08 4.2 misfire
#1
02-23-2019, 07:26 PM
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08 4.2 misfire
i have an 08 with the 4.2 and it is running rough at idle and has backfires while driving. Replaced the coil pack yesterday and didn’t help except for the check engine light going off. Had it scan before the coil pack swap and it showed a misfire on every cylinder. Any ideas on what else besides plugs? Has 110,000 miles on it.
#3
02-23-2019, 10:47 PM
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These have about 60k on them and I have them to replace but the last time it acted like this the coil pack was bad. This one didn’t look bad after I pulled it off. I’m showing codes 300 through 305. Plugs are very hard to get too. Ford place replaced them the first time as a courtesy for something else.
#6
02-24-2019, 03:27 AM
Which brand are you using for your tune-up parts? If you are using inexpensive coil pack, wires, and plugs......those could all be a problem. Did you use dielectric grease?
Ford MotorCraft OEM spark plug wire set is 7mm, which was good enough to leave the factory with. There are wires with thicker gauge. I don't know if they are any better. May not do anything special, except for work without failure. But anytime you try to save a few dollars with something less expensive, it never works out well. Some manufacturers offer a spark plug wire set specific to the F-150 4.2, which is what you want as opposed to generic wires. Look for 8mm wires, numbered for each cylinder so that you don't have to figure it out, and think about the reputation of the seller. Are you buying Taylor wires, or "made in China, sold on eBay"?
The coil pack should be Motorcraft. Not that Motorcraft doesn't have issues. Motorcraft ignition coil packs are known to eventually fail with misfires, otherwise we would never have to replace them. A lot of people like Denso, since Denso is the OEM. I'm using a MSD, which is working without issue so far, only because of pricing and availability. There are over a dozen inexpensive ignition coil packs selling for $10 - $20, and none of them work well. Depending on where & when you buy it, the Denso & Ford Motorcraft could be $75 - $100, but at least they work.
Everyone says that you should only use Motorcraft spark plugs. There are other brands. And almost surely, the less you spend, the worse it gets. Some have had good results with Denso & NGK. I'm currently using E3, without issue. On some of the V8 & V10 engines where the spark plugs were breaking, Champion offered an alternative spark plug.
If starting off fresh with new tune-up parts does not solve your problem, then there is something else going on.
Ford MotorCraft OEM spark plug wire set is 7mm, which was good enough to leave the factory with. There are wires with thicker gauge. I don't know if they are any better. May not do anything special, except for work without failure. But anytime you try to save a few dollars with something less expensive, it never works out well. Some manufacturers offer a spark plug wire set specific to the F-150 4.2, which is what you want as opposed to generic wires. Look for 8mm wires, numbered for each cylinder so that you don't have to figure it out, and think about the reputation of the seller. Are you buying Taylor wires, or "made in China, sold on eBay"?
The coil pack should be Motorcraft. Not that Motorcraft doesn't have issues. Motorcraft ignition coil packs are known to eventually fail with misfires, otherwise we would never have to replace them. A lot of people like Denso, since Denso is the OEM. I'm using a MSD, which is working without issue so far, only because of pricing and availability. There are over a dozen inexpensive ignition coil packs selling for $10 - $20, and none of them work well. Depending on where & when you buy it, the Denso & Ford Motorcraft could be $75 - $100, but at least they work.
Everyone says that you should only use Motorcraft spark plugs. There are other brands. And almost surely, the less you spend, the worse it gets. Some have had good results with Denso & NGK. I'm currently using E3, without issue. On some of the V8 & V10 engines where the spark plugs were breaking, Champion offered an alternative spark plug.
If starting off fresh with new tune-up parts does not solve your problem, then there is something else going on.
Last edited by Fifty150; 02-24-2019 at 03:29 AM.
#7
02-24-2019, 03:31 AM
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#8
02-24-2019, 03:42 AM
Suck
Bang
and
Blow
You need air, fuel,and spark. Any issues with fuel delivery? Fuel pump, fuel filter, fuel injectors? Check your air delivery. Any obstructions? Is your filter clean? How about the intake from the filter housing to the throttle body? Are any of the sensors damaged or failing? Is the throttle body dirty? Also, check for compression.
Or you using cheap gas?
Bang
and
Blow
You need air, fuel,and spark. Any issues with fuel delivery? Fuel pump, fuel filter, fuel injectors? Check your air delivery. Any obstructions? Is your filter clean? How about the intake from the filter housing to the throttle body? Are any of the sensors damaged or failing? Is the throttle body dirty? Also, check for compression.
Or you using cheap gas?
#9
02-24-2019, 04:16 AM
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#13
03-07-2019, 11:48 AM
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#14
03-07-2019, 01:58 PM
