Needs the 3 spark plug changed every 2 months

Tiny
JWHIT
  • 1999 FORD EXPLORER
  • 6 CYL
  • 4WD
  • AUTOMATIC

I have a 99 ford explorer with a 4.0L OHV engine that needs the #3 spark plug changed every 2 months or The following symptom occurs every 2 months.

The following symptom occurs every couple months then goes way completely after the spark plug is changed. On start up the engine will have a noticeable miss then after about a minute it will clear up and run fine. When driving 40-50mph light acceleration or cruse the engine will start bucking( missing) seems to clear if down shifted or accelerated. I tried ignition parts coil, wires.

The compression is fine. Ford changed ignition parts and intake manifold gaskets 8yrs ago and70K miles. Like stated before a new plug always makes it run good for while. No fouling or abnormalities on plug. Any ideas? Thanks, J

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Sunday, April 29th, 2012 AT 4:33 AM

8 Replies

Tiny
FIXITMR
  • MEMBER

Ok your PCM has 3 diff outputs to the 3 coils the coils share 2 plugs each. Since only 1 plug is acting up that points to the plug wire for the suspect cylinder. Does the plugs color on that cylinder match the other same coil plug?

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Sunday, April 29th, 2012 AT 5:29 AM
Tiny
JWHIT
  • MEMBER

I have already traced the plug wire. Ohmed it out to confirm and even swapped the physical wire from cyl 2 and three. Still made no difference. The plug in cylinder 3 looks the same as cyl. One time I swapped plugs from cyl 2 to 3 and the problem went away for 2 months.
Thanks,
J

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Monday, April 30th, 2012 AT 1:13 PM
Tiny
FIXITMR
  • MEMBER

Have you compared the spark strength/quality on that cylinder?

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Tuesday, May 1st, 2012 AT 7:09 PM
Tiny
JWHIT
  • MEMBER

Yes, and the cylinder relative to other cylinder seems fine. I have heard there where issues with the cyl head cracks etc. I tried removing the plug and re-torquing it. That did not work. No signs of head gasket issues. Any ideas?

Thanks,
J

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Wednesday, May 2nd, 2012 AT 3:26 PM
Tiny
FIXITMR
  • MEMBER

Try a hotter heat range plug? I had plug problems with a tempo and cured it by going to hot plug.

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Friday, May 4th, 2012 AT 9:02 PM
Tiny
PAWEL
  • MEMBER

Same car, same problem. Only difference - cracked ceramic insulator on the spark plug #3.

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Friday, June 1st, 2012 AT 7:27 PM
Tiny
JWHIT
  • MEMBER

I have changed this spark plug at least 9 times since I've owned the vehicle. I torque the spark plug and ensure the gap is correct each time.
Explorer starting to act up again. I think I'll try the hotter plug idea. Will be repairing a valve cover leak soon, so I think I'll change the inject in that cylinder too. Can't hurt

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Saturday, June 2nd, 2012 AT 11:19 PM
Tiny
JIMSCHIRLE
  • MEMBER

I chased this problem for several years. You have a small crack in the head between the intake valve and exhaust valve. This is very common, perhaps inevitable on a 98T head. Coolant leaks into the cylinder when the car sits and it runs rough for 10 to 20 seconds after a cold start. After 2000 to 3000 miles the coolant contaminates the ceramic on the plug and it becomes electrically conductive and causes a misfire. You change the plug and you are good another 2000 to 3000 miles. This occurs on the #3 cylinder (back passenger side) and #4 cylinder (front driver side). K&W block sealer may plug the leak a bit and you can get more than 2000-3000 miles out of a plug. The only real fix is an aftermarket head that has more metal at the point where is cracks. That's what I did for mine. Google "Ford 4.0 ohv cylinder head crack" to see pictures. Good luck.

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Thursday, January 17th, 2013 AT 1:06 AM

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