Sparrow

97subaruGT, Sorry to hear about the problems. I recommend you first ensure the grounding is in order. Check the contacts at the battery terminal and the ground points on the car. Perhaps add a couple more ground wires (8-10 gauge) to the intake manifold, and see if that smooths things out. I did it on mine, and it is much less rough on accelerate and idle. Then if electrical sources are solid, you can confidently diagnose the rest (MAF, solenoid, etc). Check for air leaks after the MAF. If air isn't metered it can mess up your fuel mixture ratios.

Too bad about these HG problems. I just posted on another thread. http://www.ultimatesubaru.org/forum/showthread.php?t=19163 I fixed it myself. Both head gaskets. Cost me ~$300 CDN for parts and ~$50 CDN for beer. But to try diagnose problems, a leakdown test will show you if it is the gasket or block cracked. Bubbles in overflow mean HG is blown. A drop in pressure and no bubbles in overflow tank means the gas is escaping into the crankcase. HG is easy to replace, just needs time and a garage to do it in. The jack in your car is enough raise the engine up and to one side while you do one, then the other side the same. A good socket set and a breaker bar or two are needed, plus a good torque wrench. I am no mechanic, just mechanically inclined. I got some pictures if anyone wants to see.

It sounds very much like the problem I had...a leaking HG internally at the bottom edge of the #3 and #1 cylinders, on my '98 Legacy GT. Tiny Clark, the reason you don't see coolant in the engine oil and exhaust is because the leak is small. So, the hot gas can just squeeze through the crack, but the coolant, being a liquid not a gas doesn't make it back through the hole during the intake, before the next compression. If such a HG problem is suspect, look for an oily residue in the coolant reservoir, on the surface of the coolant and the inside of the tank. It won't be black, but it will look a bit dirty and kinda sticky/grimy to the touch. Also, look at the coolant level. If it is full in the reservoir, it may mean that the gases are displacing the coolant back into the tank. Your rad cap may have nothing wrong with it. Check for bubbles rising in your overflow tank, whilst the car is idling hot. Sure sign of head gasket problem. After I replaced mine myself in my landlords garage, the engine temp gauge doesn't move a hair once up to operating temp...and I often take it to redline. If you plan to tackle the job yourself, you may need to invest in about 30-40 beers to last you a long weekend! And a torque wrench.