Whats up everybody, kinda new here. Iv browsed pages and pages and pages on this topic and just cant find what im lookin for. I have a 2000 seville sls with 86000 miles. I got it in 06 with 54000 miles. It has ran great til about 6 months ago. It started runnin rougher and rougher, check engine light came on and now its bad. The engine shakes quite a bit causing the whole car to shake, during idle, accelerating and any other time. The exhaust is also making a constant puff puff puff puff puff puff sound. After a scan, i unveiled a 4th cylinder missfire and something about a mass air flow sensor. The car has been parked for about three months but prior to parking it i changed the plugs, and the old ones really werent all that bad. There was also some oil in a few of the plug wells and on the rubber boots, which are in good condition. I pulled the plugs yesterday which only have probly 5 miles on them, to find that all of them were blackended except for numbers 2 and 4. They were like brand new. Im really lookin for a easy way to fix this issue. Thats not going to cause me an arm and a leg. What could be the cause, the cassette module part, cat converter? Im worried this is going to cost more than I owe on it and its gonna sit in my garage for another year.. Any help would be greately appreciated, i think i included everything.

 

codes ? Caddy's are always cheap to fix; it is possible you need cassette. Codes may indicate you don't.