Inconsistent miss fire | Ford Explorer Forums - Serious Explorations

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Inconsistent miss fire


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August 27, 2014
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1994 Ford Explorer
hey guys, just replaced the headgaskets along with upper end gaskets, fired it up and ran good until it warmed up, then started getting a random miss at idle, it would sort of stumble, then it would go away, if I revved it while missing it would stumble then clear out and run good. Seems to be running rich, smells rich from exhaust. Any ideas?

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also have a random idle fluctuation, not all the time. It will idle good, then fluctuate for a second, then go back to normal. Got me stumped. Also running pretty rich

Being that you were in that deep, I'd check compression and maybe even buy a leakdown tester. Did you have the heads checked at a machine shop?

Yep had the heads resurfaced, and a valve job done

Went ahead and compression tested, all showed good at 150psi at the highest and 140psi at the lowest cyl. Manual shows anything over 101 for this engine. So I'm good there. All plugs are new including wires, all gapped at .54

Make sure you plugged the fuel pressure regulator vacuum line back in.

Yeah I plugged it in on reassembly, but it's worth rechecking so I'll look after work tomorrow

1st to check is stuff you touched. vacuum lines, injector seals, vacuum tree, intake gasket. A stumble can be an ignition coil issue. check ground to it. Check all the connectors you may have not plugged in.

Went over everything, looks good, pulled check engine light code 341, 10, and 111. From what I understand 341 is octane adjust service pin open, and 111 is system pass. And I don't know what 10 is.

Did test one more time pulled code 335 for eve voltage higher than expected

Check the connection to the Camshaft Synchronizer at the back of the engine, it is used to time the injectors like the Crankshaft Sensor is used to time the ignition.

Code 335 has to do with the DPFE sensor. If you wind up replacing it I reccomend the Wells/Airtech Re-engineered one. I got mine from Autozone and it's metal not plastic. Consider replacing the EGR valve at the same time, I had EGR related faults when I got my 94 and once I got them resolved it runs great.

Good Luck

Yeah I pulled a KOER code 327 also. All codes I'm pulling are egr related. Which could easily cause all my problems. I never touched the cam synchronizer when doing the headgaskets

Where does the vacuum line from the egr itself go to? Maybe I have vacuum lines switched up. Anybody have a diagram of what vacuum lines go where?

Miss fire is gone, but I drove it and it's down on power, and running rich still. Anybody have any diagrams on vacuum lines? Maybe I have them switched? The way it is right now is I have one going from the EVR to the vac tree, one going off the EVR to the egr, and two from the dpfe going to the egr tubes. Also pulled a code 538.

It's got me stumped. I can't figure it out. Any help would be greatly appreciated

Also pulled code for 02 sensor lean

A very simple way to find out if this is EGR related is to pull the line off the EGR valve. Be sure to plug the vacuum line with a screw. If it runs good after that, you have a problem with the EGR system. If not, it could still be the valve itself, ford recommends they be replaced every 50k miles, as they get soot and other crap inside.

Code 538 means you did not perform the KOER test correctly.

You have multiple EGR related codes, one which is almost always a dead DPFE. I think the best thing to do is replace both your DPFE and EGR valve and go from there.

Well i went ahead and replaced the DPFE sensor, fixed all my problems! No more check engine light, idles good, not running rich anymore and has plenty of power! Thanks everyone for the input