97 Mountaineer 5.0 V8 Misfire

TUSCANITIB

MEMBER
1997 MERCURY

Definitely need some advice here. I was a general tech now working at a Toyota dealership. I have a 97 mountaineer 5.0 v8 that I had an intermittent p0304(cylinder 4 miss) at heavy acceleration. I did a complete tune up(plugs wires fuel filter and fuel system cleaning). Now about 3 weeks later its now a dead miss cylinder 4. I checked for spark from the plug, nothing. I used an inline spark tester that lit up like a christmas tree but still not spark from the plug. Common sense says replace the new bad plug and recheck. It ran decent for about 15-20 minutes than went to crap again. My next step is checkin injectors but Im just wondering if anyone has found a solution to this problem. I have scanned the internet and asked everyone and no one has a definite answer, but everyone seems to have the same problem. Any help would be greatly appreciated. Thanks

Thursday, November 15th, 2007 AT 8:34 PM

3 Replies

BLACKOP555

MECHANIC
10,386 POSTS

Yes I believe that if you have a distributor you may need to check the rotor and cap for cracks and wear and carbon build up, I would replace iwth a new rotor and cap. For that cylinder I would put in a new spark plug and wire going to it, let me know if this works.

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Friday, November 16th, 2007 AT 8:11 AM

TUSCANITIB

MEMBER
2 POSTS

I apologize if I was misleading. Its 2 coil pack setup like normal in those years. It has all brand new plugs and wires and still the same problem. I asked a couple friends of mine with general shops and all said its 1 of 3 things. Either the injector is stayin open and floodin the cylinder out, exhaust valve is burnt, or there is an intake leak in just that one intake runner. Next step is a compression test, fuel pressure test, and if all else fails a leak down test. Ill keep this updated as to my conclusions.

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Friday, November 16th, 2007 AT 3:40 PM

BLACKOP555