[warmachine]

Hi I'm stumped on this issue and felt it was time to ask the experts that could maybe help solve it.

Engine is a basically stock 1993 LT1 with VATS delete (removed in eeprom on ECM). It has been running driving great for 2 year plus. All of the sudden I have this issue where after driving for maybe 10-15mins it just dies. Hard dies. Will crank but not spit or putter or anything. If I wait about 30 minutes it will start right up like nothing ever happened.

Trouble light I know does work (had different issue before) but with this issue there is no blink code and no fans come on. To make matters more confusing, I have idled the car in the driveway for over 45 minutes and it will not have the issue. Fans even come on at right temp, then go off, temperature stays in check and just keeps running.

Only when driving for about 10-15minutes, then dies so i have to pull over the side of the road and wait the 30 minutes. Happened 3 times so far so I have no faith anymore to drive it any distance.

If you have any ideas for what this could be I'm all ears and willing to give it a shot at this point.

 

[shoebox]

First: scan for trouble codes. Some of the killer codes don't make the light come on.

Then, check for spark and fuel when it won't start. That should give a starting place.

 

[cocobolo95]

Do check for the silent ignition codes that don't turn on check engine light. Dtc 16 opti low res signal missing, and 41 & 42 both icm codes will leave you dead in the water when set. 93 aldl can have pins A & B shorted together to check codes. Pic of 93 aldl is at shbox.com
#17 in reference area.

But icm would be the prime suspect. The optical sensor is also subject to heat failure, as well as a tired fuel pump no longer pumping when hot. Fuel pressure tester put on fuel rail will quickly confirm condition of fp when car dies.

Quick check for low res sensor working is to crank engine. If low res working, tach needle will show some rpm when cranking. Definitive metod of low & high resolution sensors is with an oscilloscope.

 

[warmachine]

Hi shoebox thanks for the reply. I have used your site before and it's a great source of info.

By scan for codes do you mean short ALDL pins A-B when the problem arises then wait for blink codes?

 

[warmachine]

thank you cocobolo that answers the question I had. I will short the pins but now I'm looking for ways to get the problem to happen again without driving it (because it seems to stall in the most inconvenient location). Just idling it will never happen. Too bad this 1993 ecm doesnt log faults like OBDII does.

 

[cocobolo95]

If you want the icm to fail, try using a hair dryer to heat it up while car is idling. A heat gun might work also, but make sure you use only the low setting on it.

 

[shoebox]

The ECM should store faults.

 

[warmachine]

Oh I didn't realize. I tried the last 2 times after I got home and it was just 12, but I wasn't waiting long enough and now I see that 41 comes up. Was probably coming up all along.

Anyway so sounds like I need a new one of them (rolls eyes). I think this was an issue for the previous owner of the motor because there is a custom non-factory looking bracket that moves the ICM off the head. Is there any more permanent term fix for this issue? Can any year LT1 ICM can be used?

Thanks again guys.

 

[sweetbmxrider]

Just spacing it off of the head and using some thermal paste like the stuff used building computers are the best ways to prolong icm life. It is a common failure on many cars using a similar setup.

 

[warmachine]

So as a follow up...I still have this issue. I replaced the ICM, twice. Once in September and it didn't work, so I took a break and played with my other projects.

2nd time was today and had a good feeling so I took it out. Welp, this time I stalled on a busy road and needed to be towed (was covered by roadside assistance through insurance thankfully). I had a meter with me this time and measured 12v going to the ICM from the coil which is good.

I have the pcm out of it's case now looking for anything that looks bad traces or burnt out devices it all looks good. Does anybody know if these pcms (16159278) are prone to issues?

 

[cocobolo95]

The pcm's used in lt1 cars are tough & reliable.

 

[dondon69420]

You need to check the optispark, that's what mine did when it went out in my 93.

 

[lf93formula]

I had this issue and after checking the ICM and Opti, it was a bad fuel pump. I would get about 7 miles from home and it would sputter briefly and then die. After some time it would restart and I could get it home. Check the fuel pressure. If it primes and the the pressure drops (not running) you have a fuel pump issue.

 

[dondon69420]

Yeah I didn't see everything that was posted until after I replied. Idk why my phone goes straight to the bottom of the page on this site, it's weird. Mine set a code 16 in my 93 when the opti died, I just didn't see that you scanned and had nothing. Glad it's fixed though.

 

[spfmarco]

Hi I'm stumped on this issue and felt it was time to ask the experts that could maybe help solve it.

Engine is a basically stock 1993 LT1 with VATS delete (removed in eeprom on ECM). It has been running driving great for 2 year plus. All of the sudden I have this issue where after driving for maybe 10-15mins it just dies. Hard dies. Will crank but not spit or putter or anything. If I wait about 30 minutes it will start right up like nothing ever happened.

Trouble light I know does work (had different issue before) but with this issue there is no blink code and no fans come on. To make matters more confusing, I have idled the car in the driveway for over 45 minutes and it will not have the issue. Fans even come on at right temp, then go off, temperature stays in check and just keeps running.

Only when driving for about 10-15minutes, then dies so i have to pull over the side of the road and wait the 30 minutes. Happened 3 times so far so I have no faith anymore to drive it any distance.

If you have any ideas for what this could be I'm all ears and willing to give it a shot at this point.

Sounds like it might be the PCM, when they get old the pc boards get brittle and crack when they vibrate or heat up they can break the circut. After cooling down it reconnects. Some times banging on the PCM with a plastic hammer while the care is warm and running and if it shuts down you know its the PCM.