Intermittent start and stall - advice needed

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May 17, 2024 | 07:17 PM

Soundwave

Thread Starter

Instructor

Joined: Dec 2023

Posts: 113

Likes: 13

From: West Hollywood

Intermittent start and stall - advice needed

1994 LT1 6spd

Issue

Intermittent crank no start, but usually starts cold
Consistent stall appx 5 mins after starting. Car can be restarted after rest/cool down.

Symptoms/Observations

Stall seems to occur at idle/decel (coming to stop light or sign) @ temp = 180-190
Feathering accel prevents stall
Car will not restart for 5-10 mins, presumably after the engine cools
High and sticking idle, intermittent but particularly if I am at around 2500 RPM, it wants to stick around 1300 as I let my foot off. If I tap the accel it will drop to around 800 per my dash tach.
Voltage @ 15-15.2 on display when car is running (seems a bit high). Current cold voltage is 12.7. (@ batt on multimeter)
Instrument cluster dims/flickers as car comes to idle/decreases RPM when I am not on accel. Map lights flicker on idle
During crank/no start ABS and ASR on DIC flicker wildly, otherwise DIC is normal
No DTC's - C12 in mode 1 and 3xdash in 4 and 9. No H codes

Battery tested well and was fully recharged. When the car starts it is an easy start and it runs perfectly until the stall. I wonder if it is related to the open/closed loop changeover given it seems to consistently happen @ around 180. It could be possible I have more than one issue and timing is coincidental. Alternator, ECM, IAC are coming to mind as possibilities. Maybe ICM.

I'm spinning my wheels on diagnostics even with an FSM since these are intermittent and I don't have any codes. If anyone can offer advice or point me toward FSM procedures to follow I would greatly appreciate it.

Last edited by Soundwave; May 17, 2024 at 07:44 PM. Reason: added a symptom

May 24, 2024 | 11:42 AM

Brandon Koller

Intermediate

Joined: Oct 2023

Posts: 48

Likes: 0

I have a 91 l98 so not the lt1 but I had similar stalling issues with my car and what solved mine was cleaning the iac sensor. For the won’t start up until it cools down I’ve heard that the icm (ignition control module) has an issue were if the icm is bad when the car heats up it stalls and won’t start up until it cools down. Again I have an l98 so I’m not 100% sure about the lt1 but I’m trying to throw out some ideas.

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