massred98gt

hey guys new member here. I've been a member of allfordmustangs for awhile and decided to expand my horizons lol.

ok now for the problem. i have a 98 gt that seems to have a severe missfire. Car has a low rpm miss runs ok from 1500-2500 rpms then around 3000 starts to missfire horribly. well atleast i thought i was a missfire, but it doesn't through any codes. it feels like one full bank of cylinders completely shuts down. I've done everything to find this allusive problem. first changed coils and plug wires fixed the problem for 2 days car ran perfect. then like somebody flipped a switch problem came back worse than before. so i checked the fuel pump and pressure everythings fine there. cleaned maf, checked for vacuum leak cars sealed up perfectly, egr seemed ok took the vacuum hose of it went for a drive no different. took the car to my local shop to see if they could find problem no idea. had them clean the injectors and perform some other tests nothing. i've run out of things to check. so now i'm about to check my cats (i have 2/ slp catted x-pipe only 1 yr old) hopefully this cures the problem because if it doesn't i don't have any more ideas

massred98gt

o and this all started after i put in new ported non-pi heads, cams, and pi intake. and i'm positive the timming is correct.

P71Vic

If messing with the coils and plugs fixed it for two days, i would guess that might be the problem area i would look for the problem deeper into the ignition.

blackstallion666

try unbolting the h pipe and see whats happens if it is clogged cats with the pipe hanging down it should run fine. if it still runs like crap i'd be looking at the ignition for the cuase.

massred98gt

hey thanks for your input guys.

ya i removed each cat seperately and went for a drive after each time trying to isolate the cat. but there was no change when i did this. so after the test i thought i would check the ignition out so i went and bout a timming light. checked each wire out to see what the spark looked like. jesus some wires did some crazy things. i tested them all on idle then again while running. some had a constant spark, while others had mostly constant spark but with some blips. a couple wires didn't seem to have spark for a period of time then start up again. i have 9mm wires so would this effect the timing at all. meaning are the wires to thick for the timing light to pick up the spark?

blackstallion666

what type of wires are you using? I had two vehicles come into work with brand new wires installed and they were junk.

massred98gt

ford racing 9mm wires and accell coil packs both only a week old