I won't bore you with what I've been going through. I have a 1986 C4 Corvette. What I have dumbed it down to now is my car runs until it gets to around 193 / 194 / 196 coolant temp and then it dies. I believe it has a stock 195 thermostat. I had the water pump replaced a few months back and apparently the mechanic did not replace the thermostat. Should I replace the thermostat? How does the thermostat work? I think the car runs hot and it should come open and be fine til about 228. I'm not a mechanic, but somebody screwed me over for $800 and sent me the car back two different times with it still stalling. Frustrated and tired.

 

It's not a thermostat issue, you have something else going on. Just a FYI changing the water pump doesn't have to include the thermostat.

 

And, for reference sake, HEAT (i.e., "thermal failure") is generally a symptom of electrical failures. FUEL-AIR-SPARK: Which is changing as it reaches the 195º+ region? I'd want to see what an OBD-1 scanner or Tech-1 showed what was happening at "cutoff" temperature. For example, injectors susceptible to ethanol mixed fuels typically do not show their colors until AFTER reaching operating temperature. The resistance values (again AFTER warmed up) should all be within ± 1Ω (12ish or 14ish, depending on the injectors installed). Injectors from 93 on were alcohol tolerant, but if yours are pre-93s and you run or ever ran ethanol blended fuel, chances are they need to be swapped out for new (NEW - not [so called] "rebuilt") injectors.

 

where r u located? maybe someone close with a scanner could help. sounds like icm.

 

Wonder if your coolant temp sensor is wacked out? Anyone know when it goes into closed loop?
You need a diagnosis or youll throw parts at it all day long.

 

too. When the symptom occurs, does the car have spark, still?


Unfortunately, and OBD I scanner isn't going to show us much for a no-run condition....especially on the ignition side. You'll see the pick up coil (RPM reading), but that's about it. I'd simply start by checking for spark when it won't run.

 

Checking the spark condition is a good idea. Could also be fuel delivery as well through injectors that are going south. They can run fine until fully heat soaked, then they operate intermittently or stop completely. Checking the resistance of the injectors on a TPI car may be difficult during the moment it actually dies, unless there’s a back probe method through the ECU plug.

You mentioned not being a mechanic, so I won’t tell you now is the time to start learning but compile the information provided here by other posters to your topic and create a list from that to provide to a qualified mechanic to review the troubleshooting.

 

Also check ECM and connections for any corrosion. Does it only happen at those temps specified, or is consistent of when it is warming up? Like stated before it could be an issue when it goes into closed loop operation. If the ECM is starting to fail and it is affected by heat, or any connections that may expand as it gets warm.

Good luck.

 

Thank you all for your input, I truly appreciate it! I bought the car 3 years ago and it's always had a stalling issue (usually no codes are thrown) Here's what I've done so far with the car. New water pump last January in Iowa. Moved to Middle Tennessee in February, took it to the mechanic because the car was stalling when I would slow down to a red light. I would put it in neutral and she would fire up right away. Mechanic put on a new coolant temp sensor, said the stalling issue was gone, and 20 minutes of driving, it stalled again! Took it to same mechanic and he put on new catalytic converters. Mechanic said again the car didn't stall, 20 minutes later I'm driving, it stalled again! $800 down the drain ( plus parts $). After researching this forum, I put on a new O2 sensor and she fired up right away. Next day, stalling is back. Alternator was bad so I replaced it, she fired up perfectly, but crapped out the next day. I put on a new battery, fired it up, sounded great, she idled perfectly for 15 minutes last night so I drove it around my complex twice and that's when she heated up to around 195 and she stalled. She cooled down in less than 10 minutes, and I was able to get her back to my parking spot. To answer someone's question, this is the second time she has stalled at the 195 temp. She used to stall not until it got to around the 200 - 210 range. I understand how the fuel pump relay and the oil pressure switch work together, wondering if I should change the switch since my FPR was off the car for about a year before I realized it. Also, I do not hear my fuel pump whirring to turn on, but the car is running, so doesn't that that mean the fuel pump is okay and running? Sorry so long, but like I said, I am so tired and frustrated and I have searched and searched and searched this forum so much, I just need help with my very specific issue. Thanks so much! Oh, BTW, my connector for the OBD1 scanner is not working. 😢 The SES light does not come on until right when she dies.

 

P.S. I did put on a new idle air control valve, and a new ignition control module, and put electrical tape on the three of the five fuel pump relay wires that were stripped. Fuel pump relay is new. The mechanic did tell my son he thinks it's the wiring harness. A couple days ago when the car stalled, a guy from Firestone came over to jumpstart me and he noticed the wires between the battery and the firewall were smoking. Not the MAF relays, but the alternator wire and two other red, I think, wires. I put electrical tape on them, and now they don't smoke.

 

Was the insulation chewed off that they were making a short where they were smoking? Could you have a rodent problem? Does the car crank over when it dies? 3 things to make an engine run... spark, fuel, and compression... you have compression because it runs up to that point... 2 items left fuel or spark...so that being said the first thing I would do per your description is hook a fuel pressure gauge up to the fuel rail and bring the car to temp, watch the gauge to see if fuel pressure drops away right before it would die. That would indicate the fuel pump being shut down for some reason... maybe it heats up and stops, or maybe the computer is telling it to shut off. With that gauge attached, crank over the engine and see if the fuel pressure spikes to normal operating pressure while cranking. if it does you know the fuel pump is operating. That being said i would start looking towards ignition.

 

Wires didn't look that bad, not chewed, they were worn in maybe four or five spots, and only one wire was exposed, but it was only the size of half of a pencil eraser. The Firestone guy said the red wire was hot to the touch, and he burned his finger on that one exposed wire. I've never seen smoke behind there, and the wires did not feel hot last night after letting the car idle.

 

So that should have fixed your short on that wire. " I've never seen smoke behind there, and the wires did not feel hot last night after letting the car idle."

 

I've suspected my fuel pump for some time now, especially since I can't hear the whirring sound anymore. I did have a neighbor help me once with the fuel rail. There was pressure at the rail, we were anticipating a stall, so when it did stall he checked it right again and there was no fuel on the rail. Oh, and the car will restart after cooling down for about 10 minutes.

 

sounds like fuel pump to me, or possible fuel pressure regulator

 

Fuel pump replacement is pretty simple on those. Right under fuel fill door.

 

link to fuel pump replacement

 

Thanks for your input, and thanks for the link to the fuel pump replacement video! Where is the fuel regulator located? Should I check that first if it's not in the tank? Oreillys has a Precision brand fuel pump for $67 Lifetime warranty, and also a Master Pro brand for $47 one year warranty. I'm wondering which one I should buy cuz I'd love to save money, but I don't know the difference in quality between the two brands.

 

Closed loop transition should be about 160F. However, even if that sensor were completely and utterly out of whack, the car would still run (albeit not optimally). This actually happened to another member with a '95 recently where his sensor was sending a wildly fluctuating signal constantly. So the coolant temp is a red herring here; the actual answer, as others in the thread have pointed out, is either heat soak itself affecting another component (such as the coil), or time itself.

As for OP's comment about the oil pressure switch, just to be crystal clear, this switch does not and cannot cut off your engine unless you have completely bypassed the CCM, or the CCM has failed. The CCM is what controls your fuel pump relay. If the CCM fails, has been bypassed, or has been commanded not to run the fuel pump relay, it can be overridden by the oil pressure switch signal. However, if the CCM is operating normally, then the oil pressure switch has zero authority over the fuel pump relay.

 

When I replaced the ignition control module, I did not replace the ignition coil. Should I have? Also, a neighbor who works on large FedEx trucks thinks it's a timing issue. What does that mean? I appreciate everyone's help! For the $800 I paid the mechanic, I could have thrown parts at it all day long for that amount of money!