Please read! 93 5.7 TBI suburban stalling when hot!
March 23rd, 2019, 9:17 PM
#1
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Please read! 93 5.7 TBI suburban stalling when hot!
Hello to everyone reading this thread, I have been working though a large issue with my 5.7L TBI engine in my 93 suburban and have hit a wall.
The engine starts and runs normally when cold. However, once I've been driving for a while and it comes up to temp, it stalls when the rpms approach idle. Once stalled, it will crank but not start without the aid of starting fluid. Once restarted, it will run normally, as long as there is throttle input. Once my foot leaves the gas pedal however and the rpms drop, it dies.
The things I have tested are as follows:
TPS - no dead spots on multimeter.
Idle controller (on TB) - actuates freely.
EGR valve - holds vacuum.
Fuel pressure - 12 to 13PSI at all times (key on, cranking, cold idle, running in gear).
Timing - set to factory spec.
Obd - no codes.
Distributor - clean and all connectors secure.
Things replaced:
Fuel filter.
ocolant temp sensor (to computer).
Oil pressure sensor.
O2 sensor.
Ignition coil.
I've run out of things to test...I think that something must either be cutting fuel to the injector or cutting spark at idle speeds. If anyone has advice, please share it here! -S
The engine starts and runs normally when cold. However, once I've been driving for a while and it comes up to temp, it stalls when the rpms approach idle. Once stalled, it will crank but not start without the aid of starting fluid. Once restarted, it will run normally, as long as there is throttle input. Once my foot leaves the gas pedal however and the rpms drop, it dies.
The things I have tested are as follows:
TPS - no dead spots on multimeter.
Idle controller (on TB) - actuates freely.
EGR valve - holds vacuum.
Fuel pressure - 12 to 13PSI at all times (key on, cranking, cold idle, running in gear).
Timing - set to factory spec.
Obd - no codes.
Distributor - clean and all connectors secure.
Things replaced:
Fuel filter.
ocolant temp sensor (to computer).
Oil pressure sensor.
O2 sensor.
Ignition coil.
I've run out of things to test...I think that something must either be cutting fuel to the injector or cutting spark at idle speeds. If anyone has advice, please share it here! -S
March 24th, 2019, 1:08 AM
#3
I'm here for the party
since it starts on starting fluid i would think its not spark related but an air/fuel issue. could be the IAC valve
Symptoms of a Defective I.A.C.
high or low idle
engine dies at idle
severe high idle
I.A.C.
(Idle Air Control)
Symptoms of a Defective I.A.C.
high or low idle
engine dies at idle
severe high idle
Testing
Terminals A to B should be 40 to 80 ohms
Terminals C to D should be 40 to 80 ohms
Terminals A to D should be infinite
Terminals B to C should be infinite
i had a similar issue with a truck that i was working on for a friend. but it seamed like the injectors were dumping fluid and was blowing black soot. i went through all the sensors and everything tested fine. the egr valve when depressed would make the engine almost stall. it was running low on fuel so i added a few gallons, in trying to start it the battery had died. so i swapped it with one from another truck and the truck starts running 100% better. i dont know what it was it was either a poor battery connection or bad gas.
also one more thing next time it stalls try starting it with the pedal floored. this tells the ecm to "clear flood" mode and will turn the injectors off or limit how much fuel they spray.
Symptoms of a Defective I.A.C.
high or low idle
engine dies at idle
severe high idle
I.A.C.
(Idle Air Control)
Symptoms of a Defective I.A.C.
high or low idle
engine dies at idle
severe high idle
Testing
Terminals A to B should be 40 to 80 ohms
Terminals C to D should be 40 to 80 ohms
Terminals A to D should be infinite
Terminals B to C should be infinite
i had a similar issue with a truck that i was working on for a friend. but it seamed like the injectors were dumping fluid and was blowing black soot. i went through all the sensors and everything tested fine. the egr valve when depressed would make the engine almost stall. it was running low on fuel so i added a few gallons, in trying to start it the battery had died. so i swapped it with one from another truck and the truck starts running 100% better. i dont know what it was it was either a poor battery connection or bad gas.
also one more thing next time it stalls try starting it with the pedal floored. this tells the ecm to "clear flood" mode and will turn the injectors off or limit how much fuel they spray.
Last edited by Irish_alley; March 24th, 2019 at 1:22 AM.
March 26th, 2019, 6:19 PM
#6
I'm here for the party
dont mean to jinks you or anything but in my experience if an icm goes up it the engine wont restart till the icm cools down. its odd how throttle response effects it but its an electronic so i guess anything is possible
