Crazy car driving me crazy!!!
Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
Anyone else ever had this happen? Ill tell you, it's a HUGE PITA when your traveling! I have to get up at 2:00 in the morning and go outside to start the car to warm it up for the next morning's drive....
Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
I have tried everything I can think of to deal with it. I'm not a tuner, and have no skills in that area. Obviously, this is a very unusual problem. I'm hoping for a knowledgeable tuner to chime in that has had this same problem. I believe it is a problem somewhere in the TB, MAF, or maybe the TAC. It SUCKS!! I'm almost 72 years old, and starting to look ahead to the point of someday selling it. I'd hate to see someone else struggle with it. If I sell it in the summer, buyer will be good until temps drop to under 67°. On the other hand, I have to do what I have to do. This is a Helluva corner I'm finding myself in, I'll tell you.....
TECH Senior Member
Joined: Jun 2016
Posts: 22,293
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From: Central Cal.
I have tried everything I can think of to deal with it. I'm not a tuner, and have no skills in that area. Obviously, this is a very unusual problem. I'm hoping for a knowledgeable tuner to chime in that has had this same problem. I believe it is a problem somewhere in the TB, MAF, or maybe the TAC. It SUCKS!! I'm almost 72 years old, and starting to look ahead to the point of someday selling it. I'd hate to see someone else struggle with it. If I sell it in the summer, buyer will be good until temps drop to under 67°. On the other hand, I have to do what I have to do. This is a Helluva corner I'm finding myself in, I'll tell you.....
I'm 73 and also would not need this sort of complication in my life! LOL!
Having said that, what all has been replaced so far? Just a quick list...
TECH Fanatic
Joined: Oct 2022
Posts: 1,778
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From: Louisiana
I have tried everything I can think of to deal with it. I'm not a tuner, and have no skills in that area. Obviously, this is a very unusual problem. I'm hoping for a knowledgeable tuner to chime in that has had this same problem. I believe it is a problem somewhere in the TB, MAF, or maybe the TAC. It SUCKS!! I'm almost 72 years old, and starting to look ahead to the point of someday selling it. I'd hate to see someone else struggle with it. If I sell it in the summer, buyer will be good until temps drop to under 67°. On the other hand, I have to do what I have to do. This is a Helluva corner I'm finding myself in, I'll tell you.....
Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
If only I knew wtf I was doing with tuning an EFI, I'd buy HPTuners, and with some help from some of you guys, I'd give a few things a try. I am real good with jetting carbs. Which is useless in this context. God knows it's cold enough right now in Florida. I'd have plenty of opportunities for <67° starts!!!!
TECH Fanatic
Joined: Oct 2022
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From: Louisiana
If only I knew wtf I was doing with tuning an EFI, I'd buy HPTuners, and with some help from some of you guys, I'd give a few things a try. I am real good with jetting carbs. Which is useless in this context. God knows it's cold enough right now in Florida. I'd have plenty of opportunities for <67° starts!!!!
Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
Since it was brought up that my tune seems to have been based on this, can any of you explain why I would need a vacuum referenced fuel pressure regulator? Is this something a FI engine would need moreso than a NA engine would? I plan on calling my tuner on Thursday, and will report back what his response is.....
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Verdad Gallardo Thread Starter
Joined: Sep 2004
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From: Michigan & Florida
OK, a couple of updates. Called Tuner. He was floored when I told him the injector data was incorrect. He says he remembers me telling him that I have 42lb OEM LS7 injectors. Why the file is referencing 36lb injectors, he doesn't know. Our best guess is the first 427 I had did use 36lb injectors, and it somehow carried over to the new tune. He is pretty sure he entered the 42lb spec. He says it's possible it didn't populate, or he remembered me giving him the 42lb data, but he could've been sidetracked somehow, and it never got entered. At any rate, the tune is based on 36lb, instead of the correct 42lb injectors. He agrees that everything in the tune would have had to be altered to compensate for the wrong injector size. I ran a couple of other things guys saw by him, and he agreed that some of the data was probably not able to be transferred/altered enough to compensate for the wrong size. He said he'll send me the cold start files, both over 67°, and under, when he can. He's taking a couple-three weeks off for a vacation and to work on his own stuff. So it may be awhile, maybe mid December, before I get any new info. I'll post it when I get it. A big THANK YOU VERY MUCH to everyone who has tried to help me out here. If it weren't for forum members, the incorrect data may have never been exposed. THANKS AGAIN, GUYS!!!
Last edited by grinder11; Nov 24, 2025 at 09:23 AM.
Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
Since it was brought up that my tune seems to have been based on this, can any of you explain why I would need a vacuum referenced fuel pressure regulator? Is this something a FI engine would need moreso than a NA engine would? I plan on calling my tuner on Thursday, and will report back what his response is.....
So you can make either style work, but if you have a vacuum/boost referenced regulator, it makes the effective pressure drop across the injector always the same. This is more important with FI, because if you were to be running 30lbs of boost on a base fuel pressure of 45psi, then without a referenced regulator your effective fuel pressure across the injector would only be 15psi. Without FI the difference can only be a few psi anyway, so it is not as important. However, whichever style you have MUST be reflected in the injector data in the tune in order for things to work properly.
I'm not saying that has anything at all to do with his current issue. I was just answering a question he seemed to be interested in.
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Joined: Oct 2022
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From: Louisiana
I would climb under it with a heat gun and put some heat on the crank position sensor and see what happens, next id get under the dash with a voltage meter and check the tdr. Id also check the ignition switch. Id say check the temperature sensor but id think it would still turn over if that causing a false cold to ecu. Long story short, heat and voltage meter would be my best friends on this.
Last edited by Tommy42088; Nov 25, 2025 at 06:53 AM.
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From: Louisiana
This is chat gpt answer
**A 2000 C5 Corvette that will not start below about 67°F and starts only when heat is applied to the front bumper is almost always caused by a failing Engine Coolant Temperature (ECT) sensor or damaged ECT wiring. On cold mornings the ECT sensor or its connector contracts and creates an open-circuit, making the PCM think the coolant temperature is –40°F. This triggers extreme cold-start enrichment, flooding the engine and causing the idle air control valve and throttle plate to slam shut as the PCM tries to stabilize the impossible mixture. Because the 2000 model uses a cable-driven throttle, the throttle closing is a mechanical reaction to over-fueling, not an electronic throttle fault. When you warm the front bumper, you are heating the ECT sensor area and wiring harness enough for the resistance to return to normal, the PCM gets a realistic temperature reading, and the car starts immediately. The fix is to replace the ECT sensor (located on the driver-side cylinder head under the throttle body) and inspect the connector and wiring for corrosion, cracked insulation, or broken conductors. The repair is quick and inexpensive and is the classic solution for C5 Corvettes that will not start in cold weather and only start when heat is applied to the front end.**
**A 2000 C5 Corvette that will not start below about 67°F and starts only when heat is applied to the front bumper is almost always caused by a failing Engine Coolant Temperature (ECT) sensor or damaged ECT wiring. On cold mornings the ECT sensor or its connector contracts and creates an open-circuit, making the PCM think the coolant temperature is –40°F. This triggers extreme cold-start enrichment, flooding the engine and causing the idle air control valve and throttle plate to slam shut as the PCM tries to stabilize the impossible mixture. Because the 2000 model uses a cable-driven throttle, the throttle closing is a mechanical reaction to over-fueling, not an electronic throttle fault. When you warm the front bumper, you are heating the ECT sensor area and wiring harness enough for the resistance to return to normal, the PCM gets a realistic temperature reading, and the car starts immediately. The fix is to replace the ECT sensor (located on the driver-side cylinder head under the throttle body) and inspect the connector and wiring for corrosion, cracked insulation, or broken conductors. The repair is quick and inexpensive and is the classic solution for C5 Corvettes that will not start in cold weather and only start when heat is applied to the front end.**
Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
I was responding to him because he seemed excited to find out the injector data was incorrect. A good find but im not fully convinced that wrong injector data could cause i can to not start under 67 degrees. Run bad? Yes , struggle to start? Yes, but only crank above 67 degrees? Hmm doesnt add up to me. I wish he was closer to me because id honestly like to see this is person, something has got to be shorting out, imo. Losing crank, rpm, something along that nature.
I would climb under it with a heat gun and put some heat on the crank position sensor and see what happens, next id get under the dash with a voltage meter and check the tdr. Id also check the ignition switch. Id say check the temperature sensor but id think it would still turn over if that causing a false cold to ecu. Long story short, heat and voltage meter would be my best friends on this.
I would climb under it with a heat gun and put some heat on the crank position sensor and see what happens, next id get under the dash with a voltage meter and check the tdr. Id also check the ignition switch. Id say check the temperature sensor but id think it would still turn over if that causing a false cold to ecu. Long story short, heat and voltage meter would be my best friends on this.
Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
This is chat gpt answer
**A 2000 C5 Corvette that will not start below about 67°F and starts only when heat is applied to the front bumper is almost always caused by a failing Engine Coolant Temperature (ECT) sensor or damaged ECT wiring. On cold mornings the ECT sensor or its connector contracts and creates an open-circuit, making the PCM think the coolant temperature is –40°F. This triggers extreme cold-start enrichment, flooding the engine and causing the idle air control valve and throttle plate to slam shut as the PCM tries to stabilize the impossible mixture. Because the 2000 model uses a cable-driven throttle, the throttle closing is a mechanical reaction to over-fueling, not an electronic throttle fault. When you warm the front bumper, you are heating the ECT sensor area and wiring harness enough for the resistance to return to normal, the PCM gets a realistic temperature reading, and the car starts immediately. The fix is to replace the ECT sensor (located on the driver-side cylinder head under the throttle body) and inspect the connector and wiring for corrosion, cracked insulation, or broken conductors. The repair is quick and inexpensive and is the classic solution for C5 Corvettes that will not start in cold weather and only start when heat is applied to the front end.**
**A 2000 C5 Corvette that will not start below about 67°F and starts only when heat is applied to the front bumper is almost always caused by a failing Engine Coolant Temperature (ECT) sensor or damaged ECT wiring. On cold mornings the ECT sensor or its connector contracts and creates an open-circuit, making the PCM think the coolant temperature is –40°F. This triggers extreme cold-start enrichment, flooding the engine and causing the idle air control valve and throttle plate to slam shut as the PCM tries to stabilize the impossible mixture. Because the 2000 model uses a cable-driven throttle, the throttle closing is a mechanical reaction to over-fueling, not an electronic throttle fault. When you warm the front bumper, you are heating the ECT sensor area and wiring harness enough for the resistance to return to normal, the PCM gets a realistic temperature reading, and the car starts immediately. The fix is to replace the ECT sensor (located on the driver-side cylinder head under the throttle body) and inspect the connector and wiring for corrosion, cracked insulation, or broken conductors. The repair is quick and inexpensive and is the classic solution for C5 Corvettes that will not start in cold weather and only start when heat is applied to the front end.**
Last edited by grinder11; Nov 25, 2025 at 11:30 AM.
Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
I'll also add that earlier this last summer, I had removed the alternator, and when I put it back on, it pivoted before I could get another bolt in it, and slammed against the bracket and valve cover. When this happened, I had the ECT sensor pigtail in the wrong place at the wrong time. The alternator nearly cut the pigtail thru. I had to pull the alternator again, and I stripped each end of the severely damaged wire, soldered them together, and used shrink tubing to protect the wiring. I know its fixed correctly, but when I tried to start the car before I knew the wiring was damaged, it was really rich, and one of, or both, the cooling fans came on.