Ok so after Saturday's cooling system flush and no start, I went out on sunday and cleaned the throttle body, checked all sensor/electrical/distributor connections that I could find, took off the intake hose and checked for holes (none), checked all the connecting hoses and used a bit of electrical tape to temporarly patch some cracked (but not completely cracked) hose bends, put a new airbox thermostat in (old one was nasty), replaced all vacuum hoses, and then did a tranny flush/fill (unrelated but it needed it!). The test drive started out extremely smooth with the engine running better than ever! Everything was going well until I hit a jarring bump and the damn engine light came on and went off again, partially stalling at the same time (still can't find that loose connection but seems to be in the front somewhere). I was then stopped at the light and the car began to cycle from about 1200 rpm down to about 500 rpm while in idle. I had to hold my foot on the gas to keep it from completely shutting down. I pulled over immediately after the light changed and discovered that I forgot to plug in the Throttle position sensor plug (thats the one in the throttle body, correct?). Once I plugged it back in (with the car off) the car started fine but was now running the same way it had before all the tb cleaning and hose fixes - a slight surge at idle (rpm needle bounces up slightly around 750 rpm). Argh!!! Any ideas on what happened? Do I need to reset something because the TPS wasn't connected, or is it possible that the sensor is dead? I have an 88 240 parts car - would its TPS sensor work on my '90 wagon? I'm wondering why did the idle not act irratically until after the big bump/engine light/stalling thing? We had been driving for about 20 minutes with lots of lights(stops) at that point. Any thoughts are welcomed. Anything to worry about when swapping out these switches?

Also, more related to the stalling/engine light coming on when hitting large bumps, could this be related to a bad or loose knock position sensor? If it is jarred too much and is loose or installed incorrectly, could it cause the engine light to come on and stall momentarily?

BTW, the car has over 256,XXX km's... maybe these sensors are just worn out?

Thanks,
cton.