Chcat158000

Hey I’m new here so I’ll try to explain this best I can

I have a 07 4.6 with around 240000KM

it has this rough idle that has me stumped. It will idle like junk in gear, but run smooth in park until the truck gets to temp, then once the engine gets to temp it only idles like **** in park but will idle like butter in drive. (I’m assuming this is because the revs change between park and drive and depending on temp.)

However, if you put it in drive, hold the brake and rev it up to around 600-650 it will start running like **** again.

so it’s a rough idle that only occurs between 600-650ish, right where the idle sits in park at operating temp lol

either way im lost. I’ve thrown coils, plugs, pcv valve, intake manifold, cleaned maf, changed belt, all pulleys and alternator, and cleared KAM. (All motor craft parts) On top of that, the fuel trims are normal and there’s no codes or misfire data. I’ve looked for obvious vacuum leaks and couldn’t find any, however I didn’t look super thorough.

any ideas??? It’s not a horrible shake, and the trucks drives fine but I’m just so annoyed of it. It will shake the passenger seat pretty good and people who hop in notice it instantly.

Any suggestions would be appreciated. Thanks!

edreddy

Hey @Chcat158000 - I picked up a 05 F150 4.6 V6 on Tuesday - and I have exactly the same problem. I mean, exactly.
I've put fuel injector cleaner into the tank - I'm hoping that's the issue. The truck I purchased was from my work, most of it's life it drove only 20-30kph and it has 165'000km on the odo. If the injector cleaner doesn't work by the end of this gas tank, I'm going to change the plugs and clean the MAF sensor next.

What did you want to check first?

Chcat158000

I did spark plug and coils first but it didn’t change a thing. I have no idea where to go with this thing now.

edreddy

I would next try MAF sensor cleaner and then fuel injector cleaner. Something like a can of MAX-Clean from Royal Purple should do the trick. I added some to mine last week, already running way smoother.

Scott Kilmer video here: is a good start.

Chcat158000

Already tried both didn’t change anything

Rac02

Did you ever find the issue. Mine is doing the same thing.

edreddy

I had to change my ERG valve (it threw a code) and new plugs. It's either my fuel injectors or ignition coils. Overall, my truck runs fine even though the idle isn't great. Fuel economy isn't hurt at all, just feels rough at a stoplight or when I first start it after a minute. For a while, I thought it was a vacuum leak but I couldn't find the source.

I may check the coils in the summer and fuel injectors - gonna get a tester first. I got lots of spare parts kicking around to test it on.