Check Engine Light flashing intermittently
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Senior User
Joined: Jul 2007
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From: Honolulu HI.
If it is seeing misfires it will store a code. If it can pick out misfires on a particular cylinder or cylinders it will store codes for those too. It should be P0301 through P0306 on yours. A cheap OBD2 reader will tell what these codes are. If they are all over, then it could be a few things, one of which I haven't seen mentioned here: fuel pressure. How is the fuel pressure on this? At idle and while driving and while having the issue?
I totally get that the newer computer-controlled engines are a bit of a mystery to those of us who learned on old-school cars, but they're not impossible to learn at the conceptual level . . . and once you've crossed into reading stored codes you'll find it can really help with diagnosis.
I totally get that the newer computer-controlled engines are a bit of a mystery to those of us who learned on old-school cars, but they're not impossible to learn at the conceptual level . . . and once you've crossed into reading stored codes you'll find it can really help with diagnosis.
I don't have an OBD reader right now but, I had a P0302 code last time. That was about a year and a half ago... To make a long story short, the CEL would only flash when I went down a really steep hill around here. On flat ground, it would stop flashing. After not going down that hill for a while, the CEL eventually turned itself off; so I just drove it. It's been all good up until recently.
I went to Autozone and had them read the codes for me this time. It said "extreme misfire" on #2 and #3 cylinders. I didn't see the actual codes, but I'm pretty sure it would've been P0302 and P0303. They recommended plugs and wires, but I went ahead and got the coil too. I really thought it was gonna be the coil...
I guess I'll stop by Autozone soon, and have them read the codes again. I'll make sure to get the actual codes this time, instead of just the generic description it showed on the computer.
The light flashes a lot more nowadays.. It probably flashes more often than not.
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From: Honolulu HI.
But I changed all those parts and nothing changed. If anything, the light flashes more often now; but I assume that's because the cats are taking a beating.
The smell of unburnt fuel is getting stronger at idle too.
Yesterday I was on the highway and I turned the OD off, to keep the revs up. I even used first and second gear on my way to the highway, to keep the revs up.... It seemed to take a little longer for the light to start flashing that way, but it did come back after a little while.
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Senior User
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From: Honolulu HI.
She fires right up, and the smell of unburnt fuel (at idle) is strong these days.
When I'm getting on the highway with the pedal to the metal, everything seems about normal...
Lead Driver
Joined: Sep 2006
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I give up.
You try to counter most everything, with I think, I don't believe, I changed this and that etc.
Find out for sure what cylinder is causing the CEL to flash.
Maybe it's a leaking fuel injector or seal ring. Could be a leaking fuel regulator diaphragm.
If you smell gas there is a leak someplace. Remember the flashing CEL is telling you this. If you melt the cats on one side and the rear Ox Sensor, it will cost you big time in dollars and labor.
Best to you. Hope you get the issue solved.
You try to counter most everything, with I think, I don't believe, I changed this and that etc.
Find out for sure what cylinder is causing the CEL to flash.
Maybe it's a leaking fuel injector or seal ring. Could be a leaking fuel regulator diaphragm.
If you smell gas there is a leak someplace. Remember the flashing CEL is telling you this. If you melt the cats on one side and the rear Ox Sensor, it will cost you big time in dollars and labor.
Best to you. Hope you get the issue solved.
Fleet Mechanic
Joined: Aug 2002
Posts: 1,899
Likes: 29
From: Raleigh USA
I think you misunderstood what I said or I wasn't clear enough. If you apply vacuum to the EGR valve at idle and it starts misfiring then you have clogged ports. If you apply vacuum and it stumbles or stalls, then the ports are not clogged and the cause is elsewhere. Sorry if I wasnt clear enough.
FTE Community Team
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Thread Starter
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Senior User
Joined: Jul 2007
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From: Honolulu HI.
ignition on, engine off = 38 psi
@ idle = 32 psi
When I rev it (in park), it goes up to 40... then drops to 29 when I let off... then immediately comes back to 32.
I can't see the guage from inside the truck, so I don't know what it would say while driving.
But thanks for the suggestion. I guess I can cross that one off? (fwiw, I replaced the fuel pump about a year ago)
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Thread Starter
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Senior User
Joined: Jul 2007
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From: Honolulu HI.
I think you misunderstood what I said or I wasn't clear enough. If you apply vacuum to the EGR valve at idle and it starts misfiring then you have clogged ports. If you apply vacuum and it stumbles or stalls, then the ports are not clogged and the cause is elsewhere. Sorry if I wasnt clear enough.
Six years ago, when I did the plugs, wires, and coils, the misfire was really bad. The power was gone and it made a loud clacking sound. I won't even call it a "ping" because it sounded more like two 2X4s being clapped together. It was very bad.. I had codes for three cylinders that time. Hitting the gas only made it worse...
This time, the "misfire" is more like just a miss... It's just vibration and a little bit of stumbling. Hitting the gas smooths things out somewhat.
So, when I applied vacuum to the EGR valve, it only took a little bit to get it to stumble and drop rpms. I'm sure I could've stalled it with a little more vacuum, but I didn't want to break anything. I only gave it about 4 hg.
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Senior User
Joined: Jul 2007
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From: Honolulu HI.
I give up.
You try to counter most everything, with I think, I don't believe, I changed this and that etc.
Find out for sure what cylinder is causing the CEL to flash.
Maybe it's a leaking fuel injector or seal ring. Could be a leaking fuel regulator diaphragm.
If you smell gas there is a leak someplace. Remember the flashing CEL is telling you this. If you melt the cats on one side and the rear Ox Sensor, it will cost you big time in dollars and labor.
Best to you. Hope you get the issue solved.
You try to counter most everything, with I think, I don't believe, I changed this and that etc.
Find out for sure what cylinder is causing the CEL to flash.
Maybe it's a leaking fuel injector or seal ring. Could be a leaking fuel regulator diaphragm.
If you smell gas there is a leak someplace. Remember the flashing CEL is telling you this. If you melt the cats on one side and the rear Ox Sensor, it will cost you big time in dollars and labor.
Best to you. Hope you get the issue solved.
I got the codes read again, and it came up with P0302 and P0303. That was all it showed.
FTE Community Team
Joined: Jan 2019
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Yup, sure can!
Yeah saw that earlier. I've just chased too many rabbits related to [it's a newish pump so it must be good] to let it go at that.
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