2004 F150, 4.6 V8. I'm wondering if my engine control module is going bad.

A few weeks ago I got into it in the morning, turned the ignition on, gauges responded as expected, warning lights on, etc. After starting the engine, all of the gauges peg to the left, and sort of "tremble", as if they were trying to keep going past the stop. After 5 seconds or so, they move up normally. This happens every time I start it now.

Since this weird gauge behavior started I have had to disconnect the battery to clean the negative terminal. After reconnecting it started experiencing idle problems. It idles smoothly, hitting on all 8, but it wavers. I found instructions in the owners manual for "relearning the idle and fuel trim strategy". It's been a over a week since doing this, and it still wavers and throws a P0506 error periodically, which I have been clearing. Twice while coasting the tachometer has jumped up to around 2000 rpm and the engine cut off, like maybe it thought the engine revved and closed the throttle to "slow it down".

Sorry if I'm long-winded, but my question is, have I just not waited long enough for it to re-learn to idle, or is it possible the engine control module is starting to fail? Any idea what a repair of this sort costs?

Thanks to any and all.

 

Is it the original battery? You might want to have it checked, if the voltage drops below normal it can cause some of these symptoms.

 

I agree about a voltage problem being the source of the problem.
Check the battery and have the Alternator tested.

 

It is the original battery, and I had intended to replace it and the negative battery cable anyway because of the age of the battery and the corrosion on the battery terminal. I hope that takes care of the problem.

Thanks for your replies.

 

Be sure to post what you find out.
Some people never let us know if we are any good at this advice stuff.

 

Sounds like battery to me also. These new Fords do weird things when batteries get weak or begin to fail. I had similar symptoms on my wife's 02 SEL Taurus and they went away with a new battery. Only she let it go to the point of it not starting before she told me.

 

Spot on, gentlemen, the battery. Tested at the Ford Dealer and it was only providing 126A (out of 650) for starting. They were surprised that the factory battery lasted as long as it has. The service rep asked me about the weird gauge behavior before I even mentioned it.

Anyways, new battery, no more chattering gauges, no more unstable idle, and they did the "Clockspring" recall repair while I was there.

Thanks all for your responses.

 

I'm glad all is well again.