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Discussion Starter #1
Started today on the way to work. I down shifted coming up the exit ramp and when I stoped it felt like it was idling rough. But I could drive out of the misfire by about 3000RPM. I swapped in a another set of plugs new wires and checked spark at all 4 cylinders all is good.

I am leaning towards an injector going bad or a MAF that needs some help. Any ideas?

I havent checked compression yet but i dont think thats an issue. I did a new head gasket about 7500 miles ago and all was well.

By the way the car has about 45,000 on the clock today.
 

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Does the car rev to ~7000?

Does the car idle? If so, rough, good, etc.?

Do you have a check engine light? If so code P0300-P0304?
300 is random, 301 is Cyl 1, 302 is 2, 303 is 3 and 304 is cylinder 4.

Have you changed your fuel filter lately? I think 15,000 miles is the interval on it.
 

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Discussion Starter #3
Havent done a fuel filter. Car idles like crap. No DTC's stored pending or active. Didnt try to rev to 7k beacuse it wasnt perfectly smooth up top but it was significantly better. Took it to about 5k though
 

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Are you sure it was a misfire? Doesnt that throw a CEL?
 

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A misfire WILL throw a code. When I misfired (even when I couldnt feel it) it threw a code in my face. Ok, how are your plugs gapped? I dont remember the NA gaps (Im turbo with .035) but surely someone knows. What plugs are you using?

Try a fuel filter....its like ~$15 for the part and you can do it with a 7mm socket (and a good extension) and a flat head for the clips. (I work for Jiffy Lube and do em all the time - its a walk in the park!)

FWIW, my misfire code (301) did go away with my new injectors after turbo....but again, it threw codes.

Do the fuel filter, pull the spark plug boots, make sure theres no oil around the pul (mine leaked at the valve cover, down into the spark plugs, and compromised the ground and I had a misfire).

Im just tryin to cover all the bases.

Start with the maint. crap first...fuel filter is your cheapest route at this point. if you cant/ dont want to - Jiffy Lube charges $49.99 (prices may vary) and you'll get a warrantee on it
 

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Another thought....check you intake mnaifold couplers (under the fuel rail, 1.5-2" rubber tube with a clamp on either side). Make sure the coupler isnt letting unmetered air in; it would probably cause a lean code, but still...covering the bases.
 

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Discussion Starter #8
I'm a chrysler tech. Not trying to shoot anyone down. I will swap the Fuel filter never even thought of it. I was just working on it over my lunch. So I was in a hurry and not thinking much.

If its not a misfire I dont know what it is. it runs like crap down low. Like its on 2-3 cylinders so if its not missing I dont know whats goin on. Only thing (other then fuel filter) is maf or injectors/pump. Thanks for the suggestions
 

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Hmmm, ya know what, at 45k my Primary O2 needed replacing. Felt horrible down low but WOT it was fine. I also had a wideband, so I could see the A/F Ratios going all over the place. O2 from Ford is about $88. Dont go to a parts store, it'll be too short - gotta get Motorcraft to get the right one.
 

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Rear doesnt do anything with driveability - it just checks for cat operation, thats all...the primary will definitelyeffect the way your car drives, especially on light throttle/ cruising.

Another thought, do you have a CAI? Did you drive in heavy rain recently? If so, TPS might be hosed. Thats about $16 from ford.

As you can guess, I've had similar issues. A bad TPS will also cause a surge feeling in these cars...

I am yet to replace the MAF. Ive done Primary O2, and TPS as the sensors needed to be replaced due to bad low throttle cruising.
 

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Discussion Starter #12
I dont have a CAI. But my old roommate had an 03 svtf and he had a bunch of TPS problems. So I was also thinking that way as he was saying his would do similar things
 

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TPS or Primary O2 sensor, those are my guesses. TSP is obviously cheaper. ;)

Keep me posted!

..and still, fuel filter wouldn't hurt!
 

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Discussion Starter #14
I'll let you know. I will do a sweep of the TPS tommorow and see if I cant monitor that primary o2
 

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Take the TPS out and on the inside you'll see a metal ring...you'll liekly notice little dots of moisture - if you do water killed it. Im not 100% sure what the voltage range is at idle v. WOT.

Good luck!!
 

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Discussion Starter #16
might me it as I was at the car wash on friday night and it really wasnt driven over the weeked
 

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Yeah, TPS' arent fond of water. Even with having CAI's I only had an issue once and that was during last years hurricane season. My O2 went out early this year....thats just a common maint. part. Wears over time.

I figure I should stock up on em with the octane booster I run and 100oct. at the track.
 

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When my TPS went out, I didnt run bad at all other than the fact it just wanted to rev to redline anytime it wasnt in gear..LOL. I have heard many stories though of the TPS causing similar problems.
 

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Dont just replace parts check them to see if there bad , any Ford Predator will read the TPS and tell you if it is working , find a scan tool

Tom
 
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