I am often having a problem starting my C5 after I've driven it enough to get it completely warmed up. Now it's at a dealership and they are working with GM to try to figure out the problem. They've had it for a week.Please help, I need my baby back. Additional info: 56k, ECM replaced due to the battery corrosion issue, died once out of the blue at a traffic light and one time that it didn't start right away things got weird, I didn't run ther battery down but it sota seemed like it. after trying to start it a few times it acted very weird, as if it was trying to start with only one cylinder firing or something. I called for a tow, but befor they could get there I got it to start.

Update! Update!
The jury is in!
Drum roll please.....
Aftermarket key ( from a reputable locksmith ) was the problem. The dealership ( Titus Will in Parkland Wa ) could not figure out what was wrong, ( and did not charge me a penny ) but referred me to a Corvette only shop ( Corvettes of Auburn ( Wa ) ). I did not ask why but they said the aftermarket key and the ignition switch were bad. Both replaced and so far no problem.

 

Problem-starting-when-warm is often a really not fun one to diagnose. Could be a bunch of stuff. In an older car, you might say it's vapor lock!

Weird stuff I've heard of:

- Bad starter, or weird starter, that gets heat-soaked and can't crank properly. Or a bad solenoid.
- Bad grounds, bad power supply (poor battery or poor alternator), and bad connections in the power supply path, are always a suspect for me for weird and hard to explain behavior.
- Is there any aftermarket or modified wiring in the car? Always a good thing to check.

Remember, for an engine not starting or starting funny or running funny, there are three basic things to check: the air, the fuel, and the spark.

Spark comes from a myriad sensors and through eight coils and eight wires and eight plugs; so anything in the sensor -> ECU -> plug path can be at issue, including the power supply for the sensors. Additionally, in this case, the cranking itself comes from the starter and that path may have issues.

Air comes from the intake, where you should at minimum check it has a clean and unobstructed path to flow, and that it is metered properly by the MAF and that the MAP shows good data. It goes out the exhaust headers, through the cats, through the cross-over, out the mufflers. You have to make sure that the output path is unobstructed (your cats aren't clogged or overheating, which could be hot-related issues), and that your O2 sensors read properly.

Fuel comes from the fuel tank, through the pump, through the filter, through the injectors. You have to make sure your injectors are firing properly when hot, that your fuel pump isn't overheating (again, a hot-issue, where some component may be cooled just enough with flow but not when it's hot and not pumping), that your fuel filter isn't clogged.

And I'm sorry to say, but that's often hard to diagnose in a hot condition.

You can start with by replacing all the consumables - plugs, wires, air filter, fuel filter - and cleaning stuff - the MAF, the throttle body. It may well not help, but then again, it won't cost much and it's good to refresh that stuff anyways.

 

Moved to C5 Tech.

 

It's been at a stealership AND they're working with GM trying to diagnose it ??...WHOA !!!!...if it's at a stealership what can we do from this end ??...what are the exact symptoms ??...crank no start, no crank no start, start and stall ??.

 

In addition to what has been posted you entioned the battery corrosion issue and depending on how bad that was , it could relate to a starting problem. also on the old chev engines when they got hot the starter motor would drag. not sure if the ls 1 does that but others can chime in on that

 

A symptom of the ignition switch going bad can be dying at a stop, also starting but reduced power warning, running very badly, low voltage warning and a host of other warnings on the DIC. Turning of the ignition and attempting a restart sometimes results in a normal start but leaves a check engine light. No codes or a host of codes.

Difficult to diagnose.

 

This is driving me crazy. I have a C5 drivetrain in a street rod. LS1 with a TSP 228 cam LS2 TB. Dyno tuned last year. Sometimes the car will start fine, sometimes it starts for 1-2 sec then dies. If I let it sit several hrs and try again, it usually starts. The other day it happened cold. Today I took it out for a ride, came home, shut it down, tried to restart it after about 5 min and it did it again. I'm going to upload a video if its not too big. I searched through the forums and found several things to check but they check out ok. My temp sensor is reading properly through the PCM. I have solid fuel pressure throughout the start attempt. I thought maybe flooding due to a bad IAC, but it didn't help to hold the peddle down while starting. Also pulled a couple plugs and they're brown and dry. I did notice that when the key is put in the on position that the IAC whistles and then there's a click. I don't know if this is normal because I never really sat with the key in the on position and listened before. I'll attach a video of that as well. This happened to me one time early last year and never came back. Now I'm getting the car back out after winter and it's happening more often. Not sure what to try next. Its also had to take it to a garage because some days it wont do it. Frustrating! I have no codes. I'm thinking next to change the crank sensor and cam sensor even though I dont have a code. Could it be injectors? How about low voltage to the coils? Which wire would I probe to check this if I unplug the coil packs? I assume it should just have 12V to the coils when cranking.

Looks like my video clips are too large to load. If someone thinks they can help, I can email or text them.

Thanks all!! Mike

 

Forgot to mention. When I let the car sit I turn the battery disconnect off. Maybe something is getting messed up and then functioning properly again after the PCM resets. ?? How long does power have to be off to reset the PCM? Next time this happens I'll disconnect power until the PCM resets then try to start it while its still hot. Not sure if the sitting works because it cools or it resets?

 

Be sure to read my entire entry.

 

Can you start this on a separate thread !!!

 

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So you are saying your car is fixed ??...new key and ignition switch...SUPER !!

 

Yes it starts everytime now. Be sure to get an oem key