Hi I'm a newbie to the forum and would like to share the journey to fix my 2000 986 which was suffering from rough idle/limp mode issues. The car was diving great the night before and was parked in the garage as usual. The next morning when i tried to take her out the Idle was all over the place and I couldn't get over 2000revs so I jumped onto google looking for answers. The general opinion was to replace the coils and plugs to cure the rough idle, I never drive her in the rain but I had got caught in the rain the night before and thought that it was possible if there were hairline cracks in the coils water may have got into the coils causing the rough idle so I replaced both the coils and the plugs. Still no change, so back onto forums I went, If you disconnect the MAF sensor and the car runs better then you need a new MAF sensor, I tried cleaning the sensor but still no change. A new MAF sensor was ordered and in the meantime I ordered an iCarsoft POR 3.0 to see if there were any codes as the CEL hadn't come on. I fitted the new MAF sensor but STILL NO CHANGE. By now I'm getting a bit frustrated and thinking the solution might be a gallon of petrol and a box of matches but on I pushed. The scan tool arrived and I was able to get a code from it, P1502 Throttle jacking unit,spring test-above limit. Google is my friend, turn ignition on for 1 min, turn off for 10secs, turn ignition on. Yeah you've guessed it still no change. Next cab of the rank is to remove and clean the throttle body which was done with no improvement so now I'm trawling all the forums, you tube video's, witch doctors, clairvoyants anything to try and solve the problem. Then I stumbled on a forum where someone had exactly the same issues I was and he traced the fault to his ignition switch, he realized he couldn't hear the throttle move when he turned on his ignition and instead of troubleshooting the throttle body he concentrated on his ignition switch. His solution was to turn the ignition on and off quickly 20 times and then start the car. Surely not but hey I'm willing to try just about anything by now so off I trot and would you believe it I've got my baby back and she's running as smooth as a swiss watch. I hope that this helps anyone else who finds themselves in the same situation.

 

This is almost certainly bad coil(s). Replace all of them and you will likely be good to go. I went through this with my 981.