04 Ford Ranger Idle Misfire

Tiny
MANGERIS1
  • MEMBER
  • 2004 FORD RANGER
  • 6 CYL
  • 2WD
  • MANUAL
  • 80,000 MILES
I have a 2004 Ford Ranger 3.0 V6 with about 80k miles on it. A few years ago, while I was idling, the check engine light started flashing and it started running rough. The RPMs lowered to about 800 and the needle was bouncing a bit. Ten seconds later it picked right back up.

This would happen sporadically but it became more and more constant until it would do this anytime I stopped the truck and idled. However, whenever I started driving the power would kick right back in. The problem only happened when I idled.

The check engine light eventually stayed on. I used a code reader and it had two--that the truck was misfiring under 1000 RPMs and that the #6 cylinder was misfiring.

I took it to a shop and they diagnosed it as a bad plug (their code said it was the #4 cylinder). I paid them to replace the plug, drove off the lot and at the first stop the truck started running rough again.

The shop wants to tear down the engine and I'm not able to have it registered until it passes smog--which it won't because the check engine light is on. Any ideas? I've changed plugs and wires and I've cleaned the air sensors.
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Wednesday, May 11th, 2011 AT 5:31 AM

11 Replies

Tiny
MERLIN2021
  • EXPERT
Code for #4 is p0304 for six its p0306 compression test will tell if engine work is needed or if you have a bad injector or coil. Try moving the coil to a different cylender if problem movrs with it replace coil.
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Wednesday, May 11th, 2011 AT 8:39 AM
Tiny
MANGERIS1
  • MEMBER
The compression test came up normal. I'll try moving the coil. Thanks!
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Wednesday, May 11th, 2011 AT 4:23 PM
Tiny
MERLIN2021
  • EXPERT
Fixed?
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Saturday, June 25th, 2011 AT 4:05 PM
Tiny
MANGERIS1
  • MEMBER
Not sure. The coil pack for the 04 Ranger isn't the kind that you can move the coils around (I was told you could with older versions). I couldn't get a shop around here to bench test it so I swapped it out with one that I know works properly. Because the truck's not currently registered I've only let it idle and the CEL hasn't triggered yet. I'm hoping to put some miles on it soon to see if that was the issue. I'll add an update once I'm confident either way.
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Saturday, June 25th, 2011 AT 6:22 PM
Tiny
MERLIN2021
  • EXPERT
Ok I'll check on you.
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Saturday, June 25th, 2011 AT 6:32 PM
Tiny
MANGERIS1
  • MEMBER
No luck. Drove it around today and it once the truck warmed up, it started misfiring each time I idled for at a stop light. The CEL flashes and the truck misfires for about 20 seconds or until I start driving before the power kicks back in and the CEL goes away.
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Tuesday, June 28th, 2011 AT 3:39 AM
Tiny
MANGERIS1
  • MEMBER
I took it in to a local shop today. They did another compression test and this one came up bad. I'm going to give in and let them take care of it. They want to do a valve job.

The only thing I'm concerned about is that the issue is intermittent. The way it comes and goes when idling (and the fact that another reputable garage misdiagnosed it) makes me worried that the problem isn't what it appears to be.
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Tuesday, June 28th, 2011 AT 7:27 PM
Tiny
MERLIN2021
  • EXPERT
Test should be done on warm engine, all plugs removed, engine cranked three times with fuel relay removed. Test dry then test with a few drops of oil in cylender.
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Wednesday, June 29th, 2011 AT 1:19 PM
Tiny
MANGERIS1
  • MEMBER
I think that's probably why the first garage missed it. Once it's back from the shop I'll post an update.
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Wednesday, June 29th, 2011 AT 3:26 PM
Tiny
MANGERIS1
  • MEMBER
Spoke with the shop today. Exhaust valve in the 5th cylinder was sticking. I sent them the TSB on the Ford heads that were manufactured wrong to make sure they replace them if that's what caused the exhaust valve to go bad.

Makes sense that at idle the valve would stick and then free up once the truck once the truck was in motion.

I get it back on Tuesday. I'll follow up on whether it's fixed or not.
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Friday, July 1st, 2011 AT 4:54 AM
Tiny
MERLIN2021
  • EXPERT
Ok
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Friday, July 1st, 2011 AT 8:38 AM

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