M103-Fuel Pump/Ign. Coil Question

[Mike Murrell]

I reported a problem here a week or so ago that I thought was related to the addition of a can of snake oil in the gas(Berryman's Chemtool B-12). After 30 mi. or so of highway driving in near 90 degree heat, the car would not restart after sitting in the driveway for about 10 mins. After 10-15 mins of cooling off, car restarted, but idle began bouncing up and down from 300-1500(approx), then would die. Once fully cooled off, the car started fine and ran ok.

Last night on the way home(another 30 mi. drive on the highway), the car began to cut in & out after about 20 mi. of driving. I suspected the car was going to stall when I pulled off my normal exit, so I chose one a little further down with less traffic & that was a good idea as the car died when I came to a stop.

The vehicle did as before when I cranked it - nothing. Engine would spin quickly, but no hint of wanting to start. I walked home and returned and hr. later. Car fired up and I drove home(3 mi. drive). Once inside the garage and at idle, the idle speed began to jump up and down and the engine died.

OVP and MAS controller(contains fuel pump relay) were replaced about 1 yr. ago.

I realize there are a maze of things to check such as:

- Throttle Valve Switch
- Idle Control Valve + hose
- Vacuum hose under int. manifold
- EGR
- Crank Position Sensor
- Air Flow Pos. Sensor
- Decel Switch

In both cases this has occurred when it was warm outside - car had been sitting in near 90 degree heat all day and driven home in temps not much lower than that. On cooler days in between the first occurrence last week and last nights reoccurrence, this has not happened. In all cases, the temp gauge never goes much over 80C.

I'll check the list above, but am somewhat doubtful it's vacuum related. If I had a leak, it seems the problem would occur irrespective of the ambient temp?

I've read that heat can affect the secondary side of an ign. coil - suspicious of this part and was wondering if it could also impact the single fuel pump my model has? This unit is the original Pierburg pump. Fuel filter changed about 10,000 mi. back.

Have also noticed that I'm getting much better gas mileage than I usually do. The tank is just a little less than 1/2 full, so I haven't refilled & calc. mileage, but after hitting the 1/2 way mark, I had driven about 250 mi.. Normally I've driven about 210-230 mi. when the 1/2 way mark on the fuel gauge is reached. This would indicate a lean condition or a miraculous improvement brought on by the snake oil.

Thanks for your time.