Hey all, still working some of the bugs out of this car. It's an '86 with a 350 TPI from a 1990 and a T-5. One of my biggest problem is the erratic idle. Sometimes it will idle at 2200, sometimes at 1000-1200, and sometimes it just conks out. Engine and ambient temp seem to have little effect on how the car chooses to idle. I think the chip that is in it is a hypertech meant for a 305 tpi from an '86. Could this be causing my problem? The car runs great other wise..... good power, never runs hot, good oil pressure. I checked the wires..... the all look good and the car doesn't sound like it has a mis. I also check the vacuum lines and don't seem to have problem there. I checked by shutting the car off and hitting the brakes after about 15-20 mins. Still had brake assist.

Any ideas... or at least a starting point?

 

Anyone?

 

Dunno, but mine ha developed this too, idles fine, drop into drive & it just quits.
Checked everything, all 'seems' ok, at my wits end.

 

Is the fuel pressure changing? I had a stalling problem that was caused by a Holley AFPR with a leaking diaphragm.

About the PROM, a 1986 car is a MAF intake, where as a 1990 is SD. The PROM's are not interchangeable. It's not clear in your post which system you are running now.

 

Heh... it's not clear on the car what I'm running either

Is there an easy way to check? I can't imagine it's fuel pressure because once she gets goin' it's smooth sailing. The car isn't missing and if anything smells as though it may be running at little rich. Also, not sure if this has anything to do with it but sometimes to start I need to goose the throttle a little bit.

Keep the ideas comin' please. I already had one get a ticket because of this. I was revving the motor at a light to keep it running... guess he thought I wanted to race, too bad he didn't see the cop sitting right behind him

 

if your running an 86 prom with a 1990 engine, thats your problem. You are going to HAVE to change the ECM and PROM to at least a 1990 system. The Engine Control Management systems are not interchangable as stated eariler in another post. You trying to run a Mass Air Flow computer system with a Speed Density(No M.A.F.) Engine system.

 

I'm not sure what all is in this car.... just got it a week or so ago. Is there anything I can look at that will let me know? A part number or something? Also how can I tell (by looking at the engine) whether or not it's speed density or MAF?

 

Ok, here's an update. I think I found my idling problem. The wires at the TPS are frayed and I think they were rubbing each other. Once I seperated them the problem got a whole lot better and I bet once I redo the wiring the problem will go away completely. Also, while I was at it I set the TPS:
I set it for 0.54v at idle and it was putting out 4.35v at WOT. Are these the correct settings?

Also looked at the ecm. Here are the two numbers on it:
Number: 7-7165
DC Code: 0404mt

Looks like an newer ECM. It was dated 2005.
I think I have a MAF on this engine. Is this one:


I don't know what I got myself into with this car..... can anyone help me out?

 

Well you are holding up the mass airflow so that answers one of your questions. Did the wiring for the TPS help with with your idle? Does it still die out? Check your fuel pressure as well.

 

I ran into the same problem. Turns out i had a problem with the MAF along with the idle speed being off. The Chevy dealer reprogramed the idle speed afterwards and she has been a champ since.

 

Yeah, seperating the wires at the TPS helped a great deal. Is there any way to check a MAF sensor?
Also, any idea how to identify which ECM I have?