Thread: 2000 f150 4.2 misfire

Hello. My truck has a mis while accelerating. I found a leak at the pcv Y and fixed that. I noticed that with the pcv plugged in to the valve cover, it was a constant mis. Now with the valve out of the grommet it only misses half way through 3rd geer it starts, does it slightly after the next shift, then while in <2000 rpms in O.D. it gets bad but once the rpms get up the miss is very small and sometimes stops. Please help me.

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Forgot to mention, i just replaced the injectors. New coil, plugs, wires, cam sensor, cleaned MAF. Still missing while accelerating although it didnt start missing until half way through 4th geer today.

Get a new Pcv valve.

Should pick 1 up 2marrow. Its like $4 at autozone. U really thinl that could b my cause to all this?

Good place to start if what u say is true.

Originally Posted by pjohnston

Hello. My truck has a mis while accelerating. I found a leak at the pcv Y and fixed that. I noticed that with the pcv plugged in to the valve cover, it was a constant mis. Now with the valve out of the grommet it only misses half way through 3rd geer it starts, does it slightly after the next shift, then while in <2000 rpms in O.D. it gets bad but once the rpms get up the miss is very small and sometimes stops. Please help me.

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Forgot to mention, i just replaced the injectors. New coil, plugs, wires, cam sensor, cleaned MAF. Still missing while accelerating although it didnt start missing until half way through 4th geer today.

Try your plug wires and make sure you grease them. If it is 04-up if you can go to a autozone or your local parts store and get just the boots for the coil packs. After time the boots get hard and swell and don't fit tight around the plug causing it to arc against the block without throwing fault codes. This was a problem I had and yours sounds similar the boots only cost about 50.00 max

I replaced the pcv valve and hoses. So after all the new parts i still had a mis. For the heck of it, i pulled out the vacuum line in the intake just before the throttle body and sprayed some carb cleaner. And what u know the mis is gone. Im gonna pull the plenum back off and clean it with some seafoam. I appreciate all the input from everyone.

It's the aluminum plenum. 171 and 174 are still coming up. Is there any vacuum lines that run on the driver side along the firewall or close to it?

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And where are the IMRC rods?

I replaced the 90° elbow awhile back. Where are the IMRC rods and vacuum lines.

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U also mentioned a vacuum line in the pax fender. I've never heard of the pax fender. Maybe you can help me and tell me where exactly that is.