Misfires - 2000 Jetta

[scterry]

I need help! It seems that my mechanic can't figure this out.

My car's engine light comes on and reads a code of "misfire". It is always on the same cylinders - 2 & 3. The car may run good for a day and then will start acting up for no reason. However, it seems that in the afternoon is when it happens most frequently - never on the first ride of the day.

Here's what they have done so far:

Replaced Mass Air Flow Meter
Replaced wires & plugs

One shop thought that the Co2 sensor may be damged because I recently blew a head gasket. I had the head checked for leaks, resurfaced and reinstalled. The engine itself runs like a champ until the misfiring begins.

What else could it be - maybe the coil pack...injectors..?????

Thanks a bunch!

Steve

[Doug Tatham]

I suspect the cylinder head repair may not have been quite right and as it heats up and metals expand you're losing compression. The head bolts are torqued in sequence over several steps. They may need a final tightening, it is common to save the last 90 degree turn until after the engine has run 1000 miles. If plug wires for 2 and 3 were switched, it would always misfire and probably not start. The plugs may loose; I think the torque spec is 14 psi (check the spec and tighten accordingly). I recommend you check with the people that reworked your head and see if the head bolts need a final torque. I'd also check the compression with the engine hot. The problem could solve itself over time as well.