Hello, I have a 92 MAZDA MPV V6 3.0 L Automatic. It has about 145,000 miles on it. The car was running fair, OK. I recently changed the timing belt. After that, I discovered that when I go up on a 'deep' hill, it is really lack of power. No matter how hard I step on the gas, the car only goes about 20 mph. (Even when I shift to 2nd or 3rd gear.) One time I was on a freeway and on cruse control, the engine has to go up to about 5000 RPM to maintain the speed about 60 MPH (it was uphill.) I turned off the cruise control and keep the engine about 3000 RPM, it drop back to about 40 MPH or less. On level roads, the car has no problem going up to 70, 80 MPH. It only has trouble when it goes uphill. I also check the compression of each cylinder, all the passenger side (cyc. 1, 3, 5) have about 145; the driver side (cyc. 2, 4, 6) have only about 125. Other than that, the car is running fine. Don't know whether it is the engine has trouble, 'one side of valves off after timing belt change?' or is it the transmission having trouble? Please help.

I didn't have any old record but not sure whether the compression when up to 145 before or not. If I'm off when aliging the timing belt, will the cylinders gave higher than normal (about 120) when checking with pressure gauge? There is no back fire or after-run. I can also feel the van shift gear about 20MPH and about 30 MPH, any idea? thanks in advance!!

Sounds like the left camshaft is off by a tooth or so. Should show up with a check of ignition timing and timing light as the distributor is run off of the left bank or drivers side camshaft. That side cam is a bugger to line up anyway as you practically have to stand on your head to see the alignment marks. Helps quite a bit to pull the air cleaner housing.