96 Lt4 Mystery
Thread Starter
Instructor
Joined: Aug 2017
Posts: 246
Likes: 6
96 Lt4 Mystery
The car just died. Has started once cool only to warm up and die after a few minutes.
I had some MAF sensor related codes, so i replaced it. The battery was a bit weak so i replaced it.
So in the spirit of heat related problems, i inspected the coil and ICM. They looked like originol equipment and looked really bad. You guessed it. I replaced them.
STILL NO JOY!!!
I am looking for suggestions, tests and proceedures etc. I do have the factory service manual. What section would you think i should be looking in.
I am supposed to be taking this car to the C4 Gathering in a couple weeks. Really bad timing for sure!
Thank you for your input.
MikieG
I had some MAF sensor related codes, so i replaced it. The battery was a bit weak so i replaced it.
So in the spirit of heat related problems, i inspected the coil and ICM. They looked like originol equipment and looked really bad. You guessed it. I replaced them.
STILL NO JOY!!!
I am looking for suggestions, tests and proceedures etc. I do have the factory service manual. What section would you think i should be looking in.
I am supposed to be taking this car to the C4 Gathering in a couple weeks. Really bad timing for sure!
Thank you for your input.
MikieG
Racer
Joined: Sep 2017
Posts: 452
Likes: 55
From: Marianna Fl
Check fuel pressure. Had an LT1 that would run like a beast cold, get about 20-30 minutes int the drive and it bogged and cut out. Turned out to be a bad fuel pump and clogged filter ( tank rust was the cause). Although you shouldn't have tank rust you may still have a fueling issue.
Thread Starter
Instructor
Joined: Aug 2017
Posts: 246
Likes: 6
I am aware of the opti spark issues. I amnot ruling it out. But you have to admit, the second an LT engine stutters, the oti is always blaimed immediately.
The items i replaced were already in need of replacing.
Really pises me off if it turns out to be so. I just flushed the coolant system.
The items i replaced were already in need of replacing.
Really pises me off if it turns out to be so. I just flushed the coolant system.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
Check fuel pressure. Had an LT1 that would run like a beast cold, get about 20-30 minutes int the drive and it bogged and cut out. Turned out to be a bad fuel pump and clogged filter ( tank rust was the cause). Although you shouldn't have tank rust you may still have a fueling issue.
Would be good to check for spark also.
Racer
Joined: Mar 2018
Posts: 411
Likes: 97
From: Las Vegas
See if this helps:
https://www.youtube.com/watch?v=famCZkXppYM
Please don't throw any more parts at the problem till you have explored the Opti problem. Your symptoms sound like this is something you shoudl consider.
https://www.youtube.com/watch?v=famCZkXppYM
Please don't throw any more parts at the problem till you have explored the Opti problem. Your symptoms sound like this is something you shoudl consider.
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Brett Foote
Race Director
Joined: Oct 2012
Posts: 17,338
Likes: 6,510
From: Melbourne, FL
Doesn't sound like an opti to me at all.
I agree, check fuel pressure. The start when cold but then dying when warm normally sounds like icm or coil, but with those ruled put I'd check fuel. Could by a leaky regulator, or a blockage in the delivery system (filter perhaps)?
I agree, check fuel pressure. The start when cold but then dying when warm normally sounds like icm or coil, but with those ruled put I'd check fuel. Could by a leaky regulator, or a blockage in the delivery system (filter perhaps)?
Race Director
Joined: Sep 2001
Posts: 14,674
Likes: 751
From: NEwhere Ohio
As electronics get hot, short circuits occur.
Outside of vapor-lock issues of old carb’d cars, ive never heard of a the fuel system shuts down when it gets hot.
You’ll get a mix of replies on here from early tpi c4 guys that had failure prone early injectors whereas the lt1 multec? style is pretty bulletproof.
this is why id look more at the ignition, with a big emphasis on the optispark.
Outside of vapor-lock issues of old carb’d cars, ive never heard of a the fuel system shuts down when it gets hot.
You’ll get a mix of replies on here from early tpi c4 guys that had failure prone early injectors whereas the lt1 multec? style is pretty bulletproof.
this is why id look more at the ignition, with a big emphasis on the optispark.
Last edited by dizwiz24; May 6, 2018 at 02:26 PM.
Drifting
Joined: Mar 2018
Posts: 1,361
Likes: 400
From: DFW TX
I own a fuel pressure gauge to identify this exact issue and have helped several friends, family members and coworkers over the years.
As previous members have stated, I concur... The first thing I would do is attach my fuel pressure gauge, if that isn't the issue I would look at the other items that succumb to heat soak, i.e. coil and relays.
Race Director
Joined: Sep 2001
Posts: 14,674
Likes: 751
From: NEwhere Ohio
Happens all the time and it is a very very typical symptom of a failing electric fuel pump. I have seen it multiple times over the years. It is probably a crap shoot as to whether it is the electronics within the pump failing or the pump physically seizing when the heat soak sets in. Sometimes the relays will act this way too, as in a heat soaked starter relay which is very typical as well. When the symptoms start, sometimes you can coax the pump along by keeping the tank full which keeps the fuel/tank temp down.
I own a fuel pressure gauge to identify this exact issue and have helped several friends, family members and coworkers over the years.
As previous members have stated, I concur... The first thing I would do is attach my fuel pressure gauge, if that isn't the issue I would look at the other items that succumb to heat soak, i.e. coil and relays.
I own a fuel pressure gauge to identify this exact issue and have helped several friends, family members and coworkers over the years.
As previous members have stated, I concur... The first thing I would do is attach my fuel pressure gauge, if that isn't the issue I would look at the other items that succumb to heat soak, i.e. coil and relays.
Im not saying your experience isnt true.
Have you seen fuel pump/when hot issues on a c4 Lt1? Or some Ford or Chrysler with EFI ?
Ive been on here awhile and havent seen it - yet have seen tons of optispark problems.
Race Director
Joined: Oct 2012
Posts: 17,338
Likes: 6,510
From: Melbourne, FL
I would counter that you've seen lots of issues that get blamed on Optis. A lot of them are something else that gets dome at the same time, like plugs, wires, coils, or ICMs.
Thread Starter
Instructor
Joined: Aug 2017
Posts: 246
Likes: 6
As i said earliwr. I had a list of defects i already knew needed repair. I handled them myself to keep repair labor costs down.
The heat issue immediately had me thinking of coil and ICM. Now with them changed, (could be bad outta the box ) with new ones, i feel like this could easily be fuel pump, filter or Opti related.
My mechanic goes on jury duty tomorrow. Hell be there all week. Looking like this LT4 wont be at the Gathering this year.
The heat issue immediately had me thinking of coil and ICM. Now with them changed, (could be bad outta the box ) with new ones, i feel like this could easily be fuel pump, filter or Opti related.
My mechanic goes on jury duty tomorrow. Hell be there all week. Looking like this LT4 wont be at the Gathering this year.
Drifting
Joined: Mar 2018
Posts: 1,361
Likes: 400
From: DFW TX
Nope, never. Probably has never happened in the history of the world of LT1 C4 Corvettes.
Thread Starter
Instructor
Joined: Aug 2017
Posts: 246
Likes: 6
Drum roll please.... But first. This thread had alot of great advice. Last year my other 96 died. Turned out to be ICM. This one.... wait for it...
Opti spark!!!
My son is just amazed by the smooth power of the LT4 now!
Opti spark!!!
My son is just amazed by the smooth power of the LT4 now!
