P0303 Misfire
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P0303 Misfire
1998 Ford F150 4.6L
Check engine light came on and the engine is misfiring. DTC read P0303 (Cylinder #3). Replaced the spark plug wire and plug and still have the same problem/code. Noticed on the old spark plug wire that rust was on the boot, which is consistent with water/coolant leaking into the cylinder. I have read that is a common problem with these trucks! I'm wondering if the coil pack should be replaced next? Also, next to each spark plug is a wiring harness connected to something attached to the valve cover and fuel line...what is this part called? Could it have anything to do with the misfire? Is this a "Coil on Plug" or "Coil over Plug"???
Check engine light came on and the engine is misfiring. DTC read P0303 (Cylinder #3). Replaced the spark plug wire and plug and still have the same problem/code. Noticed on the old spark plug wire that rust was on the boot, which is consistent with water/coolant leaking into the cylinder. I have read that is a common problem with these trucks! I'm wondering if the coil pack should be replaced next? Also, next to each spark plug is a wiring harness connected to something attached to the valve cover and fuel line...what is this part called? Could it have anything to do with the misfire? Is this a "Coil on Plug" or "Coil over Plug"???
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The COP is the coil/wire/boot all in one. allthere should be is the wires which operate the cop. So what plug wire did you replace? before the cop there was two coil packs that ran four cylinders apiece. the plug wire ran from the coil pac to the spark plug. take and suck up all the water in the spark plug hole, it will cause the same symptom even though you put new parts. So what do you have cops or coil pacs?
Lance
Lance
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I've figured out that I have coil packs...I thought the fuel injector plugs were COP's (I'm not a mechanic by any means). Anyways, we replaced the #3 spark plug wire and the problem continued. We're thinking it is possibly the coil pack...? I had installed a prestone coolant flush kit on the heater tubing, which is where I think the coolant has been leaking into the #3 cylinder. Do you think I'm correct regarding the coil pack being the problem? What else should we check? BTW, the vehicle recently had a tune-up by a mechanic and the spark plugs were changed. We checked the plugs and they are fine, but is it possible that the mechanic mixed up the spark plug wires and only one cylinder is misfiring or would two cylinders be misfiring if this was the case?
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From: Southwestern Pa.
Cops were used only on the 5.4 in 98 if I remeber correctly.
What actually is the problem? Do you have a miss? Is it constant? Are there any other driveabilty issues?
If the only problem is the CEL,Did you have it reset since you replaced the wire? If the code was not cleared but the problem was solved it will take a while for the light to go out. Either have the codes cleared with a scanner or disconnect the battery for a bit. Then see if it comes back.
If you want to check the coil pack there are specs for resistance and such. I would swap the coil packs from side to side and see if the problem then goes to a different cylinder. If the plug wires were installed incorrectly you would see and feel a dramaticaly erratic (miss, backfire,etc) running engine.
What actually is the problem? Do you have a miss? Is it constant? Are there any other driveabilty issues?
If the only problem is the CEL,Did you have it reset since you replaced the wire? If the code was not cleared but the problem was solved it will take a while for the light to go out. Either have the codes cleared with a scanner or disconnect the battery for a bit. Then see if it comes back.
If you want to check the coil pack there are specs for resistance and such. I would swap the coil packs from side to side and see if the problem then goes to a different cylinder. If the plug wires were installed incorrectly you would see and feel a dramaticaly erratic (miss, backfire,etc) running engine.
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I did replace the plug/wire and that didn't correct the problem. Would mixing up the plug wires trigger multiple misfire DTC's or at least a random misfire DTC? The engine is misfiring, but only shows one DTC for the #3 cylinder misfire. Is the next step gonna be to replace the coil pack?
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From: Southwestern Pa.
Plug wire mixup would set different codes. Check this link for a list of causes.
http://www.obd-codes.com/trouble_codes/generic/p0303-cylinder-3-misfire-detected.php
Swap the two coils around and see if the codes goes to the other side. If it does it is a safe bet the coil is bad. Autozone will test it 4 free.
http://www1.autozone.com/in_our_stores/free_testing.htm
http://www.obd-codes.com/trouble_codes/generic/p0303-cylinder-3-misfire-detected.php
Swap the two coils around and see if the codes goes to the other side. If it does it is a safe bet the coil is bad. Autozone will test it 4 free.
http://www1.autozone.com/in_our_stores/free_testing.htm
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We replaced the coil pack today and the DTC and misfire/rough idle is still present. So now we have replaced the spark plug wire/boot and coil pack. If it's a faulty fuel injector, would it cause a rough idle? How do you test a fuel injector? What else could it be?
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I have a tool for testing stuck injectors, here is how it works, you disconnect the trk wiring from the injector and plug the tool in then turn it on what it does is send a signal to open and close the injector, 1 time or three times or 6 times. when you set it you listen for the clicking the injector makes when it opens and closes. If you here this then the injecter is not stuck closed or open. I don't know any other way of testing it with out the device may be autozone or advance will rent it?? UNless you remove it and exchange it anothe injectors and see if the misfie changes from one cylinder to another.
Lance
Lance
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Same problem
OK i pulled 6 codes out of this thing yesterday one for bank 1 being lean, 2 coil faults and 3 missfires. 0171 was caused by the fuel pump, determined by it not holding residual pressure meaning check valve in pump was shot, dropped tank and replaced it......... 0171 went away, then was left with the coil faults which were due to the same thing you are talking about........the rust and other nasty crap on the coil boots, it is rain water that can somehow get past the seals at the top, but is trapped and cant boil and steam and evaporate out it just lays there and grounds the out the juice to your plugs ....... what i did was took #2 and #3 out ONE AT A TIME and pulled the spark plug and discontected the plug to the injector, started it up and let the compression clean out the plug wells it sounded some what like a steam engine lol...... put the plug back in cleaned up the boots, MAKE SURE A THIN LAYER OF DILECTRIC GREASE GOES ON THAT SPRING INSIDE THE BOOT, and put her back together runs fine now.
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