My 07 f150 4.6 has a rough idle and stalls when I come to a stop. It starts right up and will do it again. It also has an occasional slow start. Usually when its warm outside. But I have replaced the MAF sensor, spark plugs, coil packs, throttle body, 02 sensors, and fuel filter. I fixed the codes that it was reading with all those replacements but it still has a rough idle and stalls. Now I'm at a loss. I'm thinking it's either clogged cats, vacuum leak, or a evap canister purge valve. Its showing bank 1 o2 sensor running lean. Any suggestions? I don't want to start replacing unneccassary parts if I don't have to.

 

I have a 2001 f150 and it is doing the same thing. My son drove it the other night and then looked underneath to find the catalytic converter glowing red as fire. He told me that was the cause of the rough running and dying at idle. So I suggest smelling the exhaust for rotten eggs smell and after running a bit at night, look at catalytic converter.

 

Have you replaced your FPDM yet? If not, have you pulled it down and inspected it?

 

Also, what spark plugs and what coils did you use ?

 

No I have not replaced the FPDM. Never thought about it actually. I put Bosch double iridium spark plugs in and moto vecor coils in. It was showing a misfire on cylinder 6 until I replaced both.

 

At a minimum I’d inspect your fpdm, but if it’s original, I’d just replace it anyway as you are probably on borrowed time.

They are known to cause a myriad of symptoms as they start to go bad. Eventually they can/will leave you stranded (I’d keep a new one under seat if I was running a 13-14 year old original).

Non motorcraft plugs and coils generally receive a thumbs down. If you saved orig coils, you might consider new boots/springs and putting them back in.

 

As a fellow 4.6 owner, please update thread as you go, always helpful to learn the outcome / fixes.

 

Ok. Sounds good. I'm going to do some work on it through out the week and I will let you know what I come up with.