I've read a lot of posts concerning the check engine light and a missing/shuddering engine with the 4.6L. I've got '98 F-150 and I had this problem last April and went through a whole troubleshooting marathon with it. When the light first came on I took it to a shop and had it scanned. Code 0304, cylinder missfire. Okay, it's got 85K miles, had them reset the light and stopped on the way home to pick up plugs and wires. Changed them out and all was good for about 3 weeks. Cleaned the throttle body. Light back on, same cylinder. Thought maybe it was a bad wire, so I swapped #4 with #6 or 7 (can't remember), no change. So, I though I'd be smart and swap the coils, no change. Changed the fuel filter and the #4 fuel injector. Stopped for about a week this time, then same result. Bought a fuel pressure gage and a scanner. Pressure good, but changed the regulaor anyway. Pulled the plug again, it was in bad shape, I'm assuming that by the time I changed the injector it had overheated and been burned and the ceramic might have been cracked. All was good for about two months, bam, code 0308. Changed injector and plug, problem fixed. Truck has been running great since.

125K as of today and it's starting all over again, light's on, code 0304. WTF! Gonna pull the plug and check it out after work tonight because #4 is so much fun to get at. Does anyone know the direction of the fuel plumbing, it looks like #4 is either first or last in the line, can't get a good look at the lines at the back by the firewall. Maybe it's a partial fuel rail clog, but I'm thinking the pressure would be high if thats the case. My gas mileage hasn't gone down and power/performance is good so I'm not leaning towards a valve problem. I don't know, has anyone else gotten this far into anything like this?

Thanks, hope this helps someone in similar situation, but at the same time I can't see replacing an injector and plug every 40,000 mile! Gotta be missing something somewhere??? Sure as hell don't want to take it to a dealer so they can charge me big $$$.

Crush
Semper Fi!

 

I agree with the dealer issue. Most won't do any more than you already have.

I've seen so much written on misfires that have no real explaination I haven't got a clue but... Doubt it's related to the valves or the fuel rails. Either one of these would be a constant. Valves don't heal and clogs rarely just go away. Wouldn't be able to get the light to stay off for more than 100 miles at a time.

I chased a miss for about 4 months, then just switched the wires and it's been fine for the last 8k. Who knows. I'm starting to think these misses are suspect.

At this point I'd just go with another OEM plug, wire and COP.

Let us know how it goes.

 

Thanks for the input, and yeah I've gathered from reading all the other posts that there seems to be no rhyme or reason to some of these codes. Although the COP engines seem to be more involved than not. My 4.6 is not a COP engine so I haven't had to deal with that issue, I only have two coils that cost $50+ dollars apiece so it could be worse. Didn't feel like messing with it tonight after work, so it's on hold until the morning. I will follow up with some plug characteristics after it's pulled. I still feel like I'm treating the symptom and not the problem though, and that nagging feeling like I'm missing something obvious. Murphy is laughing at me, I can hear him...

Crush
Semper Fi!

 

Does it feel like it's misfiring again? I believe that on your year of truck there was an updated flash for the PCM to make the misfire monitor less sensitive. Bascially it let's it misfire a bit longer before it turns on the light to prevent the light coming on when there really isn't a problem. To find out for sure your dealer would have to try to reprogram the PCM and their scan tool will tell them if there is an update or not.
Have you checked for vacuum leaks?
Any sign of water getting into the spark plug hole?
What brand of plugs and wires did you use?

 

I would recomend Ford OEM plugs and wires, some aftermarket stuff is a failure waiting to happen. From expearence I speek.

Dave P

 

Well... I have good news and bad news. The good news is that my check engine light and cylinder misfire is not related to a fuel injector problem. So that problem is still solved, the issue however is a fouled plug. Now for the bad news, it's oil fouled. I'm sure that Murphy, although know for his games, didn't let the ring gaps magically line up just long enough to foul the plug, which unfortunately means it's time for rings. I checked the dipstick and didn't find any coolant. Went ahead and replaced the plug while I figure out where I'm going to get the funds to fix her. Time for a Lightning Crate Engine! Yeah right, that's not going to happen. Hopefully it won't rain much in the next couple of months and she can sit for awhile, I hate riding in the rain!

Crush
Semper Fi!

 

Had another thought after logging off, so went for a drive to see if maybe it could be attributed to a leaking valve guide seal. No such luck, I got about two blocks on the new plug before I felt the shudder from a misfire. Something a little strange though, not seeing any white smoke in the exhaust from burning oil? Does the computer just shut down the injector once the misfire is detected? Anybody seen this before? Racerguy, you ever run across this?

Crush
Semper Fi!

 

Crush,


Sorry to hear the bad news but thanks for posting what you found. Still sounds odd to me that the rings could be bad. I'd be more inclined to beleive what was written above regarding the valve seals.
Anyway good luck with the fix.

 

You got your next post in before I finished my last.

You wouldn't get white smoke from oil you'd see blue. White would indicate a coolant leak into a cyclinder.

 

Your right, but white or blue, exhaust is free of any sign of a problem. Whether driving or parked and revving the engine. Not sure what to think right now. Won't really know until the heads come off. Believe me I'd love to get out of this cheap by replacing a worn out spring and a valve guide seal, especially with only 125,000 miles, but.... Thanks Greasy!

Crush
Semper Fi!

 

I guess my CRS (Can't Remember ****) is acting up, went back and viewed my original post on the P0304 code. It wasn't April and 85, 000 miles, it was August and 115,000 miles. So it's only been 10,000 miles, regardless, it's still not an injector issue.

Crush
Semper Fi!

 

I am having the same basic problems ruff idle and driving caused by misfire, with no smoke in the exhaust, with my 97 4.6L. what color would the coolant appear to be if I were having problems with oil in the coolant. My truck will run fine for 2-3 days at a time and then misfire in both banks one and two. I have replaced plugs, coil wires coil packs, fuel filter basically all but the injectors. I get codes 0304, 0306, ans 0301. Any sensors that could be causng this. Could it be a malfunction of the PCM

 

wjbv5

Still learning how the PCM and sensors work together in all the various stituations so can't help much there but, coolent in the oil I've seen a few times. If there is alot of coolent and the engine has been run right before you check it the oil will look muddy not clear. If the engine hasn't run you may see beads of water in the oil, on the dipstick.

 

WJBV5,
You see what I went through on my '98. Or you can go back and read the original thread posted on 17 Aug 05. I dealt with this over and over between Jan and Aug, finally changed the injectors and it fixed the problem. I know they're a little pricey but it beats lugging down the road. Some places advertise they can clean your injectors but I don't know anyone who has actually done that. Good luck let us know what you figure out.

Now for my current issue of an oil fouled plug. Took a look in the spark plug hole, granted it was the old mirror and a flashlight method, but seems to be quite a bit of oil, more than I would think if it's a valve guide seal. Maybe a valve guide itself is loose or cracked. Would you be able to hear a valve guide seal if it was loose? Seen that on a Harley, sounded like a rocker-arm hitting the rocker box cover. Still plan on putting a compression tester on the cylinder, ran out of time today. Can't locate any specs for cylinder compression. Anyone got access to factory service literature? My Chilton's CD only lists the egines compression ratio, and gives you a 75% limit compared to other cylinders. I'd like to know what it came with new, that's where the percentage should come in to play as far as I'm concerned.

Crush
Semper Fi!

 

Sorry, the thread title has P-0304 in the title for the Aug 05 posting.