iroc7

My 1988 Iroc convertible just started doing this today. The car has 80,000 miles and had been working very good previously.It starts right up when cold but for the first 2 to 3 minutes in runs rough and chugs.After it starts to warm up it runs good and pulls hard thru the gears.Any ideas please...

Duke

I'm assuming it's throwing no codes?

When was the last tune up?

87irocbeast

Your cold start injecter might not be working right. When the engine is cold the cold start injecter adds extra fuel to richen the mixture then shuts off after 2-3 minutes. It might be adding to much.

87irocbeast

also might just be bad gas. If it just started doing it wait and see if it stops after you fill up again. 92 oct. or better.

faded93bird

replace your ecm coolent temp sensor, they are like 10-20 bucks.

iroc7

Thanks guys. It has not done it the last few times I have had it out. I really need to run the car more than I do. If it starts doing it again I will get a friend with a scan tool to check it out. I love that car....

Gord's Green Z28

I'm thinking 3 possible problems.

Battery is low on CCA's. This won't show up with a volt meter. The meter could still show 12.7 volts but the battery could be putting out 300 CCA's. Need to get a load test at a parts store somewhere.

Chip.

ECM.

I had a problem with my ECM. Checking the TPS sensor with my multimeter, it would show 0.54 at idle and 4+ volts at WOT......Yet when it hooked up to a scanner, the scanner was showing 0.9 volts at idle and 1.8 volts at WOT. (ran awful). New ECM and problem solved.

Might want to simply throw a spare chip in it if you have one. Easy way to test it. I had one go bad after running flawlessly for 20 years. Go figure.