Help! Stumped in Indiana.....

[roger_dale38]

92 LT1
Intermittent no start. Random stopping while driving. Not throwing any codes. Fuel pressure is good. When it does decide not to start, wait anywhere from a few minutes to 1/2 hour, starts right up. When decides to shut down while driving (just like you turned the key off) I get a service ASR light,climate control is flashing it's "off" light and blower motor may be running. I carry my Snap-on OBD-1 diagnostic scanner with to take readings when it happens. No codes. I replaced Opti-Spark less than two years back. I have 78,000 miles on it. I've been reading up on this issue and hear that it could be ECM, CCM or a communication issue between the two. Any ideas or suggestions would be greatly appreciated.

Thanks in advance,
Dale

 

[John Robinson]

The list of possibility's is a long one. First is the grounds (It doesn't cost anything to clean them all ) Bad Grounds mean no communication with the ECM. Vats going bad. Corroded wire connectors. Heat sink grease between the coil and engine block needs replacement. Check the FSM section on no start conditions. If you have an OBD I scanner then you need the FSM if you don't have it. The diagnostic charts will take you through all the possibility's by first checking all the circuits before it even suggests replacing any parts. Good luck and keep us informed on how it goes. There will probably be several very knowledgeable people that will chime in with more specific things you can do.

 

[i10fwy]

I had a similar problem, it was as simple as the key! Apparently the chip had worn. I used a new key and the problem stopped.

Hope this helps

i10fwy

 

[John Robinson]

On top of the opti is an electrical connector. If the water pump or a hose is spraying a fine mist of water on it the engine will shut down until it drys out. The dry out takes about 30 min on a fully hot engine then it will restart. Look for a leak in the water pump.

 

[roger_dale38]

On top of the opti is an electrical connector. If the water pump or a hose is spraying a fine mist of water on it the engine will shut down until it drys out. The dry out takes about 30 min on a fully hot engine then it will restart. Look for a leak in the water pump.

Thanks for the feedback John.
As of today, this is where it stands.
I replaced the optispark and a new water pump 2 years ago. No evidence of any leakage.
I just replaced the coil,the ICM,plug wires,TPS and an O2 sensor. Checked as many body and frame grounds as I could find. I did find a little corrosion on the 4 pin connector to the optispark. Cleaned that and have checked continuity all the way back to the ECM. With the key on I am getting 12 + volts to the optispark. I have 42 lbs of fuel pressure. I do not have any codes. It will start and I can drive it about 1-2 miles and it's like someone turned the key off. Wait about 5-10 minutes and it starts right back up. As I said though,it's not throwing any codes. Truely has me buffaloed. Not sure where to go next. Do you think ther might be an issue with the CCM?

 

[93Rubie]

Can you let it sit in the garage and idle? Does it die in there?

If it does, I would let it die and immediately try to restart, if it does not, immediately try to treat it as a no start diagnosis.
Picking up a inline spark checker might be a good idea. Put it inline with the main coil wire going to the Cap on the Opti-Spark. When the car dies, have someone crank it and see if it flashes. If that is ok, get a test light or a noid light and see if the injectors are pulsing when you crank. You might have to do this a few times to get it narrowed down if it restarts after 10 minutes or so. Work quick.

 

[John Robinson]

From what you describe it sounds like the car runs tell it gets up to a certain temperature and then shuts down. After it cools off a bit it will restart. That is what I think you are saying. If so I would start to look at the sensors involved in when it is in closed loop and then when in open loop. According to my FSm in closed loop the ecm is controlling fuel delivery according to the oxygen sensor voltage. In open loop the ecm ignores the oxygen sensor voltage and bases the amount of fuel to be delivered on the TP sensor, engine coolant, and Map sensor inputs only.

All the sensors mentioned in the open loop are grounded together in a bundle in the wiring harness. You will have to follow the wires back along the harness until you find a group of wires all together in a Black electrical tape wad. I f yours is like mine was it is all corroded and the ecm is not getting good signals from those sensors. When you take the ground bundle apart use a continuity tester to check for broken wires back to the electrical connectors.