1998 CSVT 2.5 HO...

[Joe M]

Misfires/Backfires under 3k. Sometimes misfiring above 3k when WOT.
Running EXTREMLY rich.

Cleaned the MAF No luck.

Unplug MAF while car is running. No change.
Start car with MAF unplugged No change.

Cant find any vacume leaks.

New plugs. (Bosch Platinum's) Gapped to 48 (stock 54) Old plugs were gapped @ 52 and Misfired/bakfired and would Stall out at a stop sign.


Car also doesnt start right up when warm, but does when its cold.

[RyanM]

first mistake was the new plugs you installed ,bosch plugs suck ass and cause misfire cases

[loads]

Coil pack bad? Does it do worse when you're working it?

[Chrm97PI]

put stock motorcraft plugs in, if that doesnt do it. probably a stuck open egr or stuck iac. check to see if there are codes and monitor cylinders for a missfire and go from there

[Joe M]

Thats just it.
The only code its throwing is Misfire on cyl 1.
Putting the bosch's in made it BETTER!!
I was thinking possibly the EGR, but, with no code's throwing.

[mg72]

Wouldn't that indicate a bad coil pack? If that cyl wasn't firing, the o2 would read really rich.

[Joe M]

It fires, but not at lower RPMS. Too much fuel is being dumped.
I know theres a vacume leak, i just have not been able to find it.

[sport the war]

start spraying around with carb cleaner with a cold engine, it starts idling up keep spraying where you were and pin point it down

[Joe M]

start spraying around with carb cleaner with a cold engine, it starts idling up keep spraying where you were and pin point it down

Thats def part of my next step, I just didin't know if there were other suggestions out there

[OrangeCrush 86]

Sounds like it's stuck in cold/warm up mode? Thus in open loop. That is why unplugging maf doesn't change anything and it's running rich. Long shot but it's cheap to replace the temp sensor the computer reads.

Not sure though as usually this causes high idle and bad gas mileage, just a thought.

[Joe M]

Gas mileage isnt bad.(24ish)
Idle is fine. idles up and down fine, but when kicking the throttole open under 4k rpms it will stumble and buck for a couple seconds until the timing catches up and then fires just fine.

[2 beer]

check compression

[Joe M]

check compression

Havent done that, i dont think it needs to be done though.

its just running really rich, some reason the ecu is dumping too much fuel.

[2 beer]

Havent done that, i dont think it needs to be done though.

its just running really rich, some reason the ecu is dumping too much fuel.

ok. . . . .

[Joe M]

Well Fuel Issue Solved Via New Fuel Filter.

Then the motor went boom. Rod Bearing Went.