Engine Misfire/Spark Plug Problem | Ford Explorer Forums - Serious Explorations

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Engine Misfire/Spark Plug Problem


Well-Known Member
May 20, 2010
Reaction score
City, State
Southampton, MA
Year, Model & Trim Level
1996 Ford Explorer Limite
So I have an engine misfire/backfire problem. I've been dealing with the code P0305 for about 2 weeks now. Last week I got the spark plugs and wires changed, and this week I did both coil packs.

Now get this.

Obviously I know its Cylinder #5 with the issue. I ran the car and drove it around tonight with all spark wires plugged in. I could definitely tell it was misfiring, and I got quite a bit of loud engine backfire when accelerating or going up hills. Also there was a noticeable loss of power.

So then, I bring the explorer back home, disconnected the spark plug wire on the coil pack going to cylinder #5, and drove the car the same test route I did before (up the same hills, etc) and the ONLY thing I noticed was the same loss of power! I got NO backfire whatsoever when accelerating or going up hills!

Does this mean the plug or wire on Cylinder #5 is bad? Even though they're both new. Could this be the cause? Like I said, when I drove without that #5 Wire plugged into the coil pack, there was no misfiring/backfiring. Just the same noticeable loss of power just like if I had the wire on.

Any help would be great!! :D This has been driving me insane!! :mad:

You could try plugging the #5 wire into a different plug just to rule it out. I had those codes on my 3.0l ranger and it turned out to be a bad fuel injector.

If it is backfiring you could have a miswired plug wire, worn camshaft, valve problem ect. Having the wire disconnected and the backfire going away tells me that the spark was igniting while a valve was open. verify the plug wire routing and do a compression and cylinder leak down test to check for a mechanical problem.

Fixed the problem!! I got all the spark plugs and wires changed [/B]before[/B] I changed the coil packs. Apparently the coil pack was bad and did something to the spark plug, because when I pulled it out, the tip was all burned! Put a new one in and now she runs sooooo smooth!