When the car starts up it immediately goes up to about 2500-2700 rpms and then drops back down to 1800 rpms and just keeps going up and down between the two.

It started a couple of weeks ago when i pulled the '00 VI off to re-route the part of the wiring harness for the IACV and to tidy up a few other things in the engine bay. I reinstalled the '00 VI and thats when the car started idling retarded. I figured i had a pretty bad vacuum leak since i over-torque'd a couple of the bolt for the upper intake manifold. I went ahead and converted everything back over to use the USIM so that I can sell the '00 VI. I've got everything installed just the way it was before but I just can't figure out this idle problem. Anyone else got any ideas?

 

oh and here is the intake manifold i'm using if it makes a difference...just a slightly modified stock piece.
http://forums.maxima.org/showthread.php?t=365446

 

Sounds like an IACV issue, I know a buddy of mine's honda would do that when his IACV went bad. It could also be a TPS issue (as far as the "idle" range,) but I doubt you unbolted that durring the swap, and I don't believe it would cause the irradic/fluctuating idle like that. Also, did you make sure you're throttle cables we're loose enough to let the TB close all the way? Not sure of bracket location on the 00vi in relation to stock/mevi, but that could be part of the high "low end" of the rpm rise/fall.

 

yea i'm going to try a spare IACV tomorrow that I know is good for sure. the adjustment on the TPS can't get any better. I messed with that earlier. and since i'm back to the stock USIM the throttle bracket is back to its original spot.

 

this sounds like IACV to me too, people often have this type of issue with a 00VI swap and its often the IACV.

 

that happened when i put my CAI on my old 95 accord, i disconnected the battery and put it back and it was fine. " just a thought"

 

alright, anybody want any parts before i put a rag in the gas tank and light it?

 

also noticed the tach doesn't really move. it just kinda bounce between 1500-2000 rpms and doesn't even go above 2000 when i rev it up? anyone at all got any ideas?

 

anything thats free is mine......

 

nice try but no dice. if i can't get any help then the car will just sit there.



maybe i'll get more help in the 4th gen forum...

 

is the MAF plugged in?

 

yep. i've even swapped it out with another good one. still can't figure this **** out..

 

It's either a IACV problem or a vacuum leak. My money's on the vacuum leak.

 

^^ +1. Have you tried spraying BPC on and around the manifold?

 

IACV is fine. already tried swapping it out with a good one. I bought a NEW intake manifold gasket today. these things are much cheaper than i remember them being. i'll probably try it again tomorrow.

and whats BPC? i'm not up to date on my abbreviations.

 

Brake parts cleaner...

 

i've tried it around where the throttle body bolts too and the front side of the intake manifold but didn't notice it doing much of anything.

 

Are you sure you don't have a hose loose? Maybe a disconnected PCV valve? Do you hear a hissing sound?

 

not sure. its been a couple of days since i messed with it. i'll check for the hissing sound tomorrow.

 

where the leak is I'm sure too sure but it is a leak somewhere. My car did the same thing till I found the leak and plugged it. My leak was in my Pathy TB. My idle was 2.4K-3K back down and up, after i plugged it. idle was 660 period.

keep searching the leak is somewhere.

 

where at in your pathy tb was the leak? i'm also running the same TB but on my stock intake manifold.

 

just pulled took it all apart and did it all over. still no luck. anybody got a lighter?

 

my pathy TB was leaking at the bottom of it. I did not make a block off plate and that threw my idle waay off. From the link you posted above I saw you already made a block off plate, so pretty sure that is not the source.

 

i noticed some moisture around the edges of the block off plate when i pulled the '00 VI off. so i used some black silicone and sealed it up. The car does have a VAFC-II on it and the wiring isn't the greatest job ever but is much better than anything i would've done. I'm thinking it might be something with the wiring. I hate wiring.

 

buuuuuuuuump.


just decided to mess with the car again tonight. uninstalled the VAFC-II and soldered everything that needed to be soldered back together. I noticed the vacuum line for the FPR wasn't hooked up so i did that. I charged the battery and started it up.

I STILL got the same damn thing going on. The tach jumps around a little between 1700 and 1900 rpms but the car is definitely revving higher than that. Any ideas?

 

Grab a can of carb or brake clean, put the straw on it. Then start the car and start spraying the can (in short bursts) towards possible leaks. The engine will tell you when you've hit the 'spot'.

 

just tried that and nothing happened. I checked any and everything I could think of.

I had no CEL but I decided to check the codes anyway and got 0201 - Ignition Signal Circuit code.

Any ideas now?

 

I would've banked on the TPS, but since you said everything is good, I would check all the spots around the IACV harness, maybe a contact came loose? You have a PTB?...I would check that (adapter plate etc..), alot of people I know had bad leaks and sealed em up and the idle was perfect, I'm just stuck with the cold starts..

 

TPS is showing proper voltage with the throttle body closed and open. I unplugged all the harnesses for the IACV while the car was running and nothing changed so i plugged them back in and still the erratic idle. After I did that though I cut the car off. I let it sit for a minute then started it back up and the RPMs just started slowly rising like the TPS was unplugged. I unplugged it and plugged it back in and it went back to the erratic idle. Could that mean my TPS is bad? I assumed it wouldn't show the correct voltage with the TB closed and when opened when tested with a multimeter.

I don't have an adapter plate for the PF TB. I'm running a slightly modified stock Intake Manifold; see here. I've got a gasket i made out of gasket material between the TB and where it bolts to the neck of the manifold.

 

DTC 21 (P1320)

Malfunction detected when:

The ignition signal in the primary circuit is not entered during engine cranking or running.

Check item (Possible Cause)

1. Harness or connectors (The ignition primary circuit is open or shorted.)
2. Power transistor unit built into ignition coil
3. Condenser
4. Crankshaft position sensor (REF)
5. Crankshaft position sensor (REF) circuit


Taken from the 95 FSM

 

that wouldn't be the cause of the erratic idle though would it?

 

Possibly. The CPS (REF) is the sensor that tells the ECU where the #1 piston is at in its stroke and all the ECU's ignition timing calculations are based off of it. If that sensor is bad it could screw with the timing.

Which coils are you using?

 

i'm using stock 4th gen coils. I think I have some spare ones sitting around i might try and swap them out. anyway to test the CPS (REF) sensor?

 

Visually inspect the sensor for chipping, Resistance @ 68*F= 470-570 Ohms. Also, check the ground circuit for it, one of the grounds for the ref cps is one of the two manifold grounds..........

 

when you say to check the sensor for chipping you are referring to the CPS sensors right? I'll be checking all this stuff tomorrow since it should be a little bit warmer out.

 

sensor and pulley.

 

Any updates?

 

Yep, I got tired of troubleshooting the problem so I just took it up to a Nissan mechanic and he is gonna check it out on the side for me.