty one).

Okay I found the photo of the tag and, yes, It's a Canadian model
It's pretty amazing how many different colours of this car they produced (and different trims too).

Yeah, I think the KS was about 35cad on eBay. I remember people on here saying they had no problems with it. But there are various opinions in past threads. I guess if it doesn't do the job the ECU will just stop listening to it and throw a code?
Edit: I got this one - less than 20cad!

To be able to do the big refresh job I will need to finish my 2nd wood shed and clear junk out of there. This will give me at least a fighting chance to work, protected from the elements. And I have to find a way to earn some extra dough to afford parts!

JvG

You mentioned a squeeling power steering pump.

Sometimes a fluid change makes a world of difference.
Please dip a bit of paper towel or cloth into the tank.
What color is it. Describe the smell.

if it looks and smells like automatic transmission fluid, all is well. It should be red or salmon color.
it should small like ATF. It should not be dark brown or black. Should not smell burnt.

Regarding your MPG . A US gallon is 3.785 liters.

I've seen some calculations about liters per British gallon . They use different math than we do in the US.

Most of our members live in the US.
We are used to our old archaic measurement system rather than metric. Please convert metric measurements to US measurements. That helps us help you. I know what you are talking about though.

When climbing or decending a steep hill Noth the engine and the transmission really appreciate you going into a lower gear with thr gear shift ever You will find that your engine is more responsive. Other cars which pass you are most likely I'm a lower gear. Such as 3rd or 2nd gear.

Do you know if the gas filter has ever been replaced?
I like to replace mine at least at 100,000 km intervals.
If it hasn't been replaced. Do so soon. You might be pleasantly surprised with the outcome. I always try simple and obvious preventative maintenance first.

Turbobink

iTrader: (2)

This being the case, I retract and apologize for my previous admonishments regarding “do-ability” as I apparently don’t know what I’m talking about.

KP11520

YUP! When it comes to Cali Spec models and KS replacement.... It's Not "California Dreamin"

More like California SCREAMIN!

KP11520

When a true Knock Sensor code keeps coming back, and it's not a ghost code behind another problem, the ECU is supposed to put limiters on the engine and mute its performance to lower the chance of blowing the engine, if you have internal parts that are sloppy and about to break, causing that knock. You mentioned sluggish performance? Well... There it is! Knock sensor gave up the ghost or a REAL knock. But odds are in your favor it's the sensor.

My PS pump was replaced with 100K less miles than you have. JvG is right to suggest you dig deeper SOON to find the cause of the squeal. Hopefully, just the old cracking belt and all that humidity is the cause. But either way... SOON! Burnt PS fluid isn't good for the PS Rack either, or any seals in the loop.

90sWheels

@JvG , yes the fuel filter has been changed, right before I became owner ~2 years ago. I might replace it again if I clean the TB. It's a tight area so access will be easier with stuff off. Thanks for the tip about downshifting. I remember I used to do that when I was younger but I lost confidence that it was a good idea and my net search came up empty.

I have flushed the steering fluid from the reservoir 2-3 times now. The last time I did it when I was in the middle of the coolant flush because I was thinking that I might replace a small steering hose that is wet with fluid. It became apparent that my plate was full just with doing the coolant flush, so I backed out of that and re-filled the reservoir. But because I was on ramps I had difficulty judging the level. It turns out that driving to the hill to do the burping I was a bit low on fluid, so that was probably bad for the steering system. Could it be that air is in the steering system now? That poor pump took more abuse, unfortunately The steering squeel mostly just happens in cold weather with a cold car. But yeah, it wants changing. I guess it couldn't hurt to do the flush a couple more times. The fluid was nasty at first but it's getting better.

The steering squeel is a known issue but the humming sound that appeared after the coolant flush is more mysterious and concerning. Hopefully it isn't a transmission bearing, and just the FPR. (I have yet to find reference to TPS causing a noise, btw, @KP11520 ).

@Turbobink I was mistaken: it's Canadian. Doing the coolant flush familiarized me with taking off the air ram (it's easy!) so that should help with the KS replacement. Those plastic gromets at the front of the air ram were easily replaced with solid copper wire (old electric cable lying around).

I found my old notes from 2 years ago on mileage. Using the conversion factor of 2.352 from this website I get 22.2mpg. Not bad (I have bigger problems!). I shall re-do the test when possible.


I had another look at the fuel trim numbers yesterday and they didn't change appreciably upon revving. One O2 sensor was oscillating while the other stayed still.

KP11520

90sWheels

Aiite, I be checkin' it

Turbobink

iTrader: (2)

I’m not clear as to the differences b/t a Canadian model and a California-spec US model, if there are any.

Regardless, and this is point I was making previously, if your car is the equivalent to a Federal-spec US model, there is no need to remove anything in order to replace a knock sensor … except for the old knock sensor, of course.

90sWheels

Edit: You mean Canadian might as well be Cali-spec? Looking again the aluminum tag I divine that the transaxle is not the special type, just a regular open one. I will attempt the KS change soon. It's a bit cold out at the moment, and I had to deal with apple trees today. The raccoons come around for the winter keeper apples and in the process they menace the cat. So I knocked them all down with a stick.

JvG

The car will run the same whether the knock sensor is replaced or not.

The cause of your problem is something else.

fix the other things first.

I say this because replacing the knock sensor is a pita.

chances are that you might have a bad injector.
if so, you might need to remove the upper intake manifold. The knock sensor is real easy to replace once the uim is off.

A bad knock sensor means that the car will not be able to advance timing to take advantage of premium fuel.
That's about all.

unless you drive this car a lot consider delaying work till next spring. Save up so thst you can have the injectors rebuilt, change the valve cover seals, work on the egr, install tge knock sensor. It's all a considerable
fluster cluck. All much easier when the upper manifold is off. Do it all at one time.

I had a bad mileage issue for years. On a whim I decided to replace both up stream oxygen sensors.
my mileage increased considerably.

I didn't own a scanner at the time. So I could not measure ant differences before or after fuel ratios

90sWheels

Thanks for the encouragment, @JvG . I hear what you're saying. The car did have a gassy smelling oil a while back but since I've been more mindful about trying to get more errands done in one day I think it has gone away. I heard that many cold starts can contribute to the gas in oil thing. But yeah, it definitely sounds like injectors on the 4th Gen have a limited lifespan. I'm driving on borrowed time

Attempting to change the KS shouldn't be a big deal, once I feel up to it. The worst that could happen, I reckon, is having to go fishing with a magnet. I'll try not to lose any knuckles.

Yup, I gotta save up them loonies and twonies. I asked someone today if he was hiring

Today I tested my TPS with the multimeter and got 0.8 closed and 4.5 open (I guess kOhms). It was 0C outside today and the FSM guideline is for 25C. I would think that the resistance should have gone down in colder temperature, but I don't know. Am I out of spec?


Driving The Big Hill today didn't seem slow this time... but maybe last time I was loaded down with 200lbs of cargo. Downshifting into 2nd going down felt interesting, definitely easier on the brakes. Dunno if the fiddliness is worth it for a hill this length though.

JvG

Get used to downshifting when going up or down steep hills. It's safer going down hill, Also much kinder to your transmission and engine bearings. Your car will certainly perform better going up and down hills.

Let's review.... I think you replaced spark plugs.
Our engines really want the NGK ones.

have you cleaned your Mass Air Flow sensor and your throttle plate yet.

90sWheels

Yes, I did the spark plug change a year ago and the simple NGK ones went in (the same thing came out, as well). The MAF and TB do look to be the next low-hanging fruit. It's been a while since I studied up on how to clean the MAF. A video that CarsNToys did indicated that there is a film to go along with a wire. Am I to not touch both objects, but just spray them? I will be using a respirator and other safety gear.

I will continue trying out the downshifting technique. One thing that has me a bit leery is that the feel of the shifter isn't that definite when you shift. I don't think there's anything wrong with mine, it's just that I don't want to make a mistake. Also I wonder if I have to be concerned about what the engine rpms and wheel speed are while shifting. I have driven stick but not for a while.

JvG

The maf has a wire in it. One just sprays the wire.
there will be instructions on the web also YT videos.
search heading 1995 -99 maxima maf clean or similar. There is no need to wear a respirator.

you will just be spaying the wire for a second at most.
no diiffent than deodorant or spraying a bug.

do you have auto trans of 5 speed.
I learned to downshift when I started driving when I was 17. I lived in an area with steep hills and canyons. At high altitude.

The transmissions and engines are specifically designed so that they can be downshifted. Remove your foot from the gas pedal while shifting of course.
Downshift one gear at a time till you get used to what happens. If you have a manual transmission release the clutch pedal slower than normal when downshifting.

Evidently no one has taught you about shifting to cope with hills. So experiment. You will be doing what you should have done years ago.
All will be ok as long as tge engine stays under redline.

90sWheels

My Max is automatic. It's surprising to learn how fast it goes in only 2nd gear. I thought it was 4 gears and then OD gives you a 5th. However, I remember reading something about 3 gears and then like a 3.5 gear thing where you get direct connection, before OD

I wish I had a standard, as I don't do much stop-and-go city driving. Also occasional bouts of "spirited driving" are much more satisfying on stick, I'm sure (better for the vehicle too). I drove 1990-era, small, under-powered Japanese trucks for a couple stints - not exactly the Corvette experience

The one time I had the needle in the redline was when I tried flooring it from a stand still, and the transmission slipped! It was a whole lot of sound and fury, signifying car abuse and idiocy Hopefully no serious damage was incurred.

JvG

So now you are downshifting some.
Yes, doing that does help acceleration when you need it. Also helps control decent down a hill.
Especially in rain. I'm familiar with your driving conditions. I live in Portland.

I mentioned how my accelerator stuck open on thr freeway. It was right at a major junction with a belt route freeway. No place pull over. Big truck behind me.
I had to depressive clutch. RPM over 7000 for a minute or two. No harm done

90sWheels

That must have been quite something! At least on a manual that reflex to disengage the transmission comes more naturally. There is this story of a woman named Anne Hech - some actress - who died under mysterious circumstances not too long ago. There is video of her car speeding at about 90mph through a residential neighborhood... with the sound of brakes screeching. After they pulled her out of the wreckage there is more video, this time of her sitting up in the stretcher like "I'm okay, where are you taking me?" Some people say internal injuries don't take effect immediately, others say that, well, it was a hit. All I can say is I like driving my car that has limited amounts of computerization. And with that damn bubble shape they make every car these days, the A-pillar gets in the way of visibility.

Long Live Max!

90sWheels

By the way, @JvG , I was glad to hear that the unintended revving of your engine was due to a screw poking out somewhere and not AI gone awry

Today I got my knock sensor changed. With my medium-sized hands it was a challenge, but doable. At first I mistakenly thought that the screw was in the right place and kept trying to thread it, to no avail. Once it was actually in the right place it was easy as pie. Without gloves there would have been blood loss. I went for a little drive and it did seem like the low-end power had increased a bit, which is what I wanted. I can't wait to fill it up with Premium
https://invidious.fdn.fr/watch?v=Tp8INMugpf0

JvG

You should notice an increase in performance and perhaps mileage once you fill with premium.

it's most noticeable when accelerating at highway speeds.

90sWheels

That's interesting, thanks, I'll have to look out for that. I thought my low-end power was better but it's hard to tell. Also maybe it sounds a tad more growly.

90sWheels

Alright here's my update.

Gas mileage was 25.2 combined when filled with Premium and KS installed. Maybe more oomf, enjoying it

The hooting noise turned out to not be an owl stuck in the dash, as another flush of the steering fluid reservoir sorted it out.


Other little questions that I have:

1) The molding around the rear windshield needs some glue or something to hold it down at the bottom corners - any recommendations on product? Gorilla Glue, Duco Cement, "Silicone"? I have taken it apart one time no problem, just didn't glue it.

2) The wiper arm is hitting the back edge of the hood, causing a paint chip and clunking noise. I believe my parents had the windshield replaced one time and maybe the wiper motors. If I take the cap off the wiper arm will I be able to adjust the resting position of the arm, or is there something out of alignment here?

Turbobink

iTrader: (2)

This is just me, but for the rear glass trim, I’d use a urethane auto glass adhesive. If this is what you’re wanting, it’s available at pretty much every auto parts retailer.

Your wiper arm is easily adjusted by lifting the cap, removing the hold-down nut, pulling the arm off the toothed shaft and just repositioning the arm to a proper range of movement.

90sWheels

Thanks, Turbobink, you are a scholar and a gentleman

Turbobink

iTrader: (2)

Welp … I’m typically associated with terms like persnickety, ****-retentive and a**hole, but thanks all the same.