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Hi All,
I have an ongoing saga with a misfire on my 2.0i (same as 2.3i), which I'd like to bounce off you all. It misfires at idle and accelerating from rest. Cruise is fine. Good running while cold.
Replaced so far:
spark plugs
dizzy cap and rotor
Throttle Position sensor.
The plugs, cap and rotor were done by my mech when he was looking into the misfire. It temporarily fixed it, until the next time I drove.
The TPS seemed to fix it for a week. I was getting the CEL code
73 - Short adaptation time
and 51 TPS. I tested the TPS, it seemed okay, but my suspicion was on it for several reasons (when I "cleaned" it with WD40, things improved for a day or so)
The new TPS made no difference for about a day, then I got good running for a week.
At this point I was fiddling under the bonnet and messed with the dizzy. I've since found out that I must have caused the rotor to hit the electrodes, as the rotor key was broken, and I think this caused the rotor to slip, and not be in the right place for the spark at each point.
I've reset the position for now, and things are better, not perfect.
Now the wierd stuff.
1) I checked the MAF, instant responses to throttle. However, when I disconnect it, the misfire stops [autobox stops shiting though :-( ]
2) Checked the O2 sensor. Ditto. I can see it cycle quickly, and see it drop when the misfire happens (excess O2 in the exhaust)
3) Used a propane wash as well as visual inspection. Can find no remaining air leaks.
4) Good sparks, good resistances measured at the primary and secondary windings of the coil.
I've learned a heck of a lot about the Motronic system in this time, and I'm getting an OBDII diag kit to help in future.
My previous theory (before finding the broken rotor key) was that the MAF was faulty, and was causing a lean condition. Richer mixtures during cold running and accelleration made it run fine.
I now believe that the bad rotor causes intermittant bad spark (why intermittant though?) I guess a richer mixture allows a weaker spark to light off the charge.
Really, I can find nothing else wrong with the engine/ECU anywhere. All grounds look good that I can find, all sensors seem to be working fine (can't reach the coolant temp sensor though). Either the car runs perfectly, or it's misfiring like a banger.
Can anyone share any theories, or care to comment on my logic?
Many thanks
Jon
posted by 149.117.2...
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