1990 f150 Will allow the code reader to do the engine off test, but when attempting to do the engine running test it almost kills the motor and the comp. goes into some kind of safety mode and won't allow the reader to read it
This all started cause my engine will not rev out after it's sits for a minute off. When I start it again and try to rev it, it flattens out and pops a little.
Now the funny thing is if I put it in drive and pull it forward 6" and yes 6 inches
Then put it back in park it will rev out perfect.
I've changed: o2 , fuel regulater and filter, egr and plugs& wires and distib button. Any help would be great.