Plug #4 and coil
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Joined: Jan 2005
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From: Florida
Plug #4 and coil
I have to say that this is a great website. Alot of knowledgeable folks here. Here's my problem, I have a 98 Expy 4.6 103,000 miles, that had the #4 plug misfire and the coil pack to that side go bad. I replace all the spark plugs and the coils about 7 months ago. Now I have the same probl;em. This was the heater hose leaking on the plug and causing the misfire. I fixed the leak problem and put in a new plug. It still runs a little rough and no change. My question is... can a misfired plug damage the coil on these engines? And can the misfire cause insufficent flow in the EGR? I will replace the coil but wonder why Ford had the heater hose connection in this spot. It certainly is a tight spot to work in. I love my Ford trucks but sometime they drive me nuts. Thanks for any advice. Ed
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Joined: Dec 2001
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From: Louisville,Ky.
Well, in 2000 or 2001, they changed to a crimped hose instead of a clamped hose to fix this problem.
I would first, pull the wire and look for any moisture in the boot. If so, remove it and apply some dielectric grease to the inside of the boot before putting it back on the plug.
If you still have a problem, swap coil packs from side to side and see if the problem moves with the coil or stays at #4. If it moves, then the coil has failed, if not you may have a bad wire or plug.
Are you getting the P0401 code? If so, the most common problem is a bad DPFE sensor (EGR sensor). If while running, you apply vacuum to the EGR valve and it stumbles or dies, the sensor is probably bad.
I would first, pull the wire and look for any moisture in the boot. If so, remove it and apply some dielectric grease to the inside of the boot before putting it back on the plug.
If you still have a problem, swap coil packs from side to side and see if the problem moves with the coil or stays at #4. If it moves, then the coil has failed, if not you may have a bad wire or plug.
Are you getting the P0401 code? If so, the most common problem is a bad DPFE sensor (EGR sensor). If while running, you apply vacuum to the EGR valve and it stumbles or dies, the sensor is probably bad.
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New User
Joined: Jan 2005
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From: Florida
Thanks for the info. Yes, there was some moisture on the boot. I cleaned it up I did replace the plug and applied the dielectric grease before I had it diagnosed again. I did get a PO401 code and a PO303 and PO304 after I changed the plug. I was told that sometimes it will show that EGR code if there is a misfire. I don't know if thats true. I will try the coil pack switch. The coil pack I installed was from Autozone and not the Ford dealer. Maybe not as reliable as the Ford part.
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