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Old 09-25-2011, 06:15 PM   #1
Bran Diezel
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Default Ford Techs? 2004 F150 4.6 w/ rough idle

The truck has 140k and came into the shop with stock plugs. Codes were random misfire, cyl 5 misfire, cyl 1 misfire. I swap the plugs because it needed them of course. Still runs rough. I put coil packs on 1 & 5. Light goes out for misfire but then I have Coil Driver A malfunction code. I rewire the grounds on 1 & 5 and I get the light to stay off for that code.

So now I have a light misfire maybe because of fuel or timing. The truck feels alot like a new 6.0 vortec max feels. While idling feels smooth and then a tremor goes the body. No misfires under load. You can really feel the shake when you test drive it and let off the gas and coast without hitting the brakes.

Its been a year or 2 since a fuel filter. I told the guy for $15 it won't hurt and I'm sure it needs it. I can hear all the injectors with my stethoscope and they seem fine. It may need a fuel injection flush. I don't throw parts at cars, I did have to leave 1 new coil pack on even after rewiring the drivers from the pcm.

I read a TSB on the CKP, I am gonna try to clean the terminals on it.

Like I said I am thinking fuel or timing but if anyone can steer me where to next I would be much obliged. I wish I had a scope to check the injectors and coil packs but no luck there.
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Old 09-25-2011, 06:40 PM   #2
scofo
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Location: Northshore of Lake Travis. Marble Falls, Texas.
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Default Re: Ford Techs? 2004 F150 4.6 w/ rough idle

At Ford, we'd get these in the repair side under warranty for running rough, spend time looking it over for rough idle, only to find out "Quick Lane" just changed the oil the day before. Pull the dipstick out to find way overfull on oil.

Who do you think paid for that diagnosis and repair? Yep the flat rate Certified tech got to find it and fix it. Customer doesn't pay, he shouldn't it's under ford coverage. Ford? Nope they aint gonna pay either. Spend fifteen minutes explaining why you should be paid to service manager, nope can't afford anymore lost time. Thanks flat rate tech you saved the day again for nothing.
Bitter, yea, tired of fixing hourly guys screw ups.

Auto repair maybe priced like a commodity buy it sure as hell aint.

Sorry OP kinda lost it thinking of a few rough idling mod motors.
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Old 09-25-2011, 06:52 PM   #3
Stick
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Default Re: Ford Techs? 2004 F150 4.6 w/ rough idle

You'll never find the problem just sitting there in the bay, so take the vehicle for a good test drive to find the problem.
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Old 09-25-2011, 10:13 PM   #4
bgott
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Default Re: Ford Techs? 2004 F150 4.6 w/ rough idle

Get one of those spark testers that are adjustable. Go to the easiest coil on the engine. Unscrew the tester to 30 KV. A Ford coil should put out at least 18 KV or so, I've found that 30 KV keeps me out of comeback land. A coil just blowing sparks into the breeze is stressed less than one fighting cylinder pressure. Remove that easy coil and hook it up on the coil tester. Start the engine and watch the spark. If it won't maintain a 30 KV spark, replace it. If it does, remove a coil from another cylinder and replace it with the coil you just tested. Go through and test all the coils. Now, you did replace all the boots when you did the plugs, didn't you? The spark is going to find the easiest way to ground, if the plug was shot the spark more than likely blew through the boot. It has also been known to run up the fouled plug and go to ground through the primary wiring to the computer, usually if it does that it is fairly easy to diagnose because the computer will not fire the plug at all. If this doesn't fix it it's time to move on to other things, a bad coil or two and bad boots is the most logical and the easiest thing to fix.
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