: Is my car misfiring?



cadillac6
06-16-04, 08:33 PM
This only seems to happen on long trips I take. I'll be driving and I get a slight jolt. I look to the road to see if its something im running over but no. It does this every so often. I know it is a broad ? but does anyone seem to know? has this ever happened to you? by the way it is a 97 deville concours with 94,000 on it. :bonkers:

Aurora By Olds
06-16-04, 08:38 PM
I had a slight miss in my '95 for a while, and it went away with a fuel filter change.
How long has it been since you've had a tuneup? Plugs/wires/fuel filter/air filter/etc.? It may be due.

cadillacstars
06-16-04, 11:48 PM
remove your engine cover and spray liquid ammonia on your plug wires, listen, feel for the misfire to occur. Ammonia is a substitute (same thing) for a professional product made by Wynn's called hi-volt used to find ignition wire faults. if that yields nothing label and disconnect all of your ignition wires at the coil packs exposing the bare towers. stand back and have a buddy crank the engine over look at the spark from the towers they should be sparking between each other. If you see any spark jumping down to the base of the coil, that coil pack has failed and it should be replaced.

cadillac6
06-20-04, 12:16 PM
My caddy has never had a tuneup its first one is due in 7,000 miles. That should solve the problem. I added a fuel injector cleaner and the problem went away. Should this happen if I added that?

dloch
06-21-04, 09:46 AM
This only seems to happen on long trips I take. I'll be driving and I get a slight jolt. I look to the road to see if its something im running over but no. It does this every so often. I know it is a broad ? but does anyone seem to know? has this ever happened to you? by the way it is a 97 deville concours with 94,000 on it. :bonkers:Mine does the same thing. I attribute it to the AC compressor kicking in and out not a miss. If there was a miss problem I would think the PCM would kick a code.. mine did when I was having head gasket problems. With the new motor, AC compressor along with new plug wires and plugs it still has the same buck from time to time when running at a steady RPM or under very light acceleration.. again which I believe is the compressor.

Maybe Bbob can jump in on this one.

BeelzeBob
06-21-04, 11:35 PM
My caddy has never had a tuneup its first one is due in 7,000 miles. That should solve the problem. I added a fuel injector cleaner and the problem went away. Should this happen if I added that?
If it is running fine then leave it alone. There isn't really anything to "tune up". The plugs and wires can easily last way over 100K.

Just change the coolant occasionally and the oil according to the oil life monitor.

For tuneup, about the only thing to do is to change the serpentine belt and the water pump drive belt (at 100k they are due and don't owe you a dime anymore....). Clean the throttle body bore of deposits to prevent any idle speed control problems or sticky feeling throttle. Leave the rest alone.

Maybe you got lucky with the injector cleaner.... Possibly there was some debris or deposits on an injector causing an occasional misfire that you could feel that the cleaner took care of. Rare..but could happen that way.

Don't make a habit of the injector cleaner or fuel system cleaners as the harsh solvents can damage the electric fuel pump in the tank.

Your car has the OBD2 system that includes an engine misfire diagnostic. If you were getting a regular misfire the onboard diagnostics would detect it and turn on the service engine light. That diagnostic code is pretty robust so I would doubt that you are having a misfire that is very repetitive. A stray, random misfire would not trip the diagnostic as it takes a steady, repetitive misfire to trip it.