Code - P0304, fuel injector?
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From: Arizona
Code - P0304, fuel injector?
I've got a '98 F-150 SC 4X4 with a 4.6L and 115,000 miles on her. In Jan engine started missing and the check engine light came. Over 100K miles, so I changed plugs and wires, fuel filter, and reset the light. Ran great for 3 weeks and then same thing, missing in cylinder 4. Checked the wiring like manual says, good, checked coils, good but swapped them side to side anyway. No change, swapped plug wire on #4, no change. Replaced injector and plug, fixed the problem. A week later, got code P0308, changed injector and fixed the problem. Here we are in Aug, and I've got code P0304 again, I'm missing something in the chain. Anyone have a similar experience or know what I'm not checking? Any help would be appreciated.
Thanks!
Thanks!
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Joined: Dec 2001
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From: Southeast FLA
Can that screen be cleaned once out, or does it require replacement of the injector?
I've got an intermittant miss that goes away with enough good fuel injector cleaner, but comes back again - and gets worse with time until treated again. Yet I get no codes, thus everyone is stumped as to what it could be.
When it does do it, it seems to buck a little harder when under load. I believe it is an injector.
I've got an intermittant miss that goes away with enough good fuel injector cleaner, but comes back again - and gets worse with time until treated again. Yet I get no codes, thus everyone is stumped as to what it could be.
When it does do it, it seems to buck a little harder when under load. I believe it is an injector.
New User
Joined: Jan 2007
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Ive got the same problem in my 97 F-250LD 5.4. I was hauling my 4 wheeler out to the hills today when the truck started missing and my check engine light started flashing. I pulled over and plugged my coder reader in and got p0304 (misfire cylinder 4). When I got home i pulled the coil pack out along with the plugs and injectors. All seem to be in good condition and the 2 prong platinum plugs only have 50K on them. Anyone have any ideas??
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a flashing MIL indacates a catalyst damaging misfire- no spark (unburned fuel goes straight to the cat)
a regular MIL with a code 030X indicates a straight misfire, no fuel (usually), could be no compression too.
believe it or not bad spark plugs do happen. Also try spraying a garden hose on the plug wire and look for any blue sparks that are shorting out. Ignition coils can short out internally due to carbon tracking, and injectors can get clogged. You could clean an injector with carb cleaner or a parts washer, but its a lot of work to remove it and put it back in to test it. Run some sea foam or whatever though the gas tank, make it 2 things of seafoam.
a regular MIL with a code 030X indicates a straight misfire, no fuel (usually), could be no compression too.
believe it or not bad spark plugs do happen. Also try spraying a garden hose on the plug wire and look for any blue sparks that are shorting out. Ignition coils can short out internally due to carbon tracking, and injectors can get clogged. You could clean an injector with carb cleaner or a parts washer, but its a lot of work to remove it and put it back in to test it. Run some sea foam or whatever though the gas tank, make it 2 things of seafoam.
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Joined: Dec 2001
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From: Louisville,Ky.
Check for anti-freeze in the #4 plug pocket. Sometimes the heater hose back there drips into the plug pocket and shorts out the wire. I wouldn't spray a 4.6/5.4L with water, it will surely short out when the water reaches the plug pockets!!!!
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Well im going to replace all the plugs today and see if that help if not ill replace that coil pack. Im also going to check the compression on all the cylinders. I wasnt sure why the light was flashing at first, i had never seen that and it worried me but thanks for letting me know.
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New User
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well i ran a compression check through all the cylinders and #4 read 70 out of 150 psi. I threw some oil down the spark plug hole and checked it again and it got 120 psi, so im sure the rings are gone.
One thing i found to be weird is when i removed the coil off of #5 the hole was filled oil on top of the spark plug.. have no clue how that got there.
One thing i found to be weird is when i removed the coil off of #5 the hole was filled oil on top of the spark plug.. have no clue how that got there.
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98, 4.6L F150
After trying to diagnose a similar problem of missing on my #4 I also found oil on top of my #4 plug. Is the oil causing a short? The injector was partially plugged but changing it didn't help. Earlier the plugs and wires were changed and seemed to help for a while but the problem came back. The coils were swapped but the problem persisted. The top of the engine is clean and dry and the valve cover is not leaking into the well. After cleaning and replacing the plug it is running better today but not sure for how long. I haven't done a compression check yet.
After trying to diagnose a similar problem of missing on my #4 I also found oil on top of my #4 plug. Is the oil causing a short? The injector was partially plugged but changing it didn't help. Earlier the plugs and wires were changed and seemed to help for a while but the problem came back. The coils were swapped but the problem persisted. The top of the engine is clean and dry and the valve cover is not leaking into the well. After cleaning and replacing the plug it is running better today but not sure for how long. I haven't done a compression check yet.
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i also found oil on top of #5 it had no effect though. I noticed that my #4 cylinder coil was out aswell. Replaced that and the truck runs fine now. My low compression is just from all the miles and is gonna need to be overhauld some time soon.
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