I am having a similar problem I believe to some other postings. I am getting something like a misfire or more like the a gremlin switching off the engine for a split second at just over 4k rpm when cool. As it warms (block temp not water) the misfire/ bucking drops down in RPM to just over/under 3K and becomes more pronounced, IE 500rpm drop on the tach. Engine seems to runs great under the 3k RPM power seems good etc. Plugs, wires, FF, AF changed. Also swapped out coil for new unit with no effect. No check engine light and no codes, and yes PCM will toss codes (checked it by disconnecting a sensor). I am beating my head against the wall..................Help please.

 

Is there also a speed relation to the bucking as in trying to maintain a certain speed? It could be a DEAD spot in the TPS which causes the PCM to tell the injectors to back off on the fuel delivery. Easiest way to check is to disconnect the TSP and drive the vehicle. It will set a code for the TPS. Also remember, you cannot tromp on the gas as the engine WILL die as the PCM will not know where the htrottle is at and not deliver enough fuel to catch up. Take it easy and see if the problem goes away.

 

Tried that, also tried it with MAF. This morning noticed sharp sound as if belt was stuck instantly but more of metal on metal, as it started to do this in park at about 3k rpm. The sound came from the rear of the blockI am thinking that the syncro is having a problem. Ever heard of them having intermittant failure? I had a couple of guys at work listen they agree that it is not a misfire, it is more like the ignition shuts of intermittantly............This banging my head against the wall and it is starting to hurt.......Thanks for the ideas and input please keep tossing them out.

 

Resolution........The Ford Taurus, Sable and Rangers from 2000 thru 2003 can have a hesitation bucking over 3000 rpm due to the syncronizer. No trouble code will display as the fault circuit for the cam sensor is not monitored over 2500 rpm per Ford TSB. To determine that the syncro is the problem the knock sensor is monitored, it should read 125 or less if the syncro is bag it will register several hundred to it's limmit of 1023.