I am working on a 1995 F150 XL 2WD 4.9L Automatic, I have no error codes. I have checked the TPS, IAC and EGR. All are functioning properly with the transmission in park. The idle speed is correct as well as the TPS voltage output at idle.
With the vehicle in park the engine runs fine. When I put it any gear the engine RPM decreases, usually to the point of stalling. When it does not stall the RPM will the increase slightly to a normal idle.
Any ideas?

Larry

 

Sounds to me like a worn out IAC, they don't usually give codes when they go bad, at least not on that era of vehicle, I also seem to recall those systems having issues with the throttle body and repair meant changing it. IAC is considerably cheaper.

Without looking at live data it's hard to say otherwise, those are just some things I remember from my dealer days.
.

 

Thank you Rnlcomp!
The IAC has been replaced.
The problem has been narrowed down to bucking and stalling ONLY the vehicle starts to move. It runs fine in park and in all gears with the brake (emergency or pedal) on. As soon as the brake is released and the vehicle moves it starts to buck and then stalls.
Larry

 

Hmm I wonder if the torque convertor is locking up before it should or stuck locked up, it would certainly create the symptoms you describe. Again, need to monitor live data to be sure.

Not going to guess this concern away.
.

 

Here's a vote for the torque converter.

 

Thanks to all,
I guess I'm going to learn all about automatic transmissions. I'll keep you posted.
Larry