89turbofox

push rods and valves checked out good. Leak down test was performed on all cylinders. nothing leaked into the cylinder when pressure was applied. cylinder 3 had compression of 130 and all other cylinders were 150-165. Injectors were switched around and misfire still persisted in cylinder 4.

He verified the problem by the heat gun and showing that it is about 160 degrees when all other cylinders are double that.

Im new to this, so I'm just going off what he told me. Since he couldn't find the actual problem (besides knowing cylinder 4 is misfiring) he didn't charge me for all the work trying to find it (which i appreciate). I replaced my spark plugs, wires, and exhaust header gaskets. but problem still going on. I

i wouldn't know what a skip feels like but when i drive the car surges a lot and it wants to hesitate a lot while driving. It is not tuned or chipped.

shooting in the dark here? might take it to another mechanic and cross reference their observations.

mjr46

what size maf and inj's are you running?? I assume the maf is a blow through? at least the on3 kits I've done for people use that type

89turbofox

42 lb injectors 90mm mass air intake spacer. what should i check with these two?

mjr46

what brand maf?? is it cal'd to the 42's?? and or a blow through maf vs draw through??

89turbofox

lightning blow through. don't know if it's cal'd or not.....

thanks for the advice btw man.

mjr46

that in there may lie your issue with the drivibility of the car, it may not actually be misfiring completely, hard to say without being there to feel/hear it with my trained ear/feel, however, iirc lightening mafs are not just bolt on deals when using a stock ecm, I thought the LMAF'S had to have the proper maf transfer functions downloaded to work properly with larger inj's......all "cal'd" mafs do is trick the ecm via alteration in voltage signal sent to ecm into thinking it still has 19 lbs inj's. If your current maf has not had such done, therin may lie the issue......However, I'd pm a member on here named "64bit" he'll tell you what you need to know/do in regards to that.......also did you buy the car this way or did you install the maf??

89turbofox

bought the car like this.. I spoke to my mechanic and he said (ideally) a uncalibrated MAF would not cause a dead skip, furthermore, it will cause other things but from my understanding he made it seem like the uncalibrated MAF was not a ideal causation of a skip.

But maybe i could insist him calibrate the MAF with the injectors and see what happens?

I'm negligent to the head gasket failure assumption, but my mechanic says the gasket could be leaking on the inside and we never know it, which would definitely cause a skip in cyldiner 4.

I wish you could hear it, i can post vids but i doubt the quality will be enough for diagnosis. Mechanic says he can hear it and feel it just by the way the RPMs decline and the way the car surges, etc...

mjr46

if such were the case the compression ring would be blown and definately a compression test would pick such up and often when the compression ring blows it gets combustion into a water jacket or if it were the other way around a loss of coolant.......I think your mech is missing something on one of the tests he has performed if in fact there is a dead misfire on that cylinder which should produce a noticable engine shake at idle and hesitation......hard to say unless I were the one to perform said tests...........has the car ever run right according to previous owner with this current set up? and if so when did this prob occur/ and or what was he doing with the car when the prob reared its head? Also, if it were a head gasket causing a dead misfire, enough coolant would have to enter the cyl to saturate the a/f mixture to not cause combustion and or blow the spark out and if such were the case a compression test would pick it up and or loss of coolant if the blow is on the firing ring, also to verify such, you can pump the cyl full of air with the valves on said cyl closed and if it were blown leave cap off radiator and when you pump the cyl full of compressed air 120-140 psi, you should either see bubbles in the coolant or the level start to rise and overflow out the neck.....see where this is headed.....only other thing is intake gasket for that cyl could be blown or a wiped cam lobe on that cyl, easily verified by watching how far the valves open and close when engine is rotated over.................so if your Mech has skipped a step or overlooked a step, I'd get a second opinion by someone very familiar with the foxbody, not just some run of the mill shop