Thread: HELP weird idling/dying issue

So, just got my p11 turbo working again after 5 months of being down cause of transmission issues/being laid off with no money to fix it. I went to start my car and everything is perfect except this weird issue of my car idling and dying. The car warms up like it should, perfect idle no problems, but when it's warmed up(after about 10mins) or driven around it has idling issues to the point where the rpms would drop down to 500-600 then back up to normal idle to 1200rpms then sometimes drop and die. The car drives perfect and no bucking or what not. The weird thing is, if I were to press the brake pedal, turn on my headlights, fans kick on, or turn on the air(heat or air conditioning) the car idles perfect(850-900rpms) and doesn't have erratic idling and won't die on its own. Now, I only have to do one of those things mentioned to stop the car from erratic idling and/or dying which is weird. I expected a vacuum leak or loosened t-bolt clamp from the intercooler pipes somewhere, but all is checked out. I also noticed, when I don't rev or do one of those things above, My fuel pump(walbro 255hp) sounds a little louder than it should be until I press the brake pedal down or turn on the air, but the fuel pressure doesn't change or hasn't changed. I also monitored my wideband and when the erratic idling happens, it fluctuates from 13.1 to 15.7. I don't know if it's the ecu? Maybe its been awhile and the battery has been disconnected or something and its doing "the learning process?" Or because the car has been sitting for awhile and needs to be driven around a little more? I don't know, but honestly I do remember it did the same thing before my transmission blew, but not all the time. Only about 2-3 times a month and it didn't really bother me. It did the same thing for the past 2 years before my trans blew. But now, starting and driving it for the first time, it's doing it non stop. It doesn't really affect me when driving around since I press the brake in at stops, but it's kinda annoying me now.

I'm having a similar problem....mine idles fine til it warms up then cuts off,but if driven it runs fine,though when coming to a stop it fluctuates in rpm then drops below 800rpm and wideband reads 10.8-11.2 afr...nistune is reading a bad maf code.Ive switched out the mafs(n62)and same similar problems...next thing I'm going to do is rewire my pigtail and ground to chassis instead of intake manifold

I also checked the maf wiring to make sure I didn't bump it or something putting the trans back and I have one of the ground wires from the n62 to the chassis and the other to the stock ground wire from the de maf, I even put both ground together and really didn't make a difference at all.

maybe check your battery to ground connection and engine to ground

i did notice the ground cable on the battery was tighten down, but then after I did that, it was still doing the same thing.

CTS

Verify that the negative cable is going from battery -> frame -> Engine. Verify that that there is no excessive resistance with a DVOM.

What Duty Cycle is your AAC/IACV running at?

Also test for vac leaks

I have a JWT tune for an ECU, but I was wondering how would I check my duty cycle for my AAC/IACV? Before I did my engine swap I change every possible sensor on the engine especially that part since it was already acting up on my N/A DE. Also for the CTS, that was my culprit with some idle issues I had before with my N/A and I changed that sensor before my swap since its a PITA to get to, but then changed it again last year since I just like to change small things every year. I also read something about the walbro fuel pump that when it whines very loud its about to give up and noticed when I don't hear it whine so loud during idling or driving on the highways, the car idles fine. And the whine has been loud a couple times in the past and I would have some idling issues. But I will go through some more ground possibilities and clean/change some ground points on the engine later, also just double check for some vac leaks and give you guys an update especially to some who is experiencing the same problems.

Scan tool, Techtom, Consult, Etc... If it was already an issue and you replaced it, then you may have a wiring issue or it may be mis-adjusted. Once again, the need for a scan tool.



A fuel pressure gauge will help you determine this and on a turbo car is highly recommended. Personally I am not a fan of the Walbro and prefer the Z32 pump which is made by Bosch.



Smoke test is your friend for finding Vac leaks...