Hot Start Problem

[vetteconvert2]

I have a problem keeping the engine running with a hot start. I've posted the problem before and received quite a bit of advise. Shared it with the tuner to no avail. He suggested it might be low voltage from the battery, so I replaced the battery. Same problem. Basically here's the situation. 2004 6m with approx. 6,000 miles. Added Blackwing, 228/232 cam, stiffer valve springs, ceramic headers, and zo6 exhaust. Car was tuned and runs great, and performance is fantastic. Cold starting the idle very consistent at about 950, and runs very well with no hesitation. The fun (embarassment) starts when I stop for dinner, or drop of a video of at blockbuster (just examples). Upon starting the car when still hot, the rpms will drop and the car will quit. I don't give it any gas because I hope it will stay running. I'm usually wrong. Then I need to hold the peddle a bit to keep it running on the restart. If it returns to normal idle upon the restart, then I can drive it normally with no further problems. The tuner and mechanic are presently at a loss but are willing to take the time to identify the problem. I'm looking for ideas. If this is normal, and I need to live with it, then so be it. It just seems like a simple thing to remedy.

[78Vette-SA]

It's not normal and I've seen it several times.

I assume it started when you installed the cam. Assuming that to be the case, take it back to basics.

Is the throttle body drilled? If not, and although the car can be tuned without it by controlling the MAF Airflow through the computer, it's much easier to drill it. And make sure the MAF is clean.

If you see the post to TSDuke I went through what I do to get a car to idle with a cam installed. His problem was causing MAF readings and timing to go all over the place. Same principles apply. I'd reload your original/stock tune and start over.

I'd guess you need to work on the VE Table in the low RPM range. I'd reduce VE in teh under 4000rpm range by multiplying those columns by .95 then reload and test. You may need to do this a couple of times.

Also, check for vacuum leaks. I take the fuel rail covers off and while idling (cold works as well) spray starter fluid all around the intake and hoses. If the engine races/surges, you've got a leak.

Lastly, back timing below 4000rpm in 2 degree increments to a max of about 6 to see if that has any affect.

Do one thing at a time and test it. PUt a scanner on it and capture data and see what's going on with.

Others may have different techniques to get to the bottom and tune a cam car. Everytime I do it, I learn something new.

http://forums.corvetteforum.com/show...13&forum_id=91

[vetteconvert2]

Thanks. I'll check to see if the throttle body was drilled. I will also remove the blackwing to see if it and the MAF are claen. As I mentioned, I only have a problem when restarting when it's hot. It even occurs if say I arrive home, shut it down, and restart. In the old days, I would compare the problem to restaring the car when hot with the choke on. With this car, it's almost as if the computer doesn't remember that the car is already warmed up, and may not be sending the correct air/fule mixture.

This forum is great.