91 Firebird 305 TBI sputtering

I have a 91 firebird 305 TBI with about 167,000 miles. I am the original owner. A couple of months ago, I started having this problem. It seems to run OK when first started cold, but as it warms up I can feel it "missing" or hesitating under light acceleration. After about 15 minutes when it is fully warm, it will run very badly, missing and sputtering whether accelerating or idling in gear. After 5 or 10 minutes of this it then improves somewhat, sometimes the problem will go away, or when I have to stop and idle again it may or may not continue. After the weather turns bad in November I don't drive it much, maybe once a week or two. It is in a garage when not being driven. I replaced the fuel filter and ran heet through the gas. I took it to the dealer, they found no obvious problems or computer codes (of course), but replaced the cap and rotor because they said there was some corrosion. This did NOT fix the problem. As you can understand I do not want to throw more money at repairs that do not fix the problem. Any ideas?

Have you checked the fuel pump or pressure?

If the fuel pressure check out have the ICM (ignition control modulu) tested several times

I thought when a fuel pump quit it just quits and does not run. Is this different for an electric fuel pump as opposed to mechanical?

Someone else told me it could be a bad spark plug wire or hairline crack in a spark plug that behaves different at different engine temps. Does this sound likely?

Why would a problem with the ICM not turn up any computer codes?

I thought when a fuel pump quit it just quits and does not run. Is this different for an electric fuel pump as opposed to mechanical?

Someone else told me it could be a bad spark plug wire or hairline crack in a spark plug that behaves different at different engine temps. Does this sound likely?

Not neccessarily saying it's a fuel pump failure, but a pressure check, especially a running check when the problem occurs can eliminate it from the picture.

Cracked plug, it should run like poo at all times.

There are a few ignition components that can cause these symptoms, BUT, anytime I hear "sputters" I tend to lean toward eliminating the fuel system.

Problem found. Bad spark plug wire. Thanks for all the tips.

Problem found. Bad spark plug wire. Thanks for all the tips.

cool beans, love it when it's something 'easy', thanks for the outcome :thumbsup: