Hey guys been quiet for a long time between log in's, I have struck some trouble with a misfire.
Driving home from work was all good like every other day but last 10km the engine has a started misfiring. once home pulled leads and reconnect one at a time to pin point cylinders at fault which is cyl 1 & 2, can hear spark jumping from lead to plug end on both plugs when disconnected, next step was pull plugs and check spark getting through plugs, yep all good strong blue spark, did a compression test on cyl 1 & 2=210psi all good there, checked injectors=they are functioning correct, disconnect batt and remove J3 chip, reconnect batt and start up running worse so undo last step. Have no vacuum leak that I can detect so I am now puzzled as where to go? could it be fuel filter or crap batch of fuel? travelled 210kms on tank.
Any thing that could be at fault that i'm missing?

cracked dizzy cap........

will be something simple for sure......and the hardest to find....

Cheers

Daz

Did it hesitate randomly or just under acceleration? Does the power also cut out ever so often and idle is crapola?

It could be coil or distributor. Blocked filter also causes hesitation but usually only under load and idles fine.

My car has had issues with cutting out and hesitating every so often. When it does, it is due to my J3 chip playing up. I unplug it, replug it and it works fine besides the idle. Takes about 150-200km before the idle behaves itself, before those kilometers, the car would just stall once I push the clutch in...so I have to heal and toe when stopping at the lights. Car drives fine though, so I hate to drive the thing when I reset the ECU.

Pull the J3 chip out and go for a drive, if the car drives fine, then I think it's the J3 chip...either faulty or the contacts are bad. I have a suspicion that my J3 slowly works itself off (even though it is gaffa taped to the case) due to the stiff suspension and retarded bumpy roads in my neighbourhood.

Did I read that correctly? Getting only 210 kms to a tank? That would be running uber-rich (6-9 AFR). Are you getting noticeable black exhaust smoke? Most common cause of that is a failed MAP sensor or (possibly) leaky vacuum hose to the sensor. But that shouldn't be cylinder-specific.

Maybe there's crud jammed in the injectors, holding them open? Somehow, you are getting too much fuel into your engine. If you swap injectors 1 and 2 with 3 and 4, you can tell if it's the injectors because the problem will move to cylinders 3 and 4.

A failed oxygen sensor can cause it to run rich, but I wouldn't have thought by anything like that much (maybe 10-15%).