CKsBAT

My 5.4 is starting to idle a little rough. Not missing, but not real smooth. It is worse in gear, not sure if that just magnifies it. All the basics have been done, MAS, throttle body fuel and air filters, plugs etc. could a bad Cop do this or if the go bad they just don't work at all?
Thanks

Tommy J

I think a cop could just have a low grade misfire and not be totally shot. Could also be an injector issue. I think thats what Im dealing with. Then theres the vct selenoids, fuel module under spare tire and on and on. Theres a ton of stuff that can cause a rough idle. I even did my fuel pump. Do you have a scanner you can use

Especial86

iTrader: (1)

See if it idles smoother with the AC and headlights on first.

Pull the passenger side VCT solenoid and have a look at the screens.. Update them to the latest revision if they are old.. New solenoid to cover seals are good to have handy for this.. If you have an 07+ the valve covers need to come off for solenoid service.

Could be a cop or a plug too, but I'd read what the computer is saying before throwing parts at it either way.

CKsBAT

No codes are showing at this point, I'll look at the soleniods. The truck is an 05.

CKsBAT

VCTs look like they just came out of the box, so not clogged.

VTX1800N1

Check the EVAP purge hose between the solenoid on the driver side firewall high and the intake manifold on the passenger side near the throttle body. It tends to rot and induce a vacuum leak. The 04-05 3V tends to run lean already.

CKsBAT

That was the problem, thanks man. This forum is always awesome, probably saved me a couple of grand over the years. That $&@#% hose just crumbled when I took it off. Seems to be the same quality as the stupid window regulators 😡 that I'm replacing next week.

VTX1800N1

Awesome! Happy you found the problem. Chasing intermittent problems like that can be very frustrating.

rlorion

I have the rough idle thing going on and when I am going up a slight hill and in overdrive under load it will knock and then start to shake like a ****. Could this be a VCT issue? I had the fuel system flush with new plugs and fuel filter done @ the dealer. I hope I don't need to spend thousands on a Cam Phaser change.

VTX1800N1

Usually that is a problem with bad ignition coils or worn sparkplugs.