Engine Performance problem
1993 Toyota Corolla 4 cyl Front Wheel Drive Manual
A couple weeks ago, my car started hesitating once it got to its normal operating temp at slow speeds. It was intermittent, mostly when I was accelerating from a stop. When I tried to accelerate, the rpm's would fall to around 200 to 400, with no shaking or backfiring. I'd really step on the gas, it might creep forward a few inches, stop, creep forward again, then the rpm's would jump up and my car would take off like nothing was wrong OR it would stall. When it stalled, it would start right back up usually, sometimes stalling again or would drive like there's nothing wrong with it.
The problems gotten a lot worse. My car reached normal operating temp on the highway and the rpm's suddenly dropped off, but picked back up again. Once I got off the highway, my rpm's would drop off every time I'd slow down, and my car would try to stall out. Once it stalls, it won't start until my car's had time to cool off, and won't run unless it's cooled off for at least 45 minutes.
Now this happens every time I drive it and it gets to its normal operating temp. If I'm in traffic, the temp will creep slightly over it's normal, and I start having trouble.
I've changed the distributor cap, rotor, spark plugs and wires, air filter, fuel filter, and coil out a few days ago, and it hasn't helped. The fuel pump is only 6 months old. I've checked for vacuum leaks, and taken a look at my PCV valve, pressure regulator valve, lines, etc.