Hey there everyone, old time member that hasn't been around for a few years and couldn't remember any of my info...

Anywho, here is my issue... I have a 2001 Infiniti G20 Automatic, has an SR20DE. I picked it up with a CEL p0505 for the IACV-AAC. I gave it a tune up with NGK wires/plugs, cap, and rotor hoping it would help the idle out as well, and changed out the IACV for a new one. Nothing...

The car will start up somewhat low idle, at times almost stumbling and stalling out, but no more than 5 seconds after COLD START, idle skyrockets up to about 3000 rpms. I've tweaked around with it and gotten the idle down to around 1500 rpms at times then it will go up to 2000, and everytime even without touching anything it will decide to idle differently.

I have gone through the FSM for the IACV and everything shows it is working as it should. I then moved on to the TPS and found the voltage readings were off SLIGHTLY not enough to cause the idle to go crazy. At this point I brought the car down to a friends shop and hooked it up to his new Snap On diagnostic computer....

Reading data I found the throttle closed position switch was faulty. So I replaced the TPS and set it... No change!... Super annoyed at this point I grabbed his smoke machine and ran smoke through the manifold and found no leaks from any vacuum lines or gaskets or anything like that. I have tried setting the idle with the Snap On machine and without it and it still will not come down. At this point I had a new MAF lying around so I threw that on, and it too changed nothing....

I have tried searching but to no avail I have found no fixes for my specific issue from what others have encountered. I will continue to search and see if someones solution will fix my problem as I want this car fixed.

If anyone has any information or insight, I would greatly appreciate it. Thanks in advance guys.

Reading your whole thread, I kept thinking "vacuum leaks", but I guess you checked that.

There's no obstructions or kinks in the line going to the IACV is there?

PapaSmurf2k3 wrote:Reading your whole thread, I kept thinking "vacuum leaks", but I guess you checked that.

There's no obstructions or kinks in the line going to the IACV is there?

Negative. I checked that and found it was clear. I did read about a knock sensor wiring issue. Now I did not mention I had a code for the KS as well... I did not think it would relate it any way shape or form... however i think it may. The only two codes I had were the iacv and the ks...

Upon reading another thread I saw there was issues with the shielding of the KS sensor wire grounding out and causing a short... I looked into the wiring some more and found that the iacv wiring was showing continuity in one another at both the plug and the ecu. I found continuity between other wires as well leading me to believe that there is a short somewhere...

I decided to depin the iacv plug and the wires for it at the ecu and with some extra wrecked harnesses I made a direct harness... by doing this I believe I have eliminated the ecu as a culprit due to two reasons...

First when hooked up to the diagnostic software it shows the iacv output... second with the iacv direct with my sub harness the code is gone....

Now with that said the idle is unchanged... the iacv does not make any noise prior to KOER as stated it should in the FSM... mind you the iacv is brand new but I'm thinking that it may have shorted to fault.

I don't remember off the top of my head but is the iacv always open and controlled to close or always closed and controlled to open?

Now with this subharness the iacv code is gone as I stated... but now low and behold I have a new code, because what would diagnosing be if it were easy and you solve one problem, you solve em all.... code for MAF sensor popped up now...

pisses me off because without going through the flow chart and just seeing the voltage on the diagnostic software it is within range..... at 2500 since I can not get the idle to drop...

Only thing i have done to see the outcome is I've pulled the vacuum line on the diaphragm that pushes the throttle slightly and taped up the iacv opening on the filter side and it idles pretty well... however obviously is not the right way to get this idle down :p

Any ideas? I'm leaning towards a shorted engine harness, possibly from the damn power steering fluid leak on this pos...

Is the engine harness standalone to the ecu? I didnt notice any plugs to disconnect it at the firewall so I'm guessing so and what a b**** it will be to pull out.

BTW sorry for the long posts. Trying to be as detailed as I possibly can to get the best possible assistance one can give over the internet and not diagnosing it them self.

Yeah its one bigass harness, although you MIGHT be able to cut the beast at the fuse box.

Have you tried unplugging the MAF completely?

PapaSmurf2k3 wrote:Yeah its one bigass harness, although you MIGHT be able to cut the beast at the fuse box.

Have you tried unplugging the MAF completely?

Yes, with no maf it acts very weird.