Thread: Rough idle

This car has like a million miles on it but still a great little get around town car for the kid. Just started getting a P0300 code (Mult. misfire). Did a diagnostic long term fuel trim is -12 but when going down the freeway and take my foot off the gas it goes to like -27. The short term fuel trim is fine running from -3 to +3 on both banks. I don't think it is a fuel problem going to put a gauge on it later and check pressure at fuel rail. Question should my Long Term Fuel Trim adjust that quickly? Also going to start checking plugs and coil packs. Did a vac check (break cleaner) and didn't notice any change anywhere and cant hear a hiss anywhere. Just wondering if I'm on the right track. I know I should check compression but don't have a gauge for that yet. Here I come Harbor Freight. Thanks for any thoughts.

When was the last time plugs and wires were changed? If recent, you didn't install platinum plugs did you? These cars eat plats. Go with stock iridiums or copper. Check to be sure the plug wires are in the correct order as these cars will run quite well with a few wires crossed believe it or not.

When I tried to pull a plug wire to check plug it fell apart. Replaced plugs and wires running great.