i have a 1999 dodge caravan 3.0. when you start it up it idles fine.
when you push on the gas it back firers in the engine. when you put
it in drive and start to take off it will start to take off but when you
press a little more on the gas its does not seam to want to go any where
it will barely even pull up a hill. At idle it runs fine when i turn on the
ac it kills the engine. it just does not have the power to do any thing it barely will get up to thirty with the gas on the floor. These are the items i have all ready replaced trying to locate my problem.
1- timming and timing belt, catalitic convertor, spark plugs, spark plug wires, computer pcm, o2 senior, basic tune up,ari filter ect, fuel filter,
transmission fluid and strainer, all 6 injectors, distributor, .
If any body has any ideas please let me know. I need help.

your egr valve may be stuck partially open. try changing it

Why haven't you taken it to a dealer and had the sensors checked? Sounds like you have a sensor problem to me, possibly MAP or TPS. Replacing pieces without knowing the problem seems like a waste of a lot of money. My Grandpa had a similar problem and it turned out to be the MAP sensor, $50 for the sensor and $80 dollars for diag and labor sounds a lot cheaper than the method you are using.

if any of the sensors were bad, he would have got a MIL and a DTC

neon rt makes a good point about getting the vehicle checked. Although the local mechanic will probably give you a better price than the dealer. Have you checked the fuel pressure or done a compression check on the vehicle? It is possible that the backfiring is being caused by a burnt valve or other internal problem that a compression test might identify. Also check the fuel pressure to see if it is within specs. Low fuel pressure can cause a lack of power as there is not enough fuel being introduced into the engine to allow it to run properly. If the pressure is low it can indicate a bad fuel pressure regulator or fuel pump.

I suspect it may be the trottle position sensor. Teh idle will be fine due to the idle speed motor. If it was the oxygen or egr it would still have power but shitty gas mileage.

i have a 1999 dodge caravan 3.0. when you start it up it idles fine.
when you push on the gas it back firers in the engine. when you put
it in drive and start to take off it will start to take off but when you
press a little more on the gas its does not seam to want to go any where
it will barely even pull up a hill. At idle it runs fine when i turn on the
ac it kills the engine. it just does not have the power to do any thing it barely will get up to thirty with the gas on the floor. These are the items i have all ready replaced trying to locate my problem.
1- timming and timing belt, catalitic convertor, spark plugs, spark plug wires, computer pcm, o2 senior, basic tune up,ari filter ect, fuel filter,
transmission fluid and strainer, all 6 injectors, distributor, .
If any body has any ideas please let me know. I need help.

Sure the timing is correct on it ???