Gentlemen,

2001 f150 extended cab flareside 4x4 4.6L v8, M5od manual, 196,539 miles this morning. the clutch slave is going out so I have some grinding and extra noise but recently the motor began to run like crap. I took it and coded it. "p0403, cylinder 4 misfire" is what it read on the obd scanner screen... I had a similar issue with the COPs not working and actually allowing water into the spark plug cylinder. I replaced them all at 100,000 miles or so with new motorcraft plugs at that time. Fixed the problem and nothing since that time. Not sure why I did them all but I did. i was dumber 96000 miles ago. I also took down the intake and cleaned all the ports and crap out of it also. Yesterday took out #4 (PITA on passenger firewall) and it looks fine. No evidence of leak, spark plug a light tan, firing well without problems, and even gapped properly still. My question is first I understood the p0403 to be EGR related, not cylinder #4 misfiring...seems odd.

2nd: I'd like to avoid just throwing parts at this problem. The EGR is simple enough to replace and if that's what is needed so be it. I'd rather do it right the first time.

I've checked all of the vacuum lines, fittings, attachments. No leaks detected with smoke/brake fluid tests either. Good suction at the PCV, all good.

Thanks gentlemen.

-Dave

 

First thing is you have to report the code accurately.
403 is not a misfire code.
It is an EGR test fail code report for circuit failure.
Misfire codes are 30x coded
Take a new look and see what you have.
Then you know what your chasing.
Good luck.

 

I knew it.
Idiot at AZ argued with me and I didn't have enough confidence to hold him to what he was saying.
Frick. Thanks Bluegrass 7. I'll take it elsewhere and figure out what's going on. EGR has caused me problems before.
Thanks again. I'll report back once I get my crap together.

DN

 

Darned if I took the truck to 3 other places (autozone, oreilly's, and advance).
All 3 read P0403 (misfire #4 cylinder). In retrospect the plugs probably need to be changed anyway. If nothing else i'll move the #4 COP to the #1 position so it's easier to get out should it act up again. Can't see a need to change the COPs if they're measuring ok on the multimeter. Obviously I'll put some more dielectric grease on them and see what I can get. Figured on cleaning out the throttle body again. Did it about 90,000 miles ago, figures she's probably due for that again.

 

I can't tell you what you really have.
Best you look up the codes for yourself.
403 is an EGR CODE.
304 is a misfire cylinder 4.
Note the reversal of the numbers on the ends.
.
You need to see the code for yourself to be sure.
.
If you feel the misfire in the engine than it is a misfire.
If you do not, it is likely the 403 code because the 403 won't cause a misfire because it is a 'test' failure of the EGR system.
.
Take charge and find the situation for yourself.
Until you do you don't know what your chasing for repairs.
Good luck.

 

Thanks for the info Bluegrass7. I'll keep at it and see what I can come up with.




DN

 

Some makers of Readers and Scanners insert their own description text that tends to be misleading unless the user manual is consulted for interpretation.
I would only guess that the display as you see it has an explanation for the way it displays.
On some makes, the auto mfgers uses different codes for the same functions used in others and coded per the different engines in the same mfger line.
Some codes are industry standard, some are mfger choice.
.
I would get a different Scanner and read your codes again.
On code look up, use only the FORD list and not a general list.
A good source of Ford codes is Superchips website for Ford.
It will be about 20 pages for print out as there are more than 2000 codes but one still needs to know more that just the few words in the descriptions to really know what it's all about.
A 304 misfire is just that and needs no more but a code like 402 needs more because it is a system test failure that needs more background to understand.
You can see that a store clerk may only depend on the code description shown and be misled on any given vehicle.
Good luck.

 

Yeah for sure. Thanks much