Very Rough Idle when Cold
I've done some searching and have seen mixed results, so I thought I'd start my own thread.
This is for my í07 FX4 5.4L. Only modifications are Gryphon tuner, exhaust, and CAI. Iíve already ruled out the programmer as a possible cause by returning it to stock for an entire tank of gas.
Had my 60K tune-up done a few weeks ago. This included the regular stuff along with an early plug change. It went very well and none broke, thankfully.
Well, about two weeks after the tune-up I noticed the truck idling rough during cold start-up. To go along with that, it had some hesitation when pulling from a dead stop. For example, if I started the truck and pulled out to my neighborhood stop sign, the engine hesitates when pulling away from the stop sign. The RPMs bounce around like crazy.
They also bounce around during cold idle, and I can feel the engine vibrating (jerking is the best way to describe it). I can rev it to between 1200 and 1400 RPMs and it gets really badÖ..the truck starts shuddering. Feels like it might die but doesnít.
This all happens when the engine is cold. Once it starts to warm up itís fine---no hesitation and no bouncing RPMs.
Well, it hasnít been that bad so Iíve been trying to wait until a good time to take it to the mechanic in order to avoid having to get a rental car. We have two days off work next Thursday and Friday, so Iím trying to make it to then. Iíve just been letting the truck warm up for 10-15 minutes in the morning before pulling out.
Flash forward a few weeks to this morning. The past few days I havenít been warming the truck up like usual. The hesitation seemed to be gone but the RPMs still bounce around at idle. Iíll pull up to a red light and they bounce between 600 and 900 RPMs constantlyÖ.slightly shaking the truck. Nothing major but it isnít very comforting having the feeling that something is wrong.
This morning it was really bad---the worst itís been so far. The rough idle was really rough, the hesitation was back, and worst of all it did it for about 10 minutes even after the truck warmed up. Driving down the road the truck was shaking terribly due to the engine running so rough. It was vibrating so bad I was scared that I wouldnít be able to make it to work. Once I got on the interstate it was fineÖ.
Mechanic is out due to medical emergency for a few days, so Iím going to try to get it in next week. From my research and talking to my mechanic (about two weeks ago), we seem to think itís one or more of the coils going bad.
Any other ideas? From my research around the boards it could be a few things (vacuum leak, coils, etc). What do you guys think? This has me worried because of how bad it was this morning.
Thanks for any help!