This is another good response from Dr. Loot, 99 percent of the time (I pulled a high number out of my head, not an exact figure) a drivability problem without fault codes it is fuel related. As stated, check the fuel pressure (9 to 13 psi) to be sure it is in the needed levels and replace the fuel filter. Is this a new symptom, was it acute (come on all or a sudden) or has the condition continually get worse?
When you check the fuel pressure be sure to check it when the engine is warmed up to match the conditions when the engine acts up. Also leave the fuel pressure gage hooked up after the test to check for fuel pressure bleed off. If the fuel pressure bleeds off more than 5 pounds or so with the ignition off, this is an indication of a failing fuel pump.
Another thing to check is the distributor main shaft and the gear at the bottom of the main shaft. I have had several vehicle with hair line cracks running the legth of the main shaft. This generally causes a loss of power under a load, the cracks allow the shaft to twist under accelleration, and causes a loss of power under load. This is due to the timing being retarded, caused by the shaft twisting, and does not set a check engine light, so this is a possibility I would check out.
The gear at the bottom of the main shaft being worn causes the engine to cut out and a loss of power under a load. This condition will normally set the check engine light with a cam or crank sensor code. Therefore, I don't feel this is your issue, but if you have the distributor out and apart to check the shaft, with your mileage I strongly recommend a quick look at the gear as well.
You stated that you have changed every sensor except for the VSS, did you have fault codes to point you to these sensor or were you putting parts on in hopes of fixing the problem? If you had fault codes, what were they? A fault code does not alway mean the specified sensor is bad, it may just be the sensor that noticed the problem.
Get back to us and let us know what you find, we will do our best to help you out.
Saturday, March 6th, 2010 AT 1:48 AM