1996 Jetta GL
 

Need some help solving a problem. I have a 1996 VW Jetta GL, 4 Cyl 2.0. It seem that when my car is warm (normal operating temperature) it becomes hesitant when accelerating and the RPMs are between 3000-4000. I have not noticed this when the car is cold, or between any other RPM ranges. This only occurs when the engine has been running a while and only between 3000 and 4000 RPM. The car has 104,000 miles on it, and I recently had the timing belt, serpentine belt. This did not fix the problem and was told to replace the Mass Airflow Sensor (MAS). I replaced the MAS and it still has not fixed the problem. Any ideas before I sink more money into this car???? Thanks.

check your fuel injectors, fuel filter, and your engine temperature sensor (different from the thermostat)

If it's the ETS, then the ECU is not getting the message that the engine has warmed up, and is dumping too much fuel into the engine.