98 Outback can't handle going downhill!

[clamshell4]

I've spent close to $600 trying to get a problem diagnosed with my 98 Outback wagon. I live in the mountains in Vermont and much of my driving involves hills. Uphill is fine, long gradual hills are another story. The engine light comes on and the car has a tendency to run very rough when I get to the bottom of the hill. Restarting it solves the problem. I have changed the plug wires, battery, gas filter, etc. Someone suggested cleaning the battery terminals after the car stalled during one of these downhill events. That seemed to make it better temporarily.

 

Last week I stopped for gas. The gauge showed that I had more than a 1/4 tank. It took 13 gallons to fill so I realized that the gauge is wrong. I thought that maybe I was unknowingly running it with very little gas and it was somehow screwing up on the downhills, but now the tank is full and there are still problems.

 

I took a trip recently and drove 1000 miles and had no problems because it was flat. Other than moving, any ideas?

[MorganM]

Hmmm thats a wierd one!

 

YOu said the Check Engine Light comes one (CEL) have you pulled the code(s) to see what is throwing an error? Even if the light shuts off the code is stored in your ECM and can be retireved.

 

I would start there

[blitz]

Are these "gradual downhills" actually mountain grade descents where several thousand feet are lost after being gained? If so. I'd have a look at things that are affected by changes in atmospheric pressure, like the gas cap, evaporative emmision system, atmospheric pressure sensor, and possibly the fuel pressure regulator.