I have an intermittent problem with my ignition. It randomly cuts out after warming up and sometimes stalls. Restarts easily most of the time.
These episodes do not throw any codes, the only codes I have is a 28 code because the last owner wired the fans to be on all the time which I'll fix after this problem is solved.

93 Base Lt1 with no mods that I am aware of, 141000 miles/ Just traded a perfectly good Yukon XL for it in, told the wife that it gets much better mileage than the truck did but her patience is wearing thin and I am seeing an air mattress in my future if I don't get to the bottom of this problem.

I've replaced the following items
opti spark
Plug wires
water pump
fuel pump and strainer
Fuel filter
Air filter
both cats and 02 sensors - high flow direct fit
replaced intake manifold gasket for minor oil leak
EGR valve
IAT sensor
TPS sensor
MAP sensor

Ohm tested the injectors, cold they are all between 12.3 and 12.5, hot between 12.8 and 13.0

I removed the ICM and took it to Autozone and they tested it on their Wells machine, supposedly heats it up and places it under a load. It checked out OK

Checked the fuel regulator, appears to be working OK, no fuel smell from vacuum side of regulator

When the car is cold it runs great and runs great when warm outside of this ignition cut out that I am experiencing. Shifts are snappy and engine accelerates smoothly while driving through the rpm range, at least to 5000rpms without a problem which is about as high as I've gotten her.

I'm thinking that if the coil were bad when it warmed up and started to exhibit these symptoms they wouldn't just go away. My voltage is always between 14.3 and 14.7 volts, although a couple of times when I activated the turn signal or lights the voltage breifly dropped to 13.8.

I am out of ideas, almost out of money, and would really appreciate any advice you folks would be willing to share. So far I don't feel bad about replacing any of the parts above, the opti and water pump were clearly bad (threw codes 28 and 64) water pump was leaking. One of the cats was rattling pretty bad when it warmed up and the other was a white box POS that was welded in.

 

I believe those injectors seem on the low side call Jon @ FCI. I also have to say the LT motors could be different then my L98 as far as ohms go. i would also get the correct fuel pressure reading using a gague

 

Floridamale - thanks for the quick reply. I'll give Jon a call and see what he thinks. I didn't look closer at the injectors before now because of how easy the car starts cold, never more than 2 turns and typically catches on the first, the ohm readings that I got seemed consistent and the car ran so great outside of this problem.

 

Definately sounds like something electrical is heating up and failing. It could be the coil or a fuel pump relay. Since it restarts so easily, it might be hard to find.

 

Yep....that would be my luck. Had a 68 GTO where the distributor lead wire broke inside the insulation. Would warm up, insulation would expand, car would die, by the time it was towed back to base it would restart. Went through a few cycles before this mechanic on base figured it out.

What about the ECM?

 

ECM are generally reliable.

 

Paul, thanks for the heads up, I will replace the coil and fuel relay tomorrow and see what happens. I left a message for Jon at FIC as well to talk about the injectors.

 

This is soooo much different than my 75 vette was :-) Then again, it outruns and outrides that 75 by a wide margin as well!