Check engine light?

About 6 months ago my car stopped working, the car would just stall dead, no notice, turned out to be a "spark plug relay" or something like that where the car was not sending spark signals to the engine. After I had that fixed the check engine light would come on, at first it would come on every 2-3 times the car would turn on and would remain on until the car was cold, it eventually turned into an all the time thing, had the car scanned and came up with "long cranking code" they reset the computer and it went away for sever weeks then started all over again. They then recommended a level 2 service, the cleaned the fuel system, chenged the oil and did whatever else they did for nearly 300 bucks, the light still came on. But only one the car had be on and warm and only every 6th-7th time the car was turned on. Since then i've replaced the battery, starter, exsaust pipe and muffler and for a short while the car ran fine. Then it would only come on after the car was turned off and back on from driving it for at least an hour. Now it's back on continuously. When the car has this check engine light on the car hesitates horribly, loses speed going uphill guzzles gas and idles really roughly. The engine also heats up quite quickly compared to when the check engine light is not on it runs perfectly. Well as quickly and well as a 3 speed auto can. What's wrong with my car? The mechanics said tune up did that, still does it, they said it's old, it's got like no miles on it and when the check engine light isn't on it runs perfectly. Thanks!

I used a paperclip to short that wire on teh diagnositc accroding to the directions. It reported 3 times code 12, then 3 times it did code 42(four blinks pause 2 blinks) according to the sheet
42- Electronic Spark Timing (EST) bypass circuit, or EST
circuit open or grounded.

Whatever that means. Thanks any help would be great!

My son has a 1991 Grand Am that runs fine, once it's started. It has been experiencing problems starting for the last six months. Details of the problem:

1. The engine starts hard, cranks multiple times for maybe 15 - 20 seconds.
2. The fuel pump and filter were replaced last year. Don't know how to check fuel pressure.
3. At 100K miles the injectors were replaced with rebuilt units.
4. The check engine light is not on.
5. The plugs look OK, all tan in color.
6. Good compression on all cylinders, does not use oil.
7. Seems to start better if throttle is held slightly open while starting.

Would appreciate any help.

My grand am check engine light comes on if the car is in park or at an idle and runs rough. If I turn the the ignition off it resets or drive it for a while. I've tried jumping the ab terminal and can't get a code to pop up. Can anybody tell me what wrong?