I have the infamous 4.2 v6 in a 97 F-150. A friend was using it temporarily and he reported a slow (over a month's time) decrease in power until it will just barely start and has to be babied to get it to almost idle speed. Only codes on the scanner were 1537/38. Checked IMRC system, all checked out. Can't get any more codes out of it because it now won't run long enough to throw a code.

Scanner shows 90-100% engine load and timing retarded 2-10 degrees while running.

I've seen references to crank pulley slipping off key/keyway, but is there any way to check cam/crank relation similar to the old school gear marks or TDC on cyl 1 vs crank location?

Any help is appreciated.....

Also seems to be next to no vacuum on the intake manifold port.

 

I'd 1st clean the IAC and the throttle body. Changing the fuel filter would also be on the "to do" list as well as replacing the PCV...Oh yeah almost for got change the air filter. Start with simple things and then work your way up to maybe odd stuff like the slipping on the key.

 

been all through the simple stuff. filters, pcv, iac, plugs, coil, wires all check out or are new. fuel pressure good. fixed some vacuum leaks (egr solenoid, imrc solenoid).

 

Moved to correct forum. You should get more help here.

 

harmonic balancer broke, shifted on the crank.....

 

When a harmonic balancer fails, does it make a rattling noise? I have a 97 F150 4.2 which is oem pretty much on everything. Thanks.

 

When I had a 97 with the 4.2 it threw the same codes.I had to have both IMRC parts replaced.Do a search on here and you will find my post.