98 Corvette upgrades

[gdopnt]

Hello, posting for a friend.

Heads, Cam, LS6 manifold up grade problems

This is a 98 corvette. 243 heads, cam and LS6 manifold were installed. Car starts up quickly. Runs good until operating temp. Smells of raw fuel, then the idle oscillates, stumbles and dies if you dont keep it running. Vacuum at start up is 20 when at operating temp and all issues start the vacuum is 4 - 11. The log file shows the MAP sensor is bouncing between 65 and 80. looking for help.

Thanks, Sam

[5FDP]

Needs to be tuned, that's the best way to say it.

Look at those fuel trims, it's yanking back fuel like crazy. The engine has had so much changes to airflow that all the airflow tables are now wrong and it's doing it's best to try and let it run. The VE and MAF need lots of adjustments.

[gdopnt]

5FDP,

Thank you for the reply and Sorry for the questions but from my info gathering, they help me understand more. I was told this model year computer has limitations to programming? Yanking back fuel is why negative numbers in the trims. What would make it change from fair running to bad at operating temp? I understand VE and MAF and will now be looking closer. My label says potential tuner, yes. I've been reading and reading and using this as a next step program. The local tuner told the owner he wouldn't tune this car because of the model year computer. Would your abilities be able to support that?

Thanks, sam

[5FDP]

From what I've read the 98 computer and maybe 99's aren't the "best" for tuning, the 00-01+ have better operating systems. I've never tuned a 98 before. It can still be done but just has more steps or other tables you have to deal with, many they went away with on the new computers.


It runs fine while cold because it's in open loop, once the temps come up and it switches to closed loop it will start trying to correct the fueling and make it run bad because the tune is far off.