My '88 240 has a problem with stalling. The problem seems to be heat-related, as it first appeared during the early 90+ degree days this summer. When accelerating from a stop, the engine acts as if all fuel flow has stopped for a split-second - tach drops below 600RPM, then picks up again. If I press the pedal to the floor, it will also pick up. This will also occur when cruising at 2000RPM or less, and the engine has to be up to operating temp before it happens. When I drive the car to work at 7AM, it doesn't stall. If I let it sit for a few minutes and start it up again, it will stall. The tach never drops to zero, so it seems to be a fuel system problem, rather than ignition.

I've replaced the fuel pump relay, cleaned all of the grounds, checked the main fuel pump fuse in the engine compartment and cleaned the fuse block inside the car. I've also cleaned the electrical connections on the AMM, the knock sensor, the coil and pretty much any other connections on the left side of the engine. The car also has a new cap, rotor and coil. I've pulled the in-tank pump, cleaned the "sock" and used some Techron injector cleaner recently. The O2 sensor is about 2 years old.

So, at this point I'm stumped... The only other components I can think to check are AMM, fuel pressure regulator, the actual fuel pump and the fuel filter. Any help you could give would be greatly appreciated.

Thanks!