Did everything I could from what everyone else experience and still nothing.


Installed 5th gen IACV in my 00vi. I wanted to try the 5th to clean up the engine bay. Everything went fine at first, it idled high and slowly lowered itself to 850rpm~. I wasnt happy with it being that high seeing as others have a perfect 650-700 idle with the same setup so I attempted a "IACV re-learn" from the 00 FSM. Did the whole warm up car, unplug brown TPS plug and reconnect within 5 seconds, etc....


Then it started acting funny. Idle was high and it was reving itself! It would rev from 1500 to 2000 back and forth about 5 times and then settle back to ~1000rpms. Now when I drive, it shuts off on me if i let go of the gas, i have to constantly keep it at 1000rpm or it will just dip and turn off the engine.

Also, as soon as i start it, the RPM needle jumps like it normally would at cold start, but now it seems to hit a wall at 1000rpm. Like the ECU wont let it idle higher on cold starts. Then it starts reving itself slowly to 2000~ rpm and back down.

Any ideas on this Haunted idle? Only thing i did to IACV was clean it with some diluted degreaser.

 

Check your plug. Mine would rev it self like that when the plug wasnt all the way in or if it was upside down. As far as the stalling issue I just adjusted the throttle cables. My 00vi doesnt stall any more but the 3.5 does sometimes.

 

I tried my best to understand the pioneer of the "chopped plug" for the a33 IACV, my purple and yellow wire are on top, as in, facing the air box. Is that correct? Im thinking the pins might not be sat correctly, even though the chopped-plug would sit in all way and not bend the pins when removed to inspect fitment.


thanks aj.

I reset the ECU again and it seems to idle at 750 fine...but i usually takes couple miles for the ECU to realize wtf is going on and start retarding things. Gotta take my girl home...crossing my fingers.

 

I ended up getting a steady idle now. I opened up the butterfly plate more using the stop screw on the throttle body and reset the ECU. Doing the re-learn procedure didnt help when adjusting the TB stop screw, i had to reset the ECU in order for it to adjust itself to the new settings.


Anyways, now i got another problem. Now when im driving, there seems to be a lag between 2k-2.5k rpm when the tranny shifts. As if there is no power in that range and it takes more pedal just to get it to 3k.

Say I gradually step on the gas up to 40% throttle from a dead stop. It will stay in first and once it reaches 3.5k rpm, it will shift into second and the rpm will drop to below 2.5krpm, and it will lag.

Could this be a a side affect of adjusting the TB or a tranny symptom?

 

2000 idle re-learn on a 1999? Do 4th gens actually have a idle relearn procedure?
The high idle is normal as far as I can tell with a 00VI on a 4th gen. Mine is above 700 and I used the stopper screw on the TB to get it to that. If I pull the stop screw back out, my rpm drop to much when coming out of gear and stall. I might try the ECU diagnostic screw to compensate and lower it.
As for the dead spot, I have the same thing, lower rpm range, but I attributed that to the **** engine.

 

thanks dave, you're right. 99's procedure isnt like 2000's. I was under the impression the IACV was in charge of the re-learn, not the ECU. What was your adjustment procedure like with the TB screw? Did you have to reset the ecu any time after a adjustment? Mine idles fine after its warm, 750, but im assuming the ECU is taking over at that point and compensating for whatever crap position the TB plate is in. At cold start, it idles at about 1100 for 5 minutes and lowers until i start driving.


I just did a test run for every gear, seems to be JUST 2.5k RPM. When i put the shifter in first and gradually pressed the pedal, it always seemed to lag at 2.5k rpm, once it reached 3k, it started making power. Same for 2nd.

Only thing I did during the IACV install was rtv the rear valve cover... (which STILL LEAKS!!!) and add a bit of auto transmission fluid to the trans because of a leaking axle seal. I didn't add much, about 1-2 ounces to compensate what it was dripping since my passenger axle was replaced a month ago.

I probably shouldn't have added seeing the dipstick read above the high level before. I just assumed it was another ****ty dipstick design by Nissan, and couldn't have possible had so much fluid in there if its been dripping.

Anyways, I doubt its the transmission, it locks up fine and shifts fine. Its just 2.5k rpm that seems to lose power. (can the transmission slip even after its locked?) I'm going to attempt to re-seal the rear valve cover for the 4th time and make sure I dont have vacuum leaks in any of my gaskets.

 

bump. Removed everything, checked for vacuum leaks, everything seems clean.

Dave, are you also using a 5th gen IACV? I might just put up with having a mess in the engine bay and put back my 4th gen IACV, at least it performed better...





edit: Even after opening the TB plate with the screw, which seemed like a lot, i got the car to start if i hold the gas for couple of seconds. It doesnt idle normally like a normal cold car would (1300~rpm), it just starts, jumps to 1100rpm, and falls right back down to 800 and lowers itself to 700.

Also, I've tried doing idle adjustment with the TPS off and warm engine, but the car idles at ~+2000rpm's, even with the TB fully closed with the stop screw pulled all the way back. I'm not getting any codes except for rear o2 i deleted. Is there a way to test if the 5th gen IACV is working? Such as ohm readings?

 

yeah, 5th gen.
My IACV is weird though. It works fine but if I move the TPS or IACV wires, the rpm jump and it sucks in air. You're problems aren't IACV related, I don' think. Did you check voltages at ecu harness?

 

If your car is starting and holding a reasonable idle then your good. I wouldnt worry about it. I've been through all of that and I came to the conclusion that my car will do what it wants lol. But its running normal as of right now. I start it and it idles high then gradually falls to around 730ish. Im sure the next time I start its going to do something retarted just because I wrote this.

 

5th gen IACV wasnt working out for me. Harness continuity checked out fine, IACV's checked out fine (ohms). Maybe it was because I 'running coolant or not compatible with a 99 ECU, i dont know for sure.

I switched back to 4th gen IACV and set the TB close to stock settings using a untouched 5th gen TB i have laying around. Car started right up just like it used to. Never dips at stops and warms up normally.


Thanks for the help guys.