Dodge Repair: Bucking, coolant temp, crank sensor

Question
Ok I have a 1994 Dodge Caravan SE with a 3.3 v6 engine and I am having problems with bucking. I have replaced the TPS, Map, O2, Coil pack, spark plugs, wires, crank sensor, coolant temp, fuel pump,alternator,injectors, Engine controller, and alot of money. now this only happens when engine gets hot or a 1/2 hour after driving (sporatically while driving). I haven't replaced the cam sensor, AIS, speed control switch, distance sensor charge temp sensor or knock sensor.Also my fan is not kiking on even after replacing sensors and relays. took it to a mechanic and computer does not read any errors. Help! Please!

Answer
The mechanic needs to hook up the computer and check other readings than simple fault codes.  There are cylinder misfire screens that can tell you which ones are not firing properly.  Also, a fuel sample may show something such as debris in the fuel or even water.

There's a couple of electrical connectors under your battery tray area that get covered in battery acid.  This would be something to check.

Also, it's hard to beleive that after acting up the way it does there are no codes.  The dealer has a scan tool that can show how many starts have been made since the memory was reset.  This is valuable information when trying to determine intermittant or no-code related conditions.

While you have replaced alot of components on this vehicle I would also come to the conclusion that your money would have been better spent having someone qualified actually diagnose the car and fix it right the first time.  Many of the components you mentioned CAN cause the problem your having but as you have painfully found out they can also NOT fix the condition.  I would suggest having someone more qualified take the car off your hands and let them do what they do best.
Doug