Having issues with misfire under load. Full throttle seems ok. Codes 542 and 543 came up. Compression is 130 psi across the board. Cleaned maf, no change. Changed msd coil to new accel coil. No change. 02s new last year, fuel filter is new, 255 pump new last year. Fuel pressure it idle is 34-36, 39-42 with no vac. I checked the timing cover ground and it was loose, tightened wi no change. Car has msd pro billet dist. with Napa pip installed, when cold runs great as soon as it warms up over 180 has a part throttle misfire, very evident when in 4th gear at low rpm. I swapped the oem dist. Which also has new pip back into car, and the misfire is all the time when warm, even at full throttle. Leaning towards tfi, or ccrm, based on the codes pulled, any ideas? Mods as following Bbk cai bbk 75mm tb trickflow street heat iintake no smog, ac or ps evap canister removed msd cap and rotor ffrp wires mac equal shortys mac h pipe flowmaster 10 series mufflers
What about plugs? Stock E7 heads? TFI could be culprit, although this is more common on a Fox since the TFI would get hot being attached to the distributor. The SN had it on the fender, also my experience is when the TFI fails, car does not run. The other obvious thing is firing order, plug wires, and is your MAF stock?
Cleared codes, ran koeo test no codes, ran koer test no codes, balance test ran 3 times all passed. Drove car with maf unplugged and seemed to run better at low rpms,but high rpm s breaking up. Maf has power and ground, but return signal to ECM ground is only 6.0 volts not 12. I pulled ECM out and back pinned 9 pin and its 6 volts ground there too. When unplugging the black connector in front of ECM voltage at ECM pin 9 and at maf is 12 volts. The black connector when plugged back in with key on cycles fuel pump, is this nrmal?
you ever get this fixed? how old is that MSD distributor? changed my distributor out recently and it fixed my misfire issue, exact same symptoms as you described. my PIP sensor in the distributor was very loose and wobbly, should be nice and firm in place. check that out. i bought a Napa brand dizzy for 100 bucks and it works fine.
Still working on it,lol. Put oem distributor back in with new pip still does it. As soon as Temps hit 180 or higher starts m hesitating. Checked both 02 voltages .18-.98 at idle. I am at a loss.
