Hiya folks..
Just to give you a little heads up on a problem I had with my MK2 8V recently. Ever since I had the car (1 month) I have had this annoying misfire whilst travelling down the motorway to and from work. I did the normal things like change the leads dizzie cap, rotor arm etc, but this didn't cure the fault. I was tempted to change the coil, but as it wasn't failing under load I was reluctant. I checked the coil at night for the usual signs of 'blue glow' but nothing was seen.
Well last Friday I was bombing down the motorway as usual and the misfire came back again, something triggered in my mind to dip the clutch, blip the throttle a few times and lift the clutch again. Suddenly the misfire went! Hmm this is strange... Okay about 5 mins later the misfire came back again, so I did the same. Same thing happened and the misfire went. So I knew I could cure the fault by doing this and it only happens at fairly constant speeds. First thoughts were the MAF (Mass Airflow) which might be giving off spurious readings to the ECU and cutting off the injectors, so at lunchtime I took out the airbox and put it on the bench at work. Stripped it down and took off the black cover to the MAF and had a look inside.
The potentiometer seemed okay, and I placed an AVO (moving coil meter) across the tracks and moved the airflow trap. The needle went all over the place, so this was indicative of bad contacts. Therefore I cleaned the tracks and needles with switch cleaner and tested again. It was still moving eratically but no where near as bad as before. There does seem to be some laser cut resistors along the track so it somehow changes the range of resistance when moving from one side of the track to the other. Also it is in a 'bridge' configuration so the sensor in the air filter side of the network also comes into play.
Anyway I cleaned it all up, re-siliconed the black cover back on and put it back in the car.
BINGO!!! No more misfiring and the car is running alot smoother.
Not sure if you folks have come across this problem before, but I thought I would add this to the forum for future reference.
Paul..
