dibquib

Just replaced my TPS at 300,000 kms. I adjusted the Open/close sensor for continuity as per Haynes instructions and checked the TPS getting resistance of .65 at closed and 4.45 at wide open.

Started up the car and the engine now idles at over 2K RPM! If I disconnect the TPS it drops to just over 1K. I adjusted the IACV with the TPS disconnected down to 750 but when I plug in the TPS it races back up to 2K.

Help!!!

Coolsaber57

iTrader: (22)

Check for Vac leaks.

dibquib

I have been playing with adjusting the idle and it appears to be close to operating correctly except...when I coast to a stop, the RPMs rise to about 1100 and stay there until after I stop moving for a couple of seconds and then drop to 750 and stay there. If I am just sitting still idling, it returns right to 750 after revving up the engine.

Could this symptom be caused by something like the speed sensor? Vacuum leak? Anything else?

The good news is, I replaced the TPS in the hope it was bad and causing a lurching/bucking while at coasting speeds. This problem appears to have gone away completely. Only the slow idle drop after coming to a stop remains.

dibquib

UPdate - Idle is good, smooth and stable. Lurching and bucking are gone.

Slow dropping idle symptom remains. While coasting to a stop (clutch in), the car RPMs drop only to 1200 and for about 4 seconds after stopping and then it drops to 750 and is stable. If I coast with the clutch pedal out, the RPMS will drop lower but rise to 1200 as soon as I push the clutch in. Even while coasting down the road, if I push in the clutch, the RPMs only drop to 1200 and stay there until after the car comes to a stop when, after 4 seconds, the RPMs drop to 750.
This appears to be tied to vehicle speed. I've cleaned the TB and IACV and replaced the gaskets.
Anyone got some thoughts??!

dibquib

BUMP

Replacing the TBS solved my lurching problem but slow idle drop still an issue. ALl vacuum hoses appear good and it runs and idles smooth except for the slow to drop idle problem.

IN adjusting the IACV to get a solid 700 RPM at idle, I had to turn the adjusting screw all the way in. RPM is now 700 without AC on and about 900 with it on.

MAP??? IACV???

JNCoRacer

iTrader: (6)

No CEL?

dibquib

Well, initially there wasn't but just recvently it did come on. I had the local guy scan it and he found a P0110 code which he says is the Air temp sensor circuit 1.

He was pretty sure this would not cause the idle drop problem though.

JNCoRacer

iTrader: (6)

And youre sure everythings plugged in all the way? Everything around the IACV, TPS?

dibquib

I've inspected around there dozens of times and found nothing loose or worn looking. I cleaned the IACV a while back and replaced the gasket. same for the TB.

The CTS tested within spec and the car idle drops as it warms up as it should. THe high idle problem only is exhibited when the car is coasting (clutch pedal in) and for about 3-5 seconds after coming to a stop.

Could the fact I had to screw the idle adjusting screw in all the way mean the IACV is letting in too much air? i.e. the plunger is weak or not closing all the way?

smai555

check the flux capacitor.....

have you checked the cold idle to make sure it is working correctly?

dibquib

I think so.

THere is about a 3mm gap on the idle set screw when the engine is cold. WHen the engine warms up there is no gap at all. I believe that indicates the cold idle mechanismis working correctly.

JNCoRacer

iTrader: (6)

And your throttle cable isnt too tight is it?

dibquib

Nope. Made sure to leave lots of slack there. throttle assembly seems to move freely and return to full close after revin up.

dibquib

Checked Air intake sensor and sure enough, it wa not plugged all the way (not clicked in). Drove around but no change in symptoms. I'd be sure of the IACV except when the car hasn't been moving, everything works perfectly. If it was a vacuum leak, would it not have the high idle symptoms all the time? I'm stumped.

Q8BallMAXIMA

I had a similar situation, but it was my fault. I took my TB off to clean it and I didn't replace the gasket and it did the same with the rpms only that the rpms didn't drop back down....I had a leak between the TB and air intake.

Fixed everything, Now I have the idle situation you have to this day.

dibquib

Well...I know I replaced the gasket I may do some more spraying TB cleaner around to see if I get some idle fluctuation but I have tried that to no avail. Maybe the IACV is going (no code though) or the Coolant temperature sensor. Starting to get a bit frustrated

Q8BallMAXIMA

I did notice I had a little daylight showing through the butterfly on the top and bottom after cleaning the TB. It may have something to do with the idle situation yet...but I am going to live with it....it still hasn't caused any CEL yet.....it has been about 2 months since cleaning.

cefiro a32

I am having the same problem with high idle after changing TPS. I warmed up the car before adjusting the TPS and the idle was fine. However, after i adjusted the TPS to about 550 ohms at closed throttle and 3900 ohms at WOT the rpms went up to around 1700. Before i adjusted the TPS it was reading 300 ohms at closed throttle.

ebadai98

iTrader: (2)

i am having the same problem while driving sometimes with my foot on the brake in drive the car idles at 1k and when i place the car into park it reves up to 2k i don't know what to do.

aackshun

iTrader: (3)

Mine does the idle thing too, and this all happened after a TB/IACV servicing, but my friends (who don't own maximas) says it's normal but I don't recall my car doing it before hand...

Does it rev up to 2k then back down over and over again? If so that's the sign of a bad IACV, even though I rarely hear about those goin bad on 4th gens.

defiance

iTrader: (1)

I guess these are GOOD symptoms guys as most of you have clean TB and IACV's and there just letting more air in compared to the dirty ones...

I did notice a high idle after i clean both my TB and IACV as well but i Just live with it don't think anything come be done for it.

cashoit

Honestly, it sounds like the TB and or IACV arent sealing correctly when closed.

cashoit

Let me ask this tho.....when u start up the car does it idle at around 1500 rpms??? Mine does until the car is warm then it goes down to normal. Both maximas i have owned had this issue.

ebadai98

iTrader: (2)

yea mine does that but like you said that's normal when the engine is cold. I just cant figure out why its at 2 when the car is placed in park it doesnt do it all the time just sometimes i just don't want it to hurt the engine and have a problem stemming from that later down the road.

dibquib

SOrry to bump an old thread but...

THe symptom of temporaty high idle persists and is driving me crazy!

The car idles correctly when stationary (cold and hot). While stationary, if i rev the engine (warm) the RPMs drop smoothly to about 700. The problem is, when I am driving around and come to a stop, the RPMs drop only to 1K or so for about 3-5 seconds befoe dropping to 700.

I have cleaned the TB, MAF etc. Replaced the IACV; TPS; ECS.

Could this be caused by the speed sensor somehow telling the PCM that the car is still moving? Camshaft sensor? O2 Sensors? KPS?

The car never did this in the past so it is not "normal". I have almost 200K miles on the engine. NO signs of any vacuum leaks.

buttonhook

iTrader: (4)

Mine does that too. Im and auto but in drive and coming to a complete stop it will hold at like 1000 rpms for a few seconds before droping to around 700. I dont know wht to tell you.

cashoit

SOunds like ur IACV is sticking momentarily. Check CPS, TPS, CKPS (POS) per FSM. COuld have a loose or corroded wire for TPS or IACV. U clean IACV tube going to engine? Throw some chevron in the tank lately?

EDIT:

Its almost as if the car takes awhile to detect Closed throttle. THere is a thread onn here where someone replace the TPS and they had to complete this trick procedure to get the car to idle right. Forget who it was tho. Do a SEARCH. Also look in Haynes for ideas too.

dibquib

That's what I thougth but it only happens after coming to a stop not when the car has been stationary. THat's why I was thinking maybe the speed sensor or something else?

I replaced the IACV gasket and when that didn't work replaced the whole thing...no change. WHIch "tube" are you referring to? The opening wherer the IACV goes? that I cleaned thoroughly.

I'll see if I can find the thread you refer to. Still...it idles like a charm except for the coming to a stop issue.
Misery loves company. Hopefully this can be resolved for both our sakes.

cashoit

check ground for IACV and TPS. Might wanna run new wire for the leads. Either that or the IACV is sticking. But u say its new. Leads me to think TPS or IACV. U have an air issue.

dibquib

Wires all appear in good shape. Not actually a new problem. Was happening before I switched in new TPS IACV MAF and CTS.

The weird thing is that everything related to the idle (cold and hot) runs normal with the exception of the idle drop when coming to a stop. If it was the TPS or IACV, electrical or air leak, would the symptoms not always be there? Makes me think of something related to how the car operates in motion versus at a stand still but I don't know what that could be. THat's why I was thinking speed sensor.

dibquib

Here's another clue...

When driving even at highway speeds, if I depress the clutch, the RPMs drop to around 1K but will stay there until after I come to a full stop for a few seconds before dropping to 700.???

JwaxMax99

iTrader: (14)

Did you correctly set the TPS.? Using the feeler gauge?
My car acted the same as the above posts, till I set TPS.

dibquib

Yeah, It was a fussy job but I got it set according to spec.

I had this problem before I chaned out the TPS too so I'm pretty sure it isn't that.

cashoit

Change PCV?

Maybe a vacuum leak too. NAw if it was a leak, the car would exhibt symptoms all the time.

Is there free play in TB and IACV? Like, they both actuate freely and smoothly.

Honestly, it almost sounds electrical to me. hmmmm,(thinkin out loud here), take foot off acceleeraotr, TPS closes, ECU sends siganl to IACV to actuate, ECU modulates air via CKPS POS which sensens engine speed. VSS sends speed to speedo, speedo sends signal to ECU. VSS works with CKPS, CPS, TPS to determine fuel delivery.

If IACV and TPS actuating freely, check CKPS POS, and VSS. Check grounds and remove the sensors to see if they fouled.

EDIT:

See the problem is that for the most part, the car running fine. U jus have a slight glich, Those the hardest to diagnose.

dibquib

I agree totally!! It is annoying but the car runs strong and smooth. Frustrating!

OC_Nooby

iTrader: (11)

Sorry to bump this thread, I'm experiencing the same issue on a 5-speed. Although mine will stay at 2k if say I was to drive the car at 2.5k rpm then put the clutch in the rpm's would drop to 2k, hover for a while then drop down to normal. Only happens when warm. Its driving me nuts.

OC_Nooby

iTrader: (11)

damn, going to try an IACV...The thing is people with 5gens are having the same issue as 4th gens. So it might not be the IACV...

rzyjtw

When I put my maxima 97 in reverse, the engine begins to accelerate and decelerate. What could cause this? .. It may be the TPS?

Phromethius

This thread is 2 years old? Also your description doesn't make a lot of sense? are you refering to RPMs? If those are jumping search the forums for that. It could be ALL KINDS of stuff, from MAF to coils, to bad gas, to EVAP system. Search for RPM surge or drops and see if anyone else has posted something similar to your experience.

As it was stated in the stickies from Kevlo, these cars are 15 year old cars. There is not many "new" issues that are popping up.

Once you find the right issue the Org can help you but try to narrow it down a bit so we can get on your same page.

Edit: I had something similar when I first purchased my Max, it ended up being the Ignition Coils misfiring that was causing the RPM flutters. Just my experience thrown out there for you.