Here is my problem. Every so often, maybe 3 times a week, My SES light will come on and my tach shudders for a moment. I can feel the car is lacking power. The SES light will shut off sparatically and the tach shudders again and the engine has full power. When the SES light is on it feels like something is clogged and the engine just cant perform right. Here's the funny part. If I shut my car off when the SES light is on and I restart it, it will stay on until what ever it is causing the problem fixes itself and it will go out. If I shut the car off with the SES light on and do a diagnostic check it only displays code 12. When I turn the key off and start the car again the SES light goes off and the car runs fine again. This problem is more annoying than anything else right now. I have had this problem about 2 months now. I know it is not anything clogged in the exhaust system because I just completed a header install, neew cat, and 3" pipe all the way back. I have good plugs, wires. I replaced the cap, rotor and coil about 6 months ago. Pcv valve is new. AIR pump works. What can be doing this? I appreciate any help.
Tony

 

Have you tried doing a diagnostic while the engine is running? If you do this and still get a code 12 then it might be a problem with the distributor reference signal. At least that is what an old Chilton's manual is telling me. I have done this with my own car and not gotten the code 12 while it was running.

 

It wont pull a code while it is running. It just keeps the SES light on constant. The ignition module went out last December and I had to replace it. I have also replaced the cap, rotor and coil just for maintenace and tune up purposes.