Problem Description and Possible Solution
Illumination of the Check Engine Light may be the result of a loose or worn gas cap.
Problem DataRepairPal Verified
Average mileage: 95,288 (47,000–200,000)
38 people reported this problem
"service engine soon" code-303 (missfire on no three cylinder)- light keeps comeing on and after I drive it for a few days it goes off then the same again in a few days. I've changed vaccum line;s under the hood. putnew spark plugs & wireing, new coil, & new GM gas cap,- the only thing I haven't checked is the vaccum lines to canister and canister
check engine lights comes on. Vacuum trouble with gas cap. Changed three times. still can not open gas cap, sometimes I have to shut off car, and wait four hours until vacuum is reduced to open gas cap. ( All gas caps purchased in Auto parts store, after checking book for the correct cap. Still having problems. Two caps had to be broken off to finally get them off.
Service engine light came on at 204,000 miles. Mechanic inspected vehicle and discovered leaky seal on gas cap. Since it comes on intermittently, I have not
replaced it yet.