4.3 Help

fprefix · July 9, 2004

My truck idles terrible while in gear and blows black carbon smoke. Any ideas or cheap fixes? Please help!

snoman · July 9, 2004

Make, model, year?

Frank S · July 10, 2004

Well,may not be the same but with what little I drove my ZR2,I had the same problem and it was apparently just carbon build up.

You can try and go to a GM service department and get a can of Top Engine Cleaner (liquid,not spray) and follow the instructions to see if it makes a difference.Others have also reported good results with Seafoam which can be bought from an auto parts store.

fprefix · July 10, 2004

My truck is a 1991 Chevy Cheyenne with the 4.3 liter. It has 152,000 miles. A friend of mine said it either sucked a valve or bad valve guide(he thinks). Anything to help would be greatly appreciated. Any temp fix's? I will try seafoam or the top engine cleaner. Thanks everyone!

James

Frank S · July 10, 2004

Well,if it dropped a valve,Seafoam isn't going to do anything.

you may still try it in hopes that it's only carbon build up but if your friend is right,it won't do any good.

Midnight · July 10, 2004

I had an '88 S10, and it was bad for vacuum lines cracking and coming loose. That might be the cause of the bad idling. Or there's a shaft in the throttle body that is bad about wearing and causing a vacuum leak. Either of these problems will give you rough idling and a nasty vibration will sitting still with the truck in gearl.

The valve guides on those engines were pretty notorious for wearing, hopefully, that's what's causing your smoking problem. My S10 had a badly worn out cylinder, I wound up having the block bored .040 over and having the engine rebuilt.

OUMike · July 10, 2004

Hmm..interesting. I have a 94' with the same motor. I'd definatly be interested to hear the cause and your solution to this problem. Keep us posted

fprefix · July 12, 2004

Well, I just tried the Seafoam. It made it idle smoother at higher RPM's, but will now barely run at idle. It smoked like the Seafoam instructions said it would, but now it will not idle stopped and in gear. I will try and blow the rest of the Seafoam out tomorrow. If I pull the valve covers on both heads, will all the rockers move if I sucked a valve? Or is there any visible sign to come to that conclusion? Thanks, James