My 93 F150 has the 302 in it. When I put my truck in park after its been driven the voltmeter on the dash fluctuates as well as engine rpm. I'll note that this only happens sometimes. Everything returns to normal after the gauge moves back and forth a few times. As far as I know this only happens when I go from drive to park. And usually after this occurs, when I go to start it again after its been off it won't start on the first attempt. The second attempt does the trick but I have to hold it for at least 4 seconds and even then it stumbles to start up.The starting issue does not always follow afterwards, it'll sometimes do it without the fluctuation of the gauge, which makes me wonder if two issues are related or not. I checked the battery and alternator and they both read normal. 12.2V for the battery and 14.4V for the alt. Any clues to what the problem is?

 

Pull the distributor cap and put a socket and break over bar on the crank shaft. Have a helper watch the rotor as you turn the crank pulley. Pull one way and have him check to see if the rotor moves immediately. Then turn the crank shaft the opposite direction and see how far it maves before the rotor begins to move. It is possible you have excessive slace in the timing chain.

 

Could have something to do with the crappy 2G alternator causing your voltage fluctuations. Research 3G swaps, and also pull the OBD1 codes.

http://oldfuelinjection.com/?p=13

Adrianspeeder

 

your voltmeter could be fluctuating because the engine rpm is, this could be because an air pump not running well or maybe your iac but i guess the air pump (put a shorter belt on it bypassing the pump and test it.

 

I'll check for slack in the timing chain. I was planning on replacing the alternator when I get the new stereo and speakers. For now the alternator seems fine but maybe ill replace it sooner since the 2G's are crappy. As far as the iac goes, I had work done on that not too long ago. If the air pump is part of the thermacator air system, I had that checked out the last time I took it in for repairs and that should be ok. The check engine light came on months ago and I haven't seen it since. I pulled the codes back when it showed up. It had to do with the EGR valve not properly opening or closing. I didn't think that the EGR would have to do with this issue especially because I haven't had any further problems with it.

 

I had a problem like this and it turned out to be the connector and wiring on the alternator was fried, making intermittent contact. The engine rpm fluctuated and the voltmeter bounced around.