My truck has been recently possessed! I have a 97' 150 XLT, 4.6, 4x4 off road package, 5-speed manual trans, 33's for the tires.

I know that my brushes are going out in my alternator (120,000 on the original alternator). When I run the engine upwards of 4.5K before I shift the charge light will flicker on and the lights will dim. This I know for a fact......The question I have is the truck is beginning to miss......could this possibly be related. I am planning on replacing the alternator this weekend, I was just hoping that I would not be looking forward to any more repairs.

If anyone has ever experienced missing out of thier 4.6 because of a bad alternator it would really put me at ease.

Thanks

 

Address one problem at a time.
The brushes begin to float from being worn down short and comutator out of roundness.
It may be generating enough spiking to affect the PCM.
If it fixes the miss, fine, but don't count on it.

 

Thanks....I think I plan on tackling the alternator, then the plugs, and a new belt while I am in there this weekend. We will see what happens.

 

I had the same problem happen to me in '01 and had misfires happen about 4 times. I own a 98 F150 XLT and then I noticed the alternator (voltage) light come on at high RPM's. I changed out my plugs first, but it wasnt the problem. Once I figured out the alternator wasnt creating power at high rpm's I removed the alternator and 1 brush had prematurely wore out (probably from being installed wrong or ****eyed). Had the brushes replaced and I have not had a misfire since. Pretty sure that the brushes not contacting the rotor was why I had misfires with the check engine light coming on.

Hope this helps.

 

Sounds like you need brushes, about $10 but an hour to install. Cool motor makes it much easier.

 

This sounds pretty familiar, and if it's what I'm thinking, your alternator is cooked. My buddy's 98 would act weird like this and it turned out to be the alternator. Seems logical, a good place to start anyways. Good suggestion, use silicone dielectric grease on any exposed electrical connection, ie. your battery posts. I'm still on my original batt, from Nov.99. My starter also got greased, twice now on the terminals. Anything that can corrode. Betcha it's the alternator though.

 

Thanks everyone for the advice.....I changed the alternator and it solved about 40% of the missing and the charge light comming on at high RPMs. However I still had a miss in there. With the engine running I took a spray bottle of water and put a fine mist on the plug wires and guess what.....I had spark! Unfortunately it was on the outside of the wires Sooooooooo I ended up having to replace the plug wires and while I was in there I went ahead and changed the plugs. She runs like new now!

Thanks again everyone