Random misfire, changed plugs, came back, do i need to change all coils?

Question

2004 Cadillac DeVille DTS 4.9L with a random misfire, changed plugs, came back, do I need to change all coils? won't tell which cylinder

Answer 1

HI there,

This can be a tricky code to locate. If it idles rough, you can take some carb cleaner with the engine running and check for vacuum leaks. If the idle speed increases or smooths out then you have a leak. If not, then next course of action would be to replace the ignition coils to try and eliminate the problem.