1991 Chevy Caprice engine speed varies

JOHNBURR

MEMBER
1991 CHEVROLET CAPRICE
V8
2WD
AUTOMATIC
117,000 MILES

This fuel injected engine starts, but spontaneously increases and decreases engine speed, then dies. I have removed the air cleaner, creating no change at all. We got gas at our standard atation 2 days before this and have never experienced the problem before. Do I try Heet, Seafoam, another addative? Buy Injector cleaner and spray it inside the housing, or what? Thank you in advance for any help. Jdb

1 Reply

ERNEST CLARK

MECHANIC
1,730 POSTS

This sounds more like a vacuum leak.

Pop the hood and listen for any hissing noises. Check all of the vacuum lines (There's a lot of them), including the line that goes to your brake booster. Also, a bottle of "Heat" won't hurt.

Do not use any sort of spray inside of your intake. If it gets on the MAF, it could ruin it. And these spray cleaners have been known to eat through seals, causing strange leaks.

Also, injector cleaner that's bought from stores are only snake oil in a bottle. And in fact, most manufacturers recommend AGAINST using these products.

The only "Fuel-injector cleaner" that works (only sometimes), is the kind that must be injected directly into the fuel rail by a pressurized canister at a shop. The problem is, these tend to work too well, and will actually cause your injectors to leak. (Most manufacturers recommend AGAINST using these also)