Spark knock My car spark knocks when the outside temperature is high and when using 87 octane fuel. Using 89 octane fuel alleviates the problem. The spark knock occurs under moderate load but does not occur under full acceleration. In winter months I do not notice the problem even when using 87 octane fuel.

SOURCE: 1997 Mercury Sable GS

Two possible sensors could be affecting it like the TPS or MAF sensor. The Throttle Position Sensor (TPS) might have a bad spot where the ECM won't get signal properly and causes the RPM to fluctuate

SOURCE: 2001 mercury grand marquis. Engine stutters or

Start car and use a squirt bottle of water to wet the wires and coil, if you see it spark or run rough one or both are bad, repair the wires first as they are more common.

SOURCE: at start up car smokes like crazy but only once in

Sounds like you have a bad valve seal (or maybe several).

Basically there are seals for your valves that keep oil from dripping down into your pistons and smoking like crazy. When these go out, oil drips down when the car sits still for a while.

It's an intermittent problem because not all of your valve seals are bad. Depending on the position of your engine when you turn it off determines whether or not your bad valve seal(s) is going to leak oil into your piston.

I had this problem on one of my first pickup trucks. From everything that people told me, you don't really have to worry about it. It's embarassing, but it's not causing any real problems.

To confirm that this is the case, you could pull your spark plugs. 1 or more (but not all) should be fairly black and even have a little bit of gunk on it (maybe like a bbq grill).

I hope this helps.

SOURCE: I have a 2005 Grand Marquis (under 50,000 miles)

I would be willing to bet it is the catalytic converter! I just had mine repaired and it is covered under the emissions warranty. Hard to believe the Ford dealer didn't know since it is a no brainer for them to get paid!

Ron
Celebration, FL

SOURCE: no spark and no injector pulse on a 92 capri 1.6

When you have both no spark and no injecter pulse its almost always the ignition module. The good thing is you can remove it and bring it to your nearest parts store and most of them will have a tester for those, but I am sure you will find that it is bad.