Lazarus-F150

I've got a 1992 F150 4.9L 4x4 and have been having a screech on start-up (ranging from ~1 to a few seconds). At the same time as the screech the CEL lights up, but then goes out. I don't know if any of the following may have led to this issue, but here's a recent history before this started happening:

1.) replaced 2G alternator (after having it catch on fire while I was driving) with the RJM 3G alternator and wiring harness kit. The new alternator has a 2.25 inch drive pulley instead of the stock 2 inch size. After doing this, I started hearing a screech on start-up and I just figured that I stretched the serp. belt while I was changing it out.

2.) While doing some other maintenance I noticed that the PCV intake filter had disintegrated, so I replaced it. Immediately after doing this the CEL came on and stayed on.

3.) A couple of days later the CEL stopped being on all the time and just started briefly coming on as the engine was turning over and then turning off within a few seconds. The CEL was coming on at the same time as the screech as described above.

4.) Since I just expected that it was a loose belt issue, I replaced the serp. belt, but I'm still having the same problem.

Any suggestions?

Thanks

sylver91

Screeching makes me think the tensioner is bad, but the extra .25" on the belt is making it tighter so you may have to swap back to the 2".

To find out why the CEL is popping up you will have to pull the codes to pinpoint whats wrong.