Another misfire problem
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Another misfire problem
I have a 99 F-250 V-10 Auto 99,000
Started to run rough, first noticed from a big vibration at idle while sitting at a stop light, then a random miss during driving from that point on,
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I have had an intermittent P401 code – insufficient exhaust gas detected.
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And now P300 and P304,
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I figured I would start with by checking out the #4 spark plug and coil pack, but am I looking at a bigger problem with the 300 code?
Started to run rough, first noticed from a big vibration at idle while sitting at a stop light, then a random miss during driving from that point on,
<o
></o>I have had an intermittent P401 code – insufficient exhaust gas detected.
<o
></o>And now P300 and P304,
<o
></o>I figured I would start with by checking out the #4 spark plug and coil pack, but am I looking at a bigger problem with the 300 code?
Post Fiend
Joined: Jun 2003
Posts: 5,643
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From: NE Texas
First of all, yes, a bad EGR will cause a rough idle.
Secondly - the P0300 means that you have an intermittent misfire but it's just random. This can be just the #4 cylinder (plug or coil) or, as I have learned, can be a spike in any COP.
Check the plug in cylinder #4 and get ready to replace the COP, or at least a boot, then see what happens.
I would check the codes afterward, but it looks like the EGR is trying to fail also.
Secondly - the P0300 means that you have an intermittent misfire but it's just random. This can be just the #4 cylinder (plug or coil) or, as I have learned, can be a spike in any COP.
Check the plug in cylinder #4 and get ready to replace the COP, or at least a boot, then see what happens.
I would check the codes afterward, but it looks like the EGR is trying to fail also.
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
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From: Long Island USA
Sounds more like a vacuum leak, an EGR stuck open would mean too MUCH exhaust detected, not too little. And the EGR wouldn't cause idling issues unless it was stuck open.
Too little exhaust detected, random misfire? Vacuum leak.
I might be barking up the wrong tree (again), but something doesn't make sense.
Do what Big Orn says, check out the #4 plug and boot, might have some moisture in the hole.
But also check that PCV plumbing elbow.
The "insufficient exhaust flow" is usually the DPFE going bad, but definitely check for vacuum leaks first.
Too little exhaust detected, random misfire? Vacuum leak.
I might be barking up the wrong tree (again), but something doesn't make sense.
Do what Big Orn says, check out the #4 plug and boot, might have some moisture in the hole.
But also check that PCV plumbing elbow.
The "insufficient exhaust flow" is usually the DPFE going bad, but definitely check for vacuum leaks first.
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Pulled the #4 coil and plug last night. The boot was busted in half, and coil element was brown, could not tell if it was dirt or corrosion, so I cleaned it up a bit then swapped the #1 coil to the 4 position to see if the 304 code would change to a 301.(moving the suspected bad coil to a new position) And wrapped a generous amount of electrical tape around the broken boot.
Then cleared the code memory
Drove to work this moring and the truck drove fine, No codes registered,
I will give it a little while longer to see if the EGR code comes back., and if the misfire problem is solved by fixing the rubber boot then I get a replacement boot.
Then cleared the code memory
Drove to work this moring and the truck drove fine, No codes registered,
I will give it a little while longer to see if the EGR code comes back., and if the misfire problem is solved by fixing the rubber boot then I get a replacement boot.
