Ford F150 - Strange Idle (2004, 4.6 V8)

aksival · Posted: Wed Sep 03, 2008 4:25 am Post subject: Strange Idle (2004, 4.6 V8)

The other day I realized a strange idle pattern when I was sitting at a light. The tachometer generally shows under a thousand and the truck gets a bit shaky, then it revs and shoots up to a little over a thousand. This happens every 15-20 seconds or so.

It's just enough of a force to move the truck a little if I don't have my foot on the brake firmly.

I'm guessing (and hoping) that this is probably just an old sensor that needs to be replaced, but I figured I'd ask the experts. The truck is about to hit 36k this week.

Anyone seen/heard of anything like this?

Edited: I just had to get the battery replaced over the weekend (the old one was original and completely dead). This may or may not have something to do with it, but the problem did seem to occur shortly afterward. The truck has run perfectly until this.

123ford · Posted: Wed Sep 03, 2008 12:21 pm Post subject:

Could be dirt on the MAF sensor, O2 sensor not working perfectly. Could probably get the fuel system cleaned, injectors etc. Try running some injector cleaner in the next tank, there is also a cleaner for the MAF sensor, talk to your auto parts store. Cheers.

SteeleHorse · Posted: Wed Sep 03, 2008 3:15 pm Post subject:

123ford · Posted: Wed Sep 03, 2008 4:23 pm Post subject:

Put injector cleaner in all my vehicles from time to time, never had a problem. However I agree with SteeleHorse get the whole system flushed properly. Good point there Steelehorse.

aksival · Posted: Wed Sep 03, 2008 6:36 pm Post subject:

Thanks everyone. Obviously, it's not a huge problem but if it keeps up and the MAF cleaning doesn't work then in the next day or two I'll take it in for a closer look.

Any chance that, if a sensor is not working properly, it would show up when they run the electronics test?

ezzigsxr750 · Posted: Sat Sep 13, 2008 11:44 am Post subject:

I have these problems with my truck. I as well changed my battery before they started. They did seem to get worse over time. My truck now stalls out when I come to a stop, it happens more often when the a/c is running. I have been searching threw the posts here and other sites and have read this exact problem numerous times even with the battery change but I have yet found the answer. I am hoping that someone has had this issue and resolved it or someone knows the answer to my problem.

Thank you, Robert L.

aksival · Posted: Sat Sep 13, 2008 12:37 pm Post subject:

I did notice that, if I turn the A/C off, the problem seems to go away. I haven't noticed it that much in the past few days, however. It seems to be fine for the time being. Weird.