The hesitation is not much just a slight one and is not present when the engine is cold. I already replaced the oxygen sensor but this did not fix the issue. Let's say I am driving with 40 m/h on the highway and press the gas pedal to accelerate, the hesitation will occur somewhere in the 1/3 of the gas peddle range. If I release the gas and do it again it will do it in approximately the same spot and I can reproduce it. Fuel filter was replaced, plugs, wires, rotor, dist cap... If you have any advice it is very much appreciated. Thanks

Possibly coolant temp sensor. More likely its the TPS ( assuming that this is a fuel injected engine). TPS could be out of adjustment , or just plain worn out. Also possibly dirty fuel injectors, or the AFM door sticking.

Just some places to start looking.

Mike in aR

It is fuel injected - where is the TPS located. I looked at the book I have but it doeas not show it (or I can't find it). Thanks a lot!
How would a coolant sensor affect this???

The TPS is located at the entrance to the intake manifold. It's on the outside and attaches to the shaft that holds the butterfly inside the throttle body. The other end of the shaft is attatched to the bell crank -- where the accelerator cable is attached. Proper operation and adjustment of the TPS is very important to overall engine and transmission performance.

Temp sensor tells the ECM (computer) when the engine is warm enough to switch into closed loop. When the engine is cold and first started,, the ECM gets a signal from the temp sensor and puts the engine in open loop-- that's a preset condition so the engine can run while it's warming up.. If the ECM doesn't know the engine is warm, it won't switch to closed loop and you can get poor performance.

Mike in AR

I tried everything - disconnected the TPS - no difference! Disconnected the collant sensor and it still hesitated but it was a little different flavor of hesitation. I hate to take it to the dealer but I may have to. One independant shop wanted 180$ just to diagnose it. Thanks