Hi all, I have a 96 wrx with the following mods: FMIC, 440s, 3 bar map sensor, induction kit, DV and esl "chip" running mafless,although the mac is still fitted. The car hs developed an intermittent misfire at idle and low revs. Officers aftergiving itsomebeans and will still boost to 20psi with no missfire. I have fitted a newfuel filter and cleaned the idle control valve. But still this strange missfire any clues on what to check next??

Forgot to saythat it only seems to happen when the car/weather is hot, not overly hot but the oil temp is showing around 86degrees.

Thanks

 

hair line crack in a coil pack ????? plug failing????

 

The car has a new set of plugs and coilpacks but I will check them all. My problem is that there is no misfire at full throttle and 20 psi of boost - this is normaly where plugs and coilpacks fail. My problem is that the missfire is at idle and light throttle.

 

You may have some interference issues but these would normally manifest themselves at higher revs and boost.
Check your cam and crank sensors. Sometimes the cam sensor can touch on the cam lobe and this causes a misfire. Pull out both cam and crank sensors and see if there is any bright patch on them indicating a touching.
Other than that ask whoever mapped the car to put their laptop on and see what they can find.

 

I will Check them next weekend as I am away - the crank sensor is sort of near the alternator but where is the cam sensor?

 

As you face the engine the cam sensor is on the end of the cam shaft on the right hand bank close to the oil filler tube but on top of the engine itself behind the black plastic cover. It looks like a crank sensor and is held in position with a 10mm set screw.
Look and see if there is a bright rubbing mark on the surface of the sensor.

 

OK thanks Harvey, if there is rubbing does that not indicate that either the cam or crank has slight movement? Or just that a sensor has moved causing the rubbing and a new sensor is required?

 

I wouldn't like to say without careful investigation but spacing the cam sensor away from the mounting point by a small amount/thin gasket/washer does the trick.