[y22kc]

I hop in the stang yesterday morning to head to work when it starts idling rough right when I crank it. I always let it warm up about 45 secs or so, so I sit there listening. The idle stays rough, starts shaking the car. The CEL comes on, and I pull out my SCT2 to read em. It gives me P0301, P0303, and P0300 which are all misfire codes. I call the Ford dealership for an appt, but it's not gonna be til Tuesday that they can get to it.

The car is slightly modded with a JLT cai, sct2 tune from Brenspeed, UD pullies, and bassani cat'd xpipe with some bassani axlebacks. I plan to put the stock airbox back on and reflash to stock before bringing it in. It seems like some fouled spark plugs, but I don't use octane booster and always use name brand gas. I know there's a TSB about coil packs rough idle and hesistation which is what I think it may be. I'm scared they gonna try to give me the runaround because of the couple performance mods, but I'll cross that bridge when I get to it. Has anyone experienced this?

[stlwagon]

Originally Posted by y22kc

I hop in the stang yesterday morning to head to work when it starts idling rough right when I crank it. I always let it warm up about 45 secs or so, so I sit there listening. The idle stays rough, starts shaking the car. The CEL comes on, and I pull out my SCT2 to read em. It gives me P0301, P0303, and P0300 which are all misfire codes. I call the Ford dealership for an appt, but it's not gonna be til Tuesday that they can get to it.

The car is slightly modded with a JLT cai, sct2 tune from Brenspeed, UD pullies, and bassani cat'd xpipe with some bassani axlebacks. I plan to put the stock airbox back on and reflash to stock before bringing it in. It seems like some fouled spark plugs, but I don't use octane booster and always use name brand gas. I know there's a TSB about coil packs rough idle and hesistation which is what I think it may be. I'm scared they gonna try to give me the runaround because of the couple performance mods, but I'll cross that bridge when I get to it. Has anyone experienced this?

Did you pull the offending plugs and check for damage or fouling? Did the misfire start after you changed something?

[y22kc]

I didn't change a thing, it was completely random. I didn't pull the plugs because I can't tell visually if they are fouled :-/

[stlwagon]

Originally Posted by y22kc

I didn't change a thing, it was completely random. I didn't pull the plugs because I can't tell visually if they are fouled :-/

Pull a plug from one of the offending cylinders and compare to the plugs depicted here Road Star Clinic - Guide to Reading Spark Plug Performance

[y22kc]

Nice, I'll give that a try. Now how do I determine which cyl is #1 and #3?

[stlwagon]

Originally Posted by y22kc

Nice, I'll give that a try. Now how do I determine which cyl is #1 and #3?

Here you go Ford Firing Orders

[y22kc]

Thanks dude, gonna pull em here now!

[y22kc]

Thanks for your help! It was the plugs, they were fouled out. Weather been crazy lately, I think some condensation accumulated and got in the fuel that caused the fouling. Replaced all 8 for the hell of it, it's running like new again!

[stlwagon]

That's great news! What plug did you replace them with? Autolite HT1s?

[smith2]

I haven't experienced this on idle but when accellerating under partial throttle 70-80% wide open between 4000-5000 rpm mine will sometimes begin to miss and hesitate. I won't be able to maintain my speed. If I shut the car off the wrench light goes off, the car runs like nothing ever happeded to it (until it happens again)
Wish I had something for you, but I don't.
Sorry. If you get any more info re: your specific problem please let me know.
Thanks

[sonny1213]

If the plugs fouled up once … what caused it? I'd be checking the new plugs after a few weeks just to see. If it was foul weather, then my car would be dead or drowned by now.

[stlwagon]

Originally Posted by sonny1213

If the plugs fouled up once … what caused it? I'd be checking the new plugs after a few weeks just to see. If it was foul weather, then my car would be dead or drowned by now.

Yep, depends on what caused the fouling, carbon, fuel, fuel additives.