Sy Dies at Idle

[GAShan]

Once engine goes into closed loop engine dies at idle when in gear. Can keep it running by cracking the throttle. IAC counts slowly count down, truck dies when it hits 5,4,3. Stock trucks seem to idle with IAC in the 15-20 range. Replace IAC, checked all lines (Ian's kit) for leaks, disconnected one at a time and plugged, no difference. Truck runs great at any throttle opening including WOT.
Behavior indicates that air is getting in somewhere and IAC closing can't compensate. But wouldn't more air getting in make it idle faster not slower? Throttle blades look good, no crud. No crud in throttle body itself.
I haven't removed the cap and played with the throttle stop...yet. All other Diacom readings are normal.
Ideas?

 

[leroy]

Maybe an intake leak?

I wouldn't be scared to adjust the idle stop in the meanwhile.

Jim

 

[myclone]

Like was mentioned check for an intake or TB leak somewhere. FWIW when I put my upper intake to lower intake phenolic spacer on I found ALL the bolts barely more than finger tight. How it wasnt leaking puzzles me but it may be worth checking.

 

[V6 Kompressor]

Idle speed

Idle speed

Usually if the idle speed is too low, there is not enough air entering the engine. If I were you, try disconnecting the battery first for 2 minutes, then reconnect it and then start the engine and let it idle for 10 minutes. then shut it off for a minute, then restart it and let it idle for 5 minutes. This is the proceedure for 2.8/3.1 gm lumina's ,corsica's, grand prix ect.... to let the idle "relearn" it's set point. Here is another proceedure; With engine off, check for carbon build up on throttle blades, yes you have to remove IC to get to them. And clean the blades with rag and carb cleaner. If you don't wan't to do that, then with engine off, key off, jumper aldl pins A to B, then turn key on and listen for idle air valve motor run the pintle closed. When idle pintle motor stops running, unplug idle valve motor connector. Check to see if manual idle adjustment plug is still in throttle body, and if it is remove it. Start engine and set manual idle speed to 650 rpm. Then shut off engine , remove jumper, reconnect idle motor and try that. Some people have had to drive the car above 30 mph to reset it and some people have only had to unplug the battery for a couple of minutes without having to adjust anything.... I have the latest sy/ty, 93 prom that is supposed to have the unstable Idle thing fixed.... GM still has them in stock.... I would usually try the proceedure that requires the less money and time.... let us know which one works....

 

[TyMeUp]

Check that the Park/Neutral switch signal is seen by the ECM. (Watch Diacom dispay while you shift.)

This is a load signal that tells the ECM to increase IAC counts when in gear.
The other load signal is the A/C switch (or A/C clutch).

 

[Daron]

Re: Sy Dies at Idle

Whats your fuel pressure doing? Any possiblity the fuel pressure regulator could have bit the weenie? Run the truck, pull the vacuum line off of the regulator..
Also, consider trying another ecm..
Take care Gary.
Daron

 

[442typhoondude]

Im new on here and dont know much about the sy ty motors, but in my 93 jimmy (4.3 cpi piece of ****) i had the exact same problem(dies at idle, but runs good on the throttle). Do you have an egr delete. if not go check your egr valve. i replaced my injectors and mine still ran like crap. then it hit me to check the egr valve. sure enough a piece of carbon about the size of a large pain reliever fell out. If this is your problem get a delete or a filter screen. like i said though, im a retard when it comes to sy ty motors cause ive only seen one in real life once. so if im wrong, sorry.

 

[GAShan]

Thanks for all the input. Still not fixed. Diacom shows engine sees neutral/park switch. Dies when AC is turned on too. It appears that the computer in compensating for load. Cleaned IAC passage and entire throttle body. Didn't look bad though. Next step is to try another stock chip (piggybacked on the Ultimate) maybe that function went out. The try another ECM.

 

[ed hess]

fwiw i had two 7 page threadds about stalling last fall. we did everything you will read here. And i mean everything

when that motor came out i found the seal between the heads and lower intake was the cause....oh and it had been retorqed and 2x checked.

good luck

ed