How do you fix an engine misfire on a 1998 Oldsmobile Intrigue when the plugs wires and coils are good?

Answer 1

On computer controlled engines such as the 3.8L or 3.5L on Intrigues, misfires can happen for any number of reasons. The diagnostics may contain codes that show what's wrong if the unit is read, but these stored codes should also light your "Check Engine" light. You could try having the unit read at Autozone or a dealer, but this may not show anything, especially if the computer itself is bad. When the engine goes to limp-in mode it may seem to be misfiring since all the sensor settings are set to a nominal value. The engine will run, but definitely not smoothly. This type of problem is difficult to diagnose by chat room, I'd take it to a dealer and pay the piper.

ANOTHER ANSWER

I was also told this can also be caused by issues in the fuel system i.e. low fuel pressure, injector issue, etc. Might want to try a new fuel filter (under the body - driver side around the rear driver side door) and some throttle-body cleaner, and also add a can of fuel injector cleaner at your next fill-up.

ALSO - check for vacuum leaks. They can be causing a lean-out condition on your fuel-mix (too much air).

I'm experiencing this very issue right now, with a "Service Engine Soon" light for code indicating cylinder 6 misfire detected. I'll let you all know what it ends up being. Starting w/plug & wire, then fuel system.

UPDATE - I tried the fuel-injector cleaner first w/tank of 93 octane, and ran throttle-body cleaner into the open TB. This did not fix it for me.

I then removed the #6 plug wire and plug. The plug looked OK but had an ENORMOUS gap, so I closed it some and cleaned the plug w/throttle-body cleaner and engine degreaser. Then I FOUND THE ISSUE - plug wire had a cracked casing about mid-way in the wire. Replaced all the plug wires and now - $37 later - it runs sound as a pound again!