My 1998 f150 4.6l v8 Triton coded p0302. I thought it might be the fuel injector, so I swapped #1 with #2. Took it to Autozone and got a p0304 code! Please, any ideas what it might be?
I replaced fuel filter, oil and filter, plugs, plug wires, pcv valve.
Tested fuel pressure, the 2 coil packs, #2 injector & wire harness, egr valve.

Seems to idle very nice. Runs strong for about a mile, then starts shaking at acceleration, the cel starts blinking then settles to a solid on.

The ex-mechanic at Autozone told me I had a bad dpfe for sure but that would not cause this problem. I did read a post where someone said the egr system could cause this type of misfire on different cylinders due to poor air/fuel mixture????
Oh, also, my egr solenoid has an odd exhale noise a few seconds after I turn off the engine. It lasts at least 5 seconds. Sounds like pressure being released.

Any suggestions would be greatly appreciated. Thank You,
Jeff

 

Did you get a p0401 or p0406 DPFE code? Those code would indicate a bad dpfe.. p0302 is either a bad plug a wire a coil an injector or you have lost compression in that cylinder. That code alone has NOTHING to do with the DPFE, Use Motorcraft parts Plugs, wires, coils. Get your Motorcraft parts at rock auto.com for a nice discount. Start with the plugs. Do them all..

 

I would say plug or wire. But he sais he replaced them. After plugs and wires have been changed, injectors checked and maybe swapped and coil packs replaced.. still a misfire?
Time for compression check I guess.
What plugs, wires, coil packs, pcv valve did you put in?
I would try one more time to swap a few things around and make sure you RESET the pcm every time you swap 2 around.

 

Yes, I forgot to mention, I did get a p0401. I was gonna check compression, but then the #2 I'd been working on no longer had a code. I only got the p0304. So I figured the issue had nothing to do with a particular cylinder. Each time I work on this, I disconnect the neg battery cable. I read that resets the pcm. True?

 

If you replace the DPFE get a motor craft one. Rock auto has those to. Half the price the steeler wants for them..

 

After reading some other posts, I decided to try unplugging the egr valve and blocking both ends. (hose and tube where it connects to egr), took it for a ride and got the same thing. Idled great and ran great for about a mile, then started missing horribly upon acceleration. At that point, it may be missing the whole time, but it runs along so smooth until you accelerate that you cannot tell. So, does that rule out any egr issue, or did I do the test wrong?

 

its probably a bad coil. try replacing the one for the right side.. again use motorcraft parts.

 

Hey, the Auto zone dude got one right!

Sounds to me like you installed Autolite plugs.

 

He's not answering, - not a good sign lol.

 

Rock has them now ? Cool, I didn't know that jethat


jaybeez, -

Double check your firing order, - you never know .. -

 

yeah you have to look under egr pressure feedback sensor
MOTORCRAFT Part # DPFE4 More Info {Clip Mount #4U7Z9J460AA}
4U7E-9J460-AA

Part Image
$32.79

 

Sorry guys, I've been busy on the truck. Yes, Autolite plugs....... Seems like some mechanics highly recommend them along with OEM parts and others call them crap. Use Ford - no use Bosch, no Autolite, not Motorcrap, never buy Bosch..... I don't know who's right at this point. That's about all I've ever used on my cars, but you may be totally right.
However,
I may have just discovered my problem! We'll see. I went to pull my currently misfiring plug #4 out and discovered there was oil surrounding my plug deep down in that hole. That reminded me that one of the first things I suspected was the oil I found around my #2 cylinder. I forgot, because I steam cleaned the area and it never came back. I don't know, perhaps that small leak plugged itself and the oil forced itself out in another place - I understand old gaskets can do that. So, I cleaned it all up and added quite of bit of dielectric grease in and around the boot. I just drove a few miles and it feels like a brand new truck. When I got back and looked at #4, there was no oil around it. Maybe it's a very slow leak. So, I am assuming this would be the valve cover gasket?? Any opinions would be appreciated.

Thanks for all the advice so far folks!!
Jeff

 

Your truck is what 12years old? its been running fine most of that 12 years with what? MOTORCRAFT parts. Modulars especially non PI heads HATE autolite plugs. Buy motorcraft parts for original equipment performance. There is a sticker on your trucks engine compartment that warns you to use motorcraft parts.. 90% of the guys on this board will tell you the same thing. The safe bet is motorcraft.

 

Okay, good enough. My last ones were those Bosch double point plugs. They lasted a long time. I'll keep an eye on the Autolites performance and change when I have to. So, would oil in the plug hole be from the valve cover gasket for sure?

 

The odds of oil leaking into a sparkplug hole from the valve cover are almost non existent.In the first place the gasket is nearly indestructable and the way the top of the head is tilted leads oil to leak down thethe head away from the center. More likely if it really is oil its comming from the PVC line. Are you SURE its not antifreeze? there are water lines for the heater core that run above that side that do fail. Oil is pretty hard to get in those holes.. not impossible but almost.