A few months back my 1999 F-150 5.4 V8 (205k) was running very rough when I would press the accelerator slightly, but would run ok when I punched it. It was also throwing the "lean banks" error codes. I changed the plugs, COP's, and injectors and that fixed the rough running problem as well as the error codes. It seemed to be running pretty good for a truck with 200k on it. A few days back it rained pretty good. Of course I had to frive through some puddles, but nothing very deep at all. All of a sudden the truck is running rough again and this morning it threw the error code again. I figured the plugs may have gotten wet and just needed time to dry. It has now been about 3 days and the truck is still running rough.

Could this be because of the engine getting wet? It seems like the truck should be able to go through some rain without causing problems. Do I need to reset the computer now that the plugs should be dry? I did apply dielectric grease to the COP's/plugs when I changed them. This pisses me off because the truck was actually running good and now i'm back to the same problem. Any ideas?

Thanks.

 

Have you checked for codes? Sounds like you may have lost some coils in to the water. If it's running poor like that, there's got to be a code stored for something in the ECM.

 

Sounds like an ignition issue. Check plug boots could be holding moisture and could take a long time to dry out. May be time to replace them.

 

This really sucks! It's already been a week and it's still running like crap. Could the inside of the COP's still possibly be wet? They were all replaced new a couple months back, so I know they were good.

Will getting them wet ruin them, or will they still be good once I dry them off, if that is indeed the problem? I was thinking of taking each one off and just taking a look. I don't know what else to do at this point. I hope it doesn't keep doing this every time it rains.

 

Definitely.
Hows your luck ? If you really lucky, that might work.
You can post the DTC, - that would help you most right now. That way I can help quite a bit more anyway.

How did you go about greasing?