davermz450

Hey yall,

I have a 2008 w/ the 4.6 and just drove it across country from KY to NM. When I was about 19 hrs in driving I had a check engine light flash and then go away. Finally, when I arrived in NM the truck started to vibrate like hell and threw a P0300. New COP did the job, no light and about 40 miles since but it still vibrates when I put the AC on. The belt tensioner bounces like crazy but smooths out once the AC is off. When I was having the miss fire the vibration was happening all the time but now its just when the AC is turned on.

Dave

redfishtd

Miles, last plug and boot change ? Basically you are loading the engine with the ac / Not enough misses to set cel . it is possible your tensioner has gone bad but you can test for that .
Do tune up and clean all cop connections .

davermz450

Just put in brand new COP and plugs. I have the tensioner off the truck right now and the bearings are good and no signs of the spring being bad. I am starting to think its the AC compressor....

redfishtd

does it act up? If it does its misfires ,change all rubber boots on plugs . use dielectric grease sparingly . torque plugs in 25 to 28 foot pounds .

norakat

So did you fix your problem? Was it the AC Compressor?

Having same problem on a different model vehicle..

stankyjeans

My guess was the A/C compressor too. Sounds like it's hanging up and on the way out?
I know, old thread, but inquiring minds want to know!

norakat

Read a bunch of other similar problems.. Seems it could be anything on the Serpentine belt system that is applying a load - alternator, etc..