Tricky light

I drive a '95 Ford Probe (2.0L, manual, 124K). I’ve had almost no trouble with it until recently. About a year ago, the “check engine” light started coming on as I accelerate thru about 45 mph on the interstate. A few seconds later, it goes out. I took it to the shop, and they said they couldn’t diagnose it because the computer doesn’t hold the code(s) once the light goes out. Now, it’s coming on more frequently, like when I climb hills, and staying on longer–but it always goes out after about 15 seconds. Any ideas? Could it be compression-related?

Your shop is wrong … as far as I know ALL computer codes are saved (unless the battery is disconnected). You can pull the codes yourself:

No joy. I followed the link, printed the instructions, and headed out to the car with a wire. I found the right terminals, shorted the ground to the TEN pin, and switched the ignition to ON. The CEL came on steady and stayed on (as it normally would when the engine isn’t running). No blinking. No code. Anybody got any ideas?

A CEL that goes on and off, usually under acceleration, means you may need a tune-up. This is sometimes a ‘mis-fire’ indication. When was your last tune-up?

My last “professional” tune-up was >8 years ago. I do my own minor mx, but I’m no expert. The oil gets changed every 3k. Car consistently gets 30-31 mpg in “mixed” driving, 34+ on highway. There’s no noticeable roughness or loss of power with the light on or off. The plugs have about 30k on them now, but the light’s been coming on for about a year.

Sep 08 (116.0k): coolant change
Jul 08 (112.7k): cap & rotor
Jun 06 (93.5k): plugs, PCV valve
The spark plug wires were changed sometime between 06 - 08.