what causes this?
truck in question is a 93 w150 w/magnum 318; mpfi

I thought mpfi was supposed to make things easier and make the truck run better. This truck has been an unending problem for the last 3 years.....

i recently got the truck running after several years of sitting; was originally parked for being undependable, running poorly, and eventually becoming unstartable....

fast forward ahead to now: truck runs OK at best. usually starts right up, and will idle good. if i rev it up, it will backfire when i let off, and the truck will usually drop to so low an idle speed the oil pressure will come on, and then it might recover or it might stall. truck seems to run good at high idle (2000rpm+). since i cant mess with timing, what are my other options?

truck has had the usual tune-up stuff done to it.

 

No codes?
Check injector flow,plugs,timing,etc.
Rule the working parts out one by one.

 

it should ahve thrown a code if its a sensor but id grab the haynes and start cheking all the sensors. does sound like timing though.

 

i cant adjust timing....the computer takes care of that...i cant move the distributer...or do we mean timing chain?

 

I believe you can check the base timing. The advance timing is done by the computer.