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Cylinder doesn't fire regularly - what is repair? and how much to fix?
1999 Ford Explorer

Cylinder doesn't fire regularly - what is repair? and how much to fix?

(1999 Ford Explorer)
Engine runs but is moderately rough; seems misfiring. Mechanic sequentially pulled each spark plug sire from the distributor cap with me there. For one cylinder there was no 'rev' as he raised the wire a ltle up then down to the cap. He said that something seemed wrong with one cylinder. But he also noted (accurately) that the spark plug wires looked fairly new. I changed spark plugs and wirtes about 18-24 months ago. What might be the cause and repair for a cylinder if the distribuor cap and spark plug wires are sound?
1 answer & 1 comment
Popular Answer
on December 28, 2010
First and foremost, run a compression test on that cylinder, that is step #1, it needs to have at least 150 psi compression.
Then, just because the plugs and wires 'look good' is no guarantee. I have seen brand new cars in dealerships have a bad spark plug with 10 miles on it, it can happen. Also, these 4.0 Ford V6 engines get vacuum leaks in the manifolds if it is a plastic manifold, so is there a check engine light on and if so what is the fuel trim, that will tell if the misfire is vacuum leak related or if it is a wire, coil pack, plug ( your engine has no distributor, it has a coil pack ) as long as the compression is 150+. If you have any P0200 type of P0201, P0202 etc codes then that is a bad injector, which can also cause a misfire.
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on December 30, 2010
Thanks much! This will help me have a more informed talk with the mechanic later today.
General Diagnosis
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on December 28, 2010
First and foremost, run a compression test on that cylinder, that is step #1, it needs to have at least 150 psi compression.
Then, just because the plugs and wires 'look good' is no guarantee. I have seen brand new cars in dealerships have a bad spark plug with 10 miles on it, it can happen. Also, these 4.0 Ford V6 engines get vacuum leaks in the manifolds if it is a plastic manifold, so is there a check engine light on and if so what is the fuel trim, that will tell if the misfire is vacuum leak related or if it is a wire, coil pack, plug ( your engine has no distributor, it has a coil pack ) as long as the compression is 150+. If you have any P0200 type of P0201, P0202 etc codes then that is a bad injector, which can also cause a misfire.
Sign in to reply
on December 30, 2010
Thanks much! This will help me have a more informed talk with the mechanic later today.

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