Engine misses....

[USMC53CHIEF]

Hey guys got a problem, maybe someone else has had this issue.....I have a 98 cobra... I just had the motor out to replace seals, valve covers, water pump, and oil pan. I haven't touched the internals and did not take the heads off. The spark plugs are about 1 1/2 year old. I put the motor back in it last Friday and no problems what-so-ever. I even drove it 1500 miles this weekend from Columbus Ohio to Philly for my drill weekend..... not a single problem, no misses. I drive it back Monday, let the car sit and start it Tuesday and it runs like dog shit. It missed very badly when driving it, but it wouldn't miss all the time. every 10 seconds or so it would "pop" back to normal for a few seconds but then quickly go back away. I replaced the wires last night and still nothing. There happened to be a well known mechanic in auto-zone parking lot that i knew and he said it sounded like a "dead hole" and that i need to run a compression check.. which i am doing right now, so far im gettin 150 psi, but not done yet. I just think im barking up the wrong tree.. i don't think it would go bad overnight... and there's unburnt gas coming out exhaust, so that tells me its gettin fuel... any suggestions? ill be outside in the garage working on this for a while so if you want you can text me a suggestion 419-689-3648....thanks guys

 

[RIO RED SNAKE]

might have bad coil packs..pull the plugs and check the gaps...check all the wires again, maybe one of the coil wires is int he wrong spot..all simple crap it could be...if not the maybe the motor finally had it..how many miles?

 

[USMC53CHIEF]

155,000 miles... strong engine.. most people are shocked when they see it run/perform and then i tell them that. Compression checked good, average of 156.75 psi with the high 1 being 170 psi and the low 1 at 150psi..I had 3 or 4 cylinders at 158psi. there was a questionable plug, which i replaced, it wasn't tight either. i use the Bosch platinum 2's that have a dual tip head, so no gap needed. coil packs are giving spark for all cylinders... after all this, still ran like crap, worse actually. I did notice that the engine did not get any worse/ had no reaction to me disconnecting the maf sensor.. and when i plugged it back in the motor actually bogged down a bit... sometimes idling at 300 rpm. it reacted when i pulled individual fuel injector wires off too so i don't think its them. I'm pretty convinced its electrical, my check engine light is on but the stores are closed so i cant check it, plus i have it on all the time for secondary air injection (smog) and cat-less x pipe. like i said, ran fine all weekend through Monday night then Tues. morning it was really cold and i went to start it and run the heat, i was inside then heard it bog down, hasn't recovered since.

 

[crazycarlo]

well deff keep us updated, also u might wanna think about going back to a conventional plug and leave the platinum 2's alone. Alot of people have had problems with those, I use to run them in my car and they never quite performed right.

Clean ur maf also maybe something got on it.

 

[svtcobralover]

Id make sure your wires in the right place.

 

[USMC53CHIEF]

Ok cleaned the MAF sensor with some contact cleaner, ran nice and smooth after that. got the codes scanned, #5 cylinder missing, maf sensor, iat sensor and catalytic code. the two sensors are from me disconnecting them while the car was running. I also bought motorcraft plugs, even though my bosch's were only year and a half old. My dad was telling me he had a car that had old in the intake tube and it was from a dirty maf sensor, i also had fresh oil on my throttle body... I will see in the coming days whether or not the oil stops building up. Engine runs smooth, nice and strong. Thanks guys!