Need help from the experts. My f-150 just started having a problems idling a few weeks ago. When I start the truck up I notice that
the battery gage swings back and forth and the engine acts like it wants to stall and then will return to normal idle. It will do this for a couple of minutes and may actually stall. I also notice the headlight will get real dim and then brighten again as well. Do I have a sensor problem or something more serious? Thanks in advance for your help.

 

What model yr is your truck , How many miles on it ? It sounds like you have a alternator and or battery problem .

 

My truck is a 1994 with 90k miles on it. I was thinking that maybe it was a sensor on the throttle body. I looked at some other posts with similar problems and they talked about takein off the throttle body and cleaning the carbon build up thouroughly

 

Yes , Cleaning the Air Bypass Valve , which controls the idle speed & cleaning the throttle plates would be a good first step .

 

Yes...the throttle body cleanup would work, if he was just stalling. But he says his battery gauge is changing. I'de say alternator problem. use a multimeter while the truck is running and check the posts of the battery and the alternator wires to see what the output is. it should be about 12-14 volts when the truck is running...i think that is about right?? if it is lower, replace the alternator...