97 Maxima SE 5 spd 284,000kms

Car starts great. When cold idles initally around 1,500 and then steadily drops to 750 as it warms up and holds steady there. Recently though, when I come to a stop, the RPMs remain at around 1,000 for a few seconds before dropping to 750. THey used to drop right away.

Also, when coasting (not decelerating) with little or no gas applied, the car will intermittently lurch when at 1,500 to 2,500 RPMs.

Recently removed and cleaned IACV (new gasket); cleaned throttle body (while attached to engine only- no gasket easily available here); replaced PCV; fuel filter; fuel pressure regulator.

Car runs smooth and accelerates strong with no performance problems.

Help!

 

Make sure your TPS is still within spec and that its secured properly. You might have loosened it or thrown it off spec while cleaning the TB. Should read 500ohms closed and 4k ohms at WOT. I had similar problems when I had a bad TPS. The engine would rev intermittently on its own.

Double check the IACV for any leaks at the gasket that you replaced.

Have you checked for any codes?

 

THanks. I'll check out the TPS tomorrow. No codes showing and haven't checked for ghost codes as I don't have a scanner.

I was thinking of taking the IACV back out and seeing if maybe something was not working properly. I gave it a thorough cleaning including taking out the individual pieces but maybe something is sticking.

Earlier today I did notice that the air temp sensor was not installed in the air intake. I installed it and the symptoms persisted. If it was just hanging in the engine compartment, could it have been damaged?

 

You don't need a scanner for 'ghost' codes. Not normally, anyway.

It's possible the IACV is malfunctioning, yes.

It's unlikely the IAT was damaged, but it shouldn't cause a surging idle issue.

 

Thanks.

I'll start with the IACV. Hopefully, that is it.

Would a plugged EGR tube cause this?

 

+1 on TPS, theyll often times wear out right at the cruising position seing as that is where it sits most times. Obviously if its a city car that sees little cruizing (think highway-light traffic) this might not be your problem.

 

I'll check the TPS while I'm mucking about in there. MOst of the miles on my girl have been highway. DOn't notice any problems coasting at highway speeds though only lower ones

I'm convinced the two symptoms are related as they both appeared at the same time.

 

Okay,

To the best of my knowlesge and ability, I tried to check out the TBS today.

Checking for continuity with the TB closed and open - there is continuity when the TB completely closed. THe continuity continues to be there until I insert a feeler gauge of .025. The Haynes manual says continuity should end at .016. Is this an issue?

Also with engine cold, resistance on TBS showed .78k closed and 3.9k fully opened throttle. (Manual says .5k and 4k, so not too far off). But...with engine hot, the opened throttle reading was still 3.9 but the closed throttle remeined in the 2.5 to 3.2 range and did not drop to .5. Is this normal? Problem? COuld this cause my lurching issue when coasting with no load.

Other info. I witnessed the fast idle cam appearing to function normally. The throttle lever was lifted slightly when cold and the lines on it and the Fast Idle Cam lined up. When warm, the throttle lever rested against the throttle screw.

 

UPDATE - TPS shows 5 volts from PCM which is normal.

TPS shows resistence of .8k closed to 3.9k open

WOT sensor was showing connectivity beyond the recommended .016 gap (.025) but today, I cannot get any connectivity between terminals 5/6 at all! ??. WTF??

 

UPDATE - TPS appears to be within spec. With engine warm it reads .58 closed and 3.9 open.

I tested the MAF and it also is within spec. Just to be safe, I had replaced it with a used one which also spec'd out and the symptoms remain.

The ATS and CTS both test within spec.

I adjusted the TPS so that the open/close sensor is within spec but no difference.

I recently replaced the PCV, fuel filter, plugs and FPR.

THe IACV appears to be functioning correctly. Increases revs slightly when power steering and/or air conditioning engaged.

THe symptoms only occur when the car is in motion coasting - not when accelerating - or while coming to a stop and for a few seconds after stoping, then the revs drop to 700.

Could it be the VSS? The speedometer operates properly but something is telling the engine to keep the revs up when it comes to a stop (for a few seconds) and while cruising.

EGR?

No codes thrown.

I'm running out of options here.

Oh...symptoms are worse when engine is cold and coasting at 1,500 in 2nd- lurches.

 

Check codes, 'ghost codes' are just codes that don't illuminate the SES light, you check them the same way as if the light were illuminated.

When it 'lurches', a little clarification:
- your cruising at 1500RPM, do the RPM's drop off (lower) then jump up OR- your crusiing at 1500RPM, the RPM's jump up (higher) then drop back to 1500RPM

And when it happens is it gradual... (slow/stedy shift in RPM) or does it kick up/down rapidly?

From your posts, it sounds like you need to just relax a bit, and then pop your hood, slowly and carefully go over the engine bay, look over and feel all wiring, connections, make sure everything looks ok, more times than not little things like this are due to us getting in there working on something, and forgetting a clip, or plug, or not noticing we rubbed a wire, never underestimate what the guy before you did, or what you may have done without knowing. You can scratch your head all day long over something silly so do this first.

 

Looks like you are a candidate for one of these!
http://cgi.ebay.com/ebaymotors/ws/eB...K%3AMEWAX%3AIT

If you don't have the $$ maybe a friend has one to hook your car to see via the ecu what it sees from the sensors. I just bought one to help me out with some coil pack issues under load. Replacing the CP's fixed my problem. But I realized I was just throwing parts at the problem. Without check codes, this car is hard to fix!! Too many potential high $$$ items that it could be. No affiliations with this brand. GL!!

 

THe tach does not move. The motion is aquick "jerk". Sometimes only once, sometimes a few. IT is intermittent.

I have been spending more time under the hood looking at thinkgs this past couple weeks than I have anything else. I'll keep poking around and checking things. It isn't a scarey problem as the car performs strong otherwise. I just tend to want to prevent things from getting worse. IT could be something the "Guy before me did" I had a clutch put in a couple of months ago and perhaps, they messes somethign up.

As it only happens when the car is moving and the tach doesn't register any variation, could it be tranny? I have a 5MT. The reason I thought engine is 'cause the symptom of revs being slow to drop when coming to a stop came about at the same time.

 

I definitely will be getting a scanner soon but for now, the car isn't throwing any codes and if it does, I have a mechanic here that wil scan the car for free.

 

are you sure it the engine that's causing the jerking and not the tranny?

 

Not sure (see my post above) Assumed it was engine related because of the slow-to-drop RPMs when coming to a stop but...the engine runs normally (including rpm drop) when the car is not in motion and runs perfectly other than this annoying intermittent "jerking" while coasting in 2nd and sometimes 3rd gear.

If tranny, any ideas on what could be wrong? I was wondering about the Vehicle Speed Sensor as this had been removed and replaced when the clutch was done. Maybe they damaged it? Speedo works fine though

 

If your sure the RPM's aren't moving when it 'jerks' then it's likely a tranny issue.

2nd and 3rd doesn't make sense though, depending on the exact symptoms.

Take 'er to a tranny shop and go out with the guy who's checking it, they usually check it for free.

If it's tranny related it's got nothing to do with sensors, not in a 5spd.

 

RPMs definitely do not drop or spike. It may be tranny related. I was thinking that as there are actually 2 symptoms, the one would be related to the other. THe high idle while coasting and for a few seconds after stopping I thought could be related to the lurching.

Exact symptoms are hard to describe though sometimes at highway speeds even when I let off the gas, after 2 seconds, it feels like the car suddenly brakes harder. Almost like the revs (or gas) is stuck a bit high for a couple of seconds? Is there a gas cutoff function when the foot is off the gas that could be malfunctioning?

I replaced the PCV with a non-OEM one a couple months back. If it is not a proper fit, could it cause the higher idle? I read here somewhere that the wrong PCV could affect idle speeds while coaasting or stopping.

I'd like to fix the idle problem and see if that fixes the lurching. It has to be cheaper than anything a tranny shop would want to do so is worth a try.

 

When I'm driving about 80 km/h (50 mph) as soon a I let off the gas the car jerks, slows down a lot and it feels like it shifts down (I have an auto). It makes it difficult to stay at 80 km/h. Sounds similar though, but the relationship is a little odd, if there is a relationship, since we have different transmissions.

 

Sounds a bit different than what I'm getting. My tranny and engine brake properly when I let off the gas but after a couple second delay. I believe this could be assoicated with my lurching problem because the same delay takes place when I come to a stop. Other than that, the car idles and performs flawlessly. It seems to me that for some reason, the engine RPMs are not dropping as low as they should when I let off the gas so that the engine is revving too high at cruising speed

 

Once again, take it to a good tranny shop, go out with the guy checking it so you make sure he experiences your complaint.
Sounds like it could be a clutch, you need to take the car to a tranny shop, free check will tell you where to look, otherwise we're just guessing on here.

 

I hear you. I just wanted to eliminate as much as possible before I take that step. Just had a new clutch put in 2 months ago so I hope that isn't the issue

 

if you had a shop do it it will be warranty repair, so I would personally hope that WAS the problem, if it's anything else you pay out of pocket.

 

Good point. I intend to take it to a tranny specialty shop first to hear what they think it is. If it is the clutch, then back to my indy guy to see what he will do.