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1991 Chevrolet Silverado surging at idle


Topic starter

How's it going scotty. I have a 1991 Chevy silverado with a 5.7 liter tbi and it surges at idle really bad and throws a code 44. I had 2 mechanic shops try and fix it but they didnt. They rebuilt my throttle body, replaced ecm, replaced injectors with brand new injectors not remaned, replaced distributor, replaced coil, plugs, plug wires, rebuilt motor,rebuilt transmission, new fuel pump, all new sensors, no vacuum, leaks no body knows what the hell is going on with this truck, it just wont run right at idle, it runs great when you drive and the code go's away, but as soon as you are in a idle position it idles horribly and sometimes stalls. The mechanic shops told me just get rid of the truck but it has to be something simple I have stuck so much money in this truck I just need it to idle right, what do you think Scotty.

1 Answer

sounds like a text book cases of a vacuum leak.  I know you said it doesn't have one but it sure does sound like it. They can be extremely hard to locate and can take hours of looking. Every single mm of vacuum line, gaskets, seal and hoses have to be inspected. Pretty much you have to check everything. Even a bad valve cover gasket can cause it. Since your car is a 91 we can't use live data to confirm. Easiest way is to smoke test and use break clean or carb cleaner. While doing it also watch rpms for any change. Even with a smoke machine you may not detect the vacuum leak. To me it definitely sounds like a vacuum issue