It's either an ignition system failure, sensor failure, or fuel system failure.
When you have an ignition system or sensor failure, the computer usually picks up on it, after all, that's what it's designed to do.
With the fuel system, the computer will only detect a "multi cylinder misfire", but won't know what's causing it. This is why I suggested you check the fuel system components.
Having said that, an intermittent failure with the ignition system or sensors won't always set a computer code. But they're easily checked with a capable scanner during a live data test.
Fixing your problem will be a process of elimination, and unfortunately, I can only point you in certain directions based on the information you provide.
Remember this, instead of replacing parts in hopes of fixing your problem, take a logical approach and test each component. This will save you money and time.
Start with the fuel system.
Wednesday, November 24th, 2010 AT 7:21 PM