Clearing faults with durametric caused a surge at idle

[steved0x]

I just got a Durametric to help me with working on my car (MY 2000 986 S, 105k miles) because I had been getting a CEL that would come and go ever since I bought the car several months ago, and around 2500 miles ago. When I checked my faults I had these:

P1117
P0430
P0507
P1130
P1128
P0139

(Interestingly no CEL, it was recently on during a drive back from FL but turned itself off on the way back)

The car is driving fine, the idle is most often rock steady around 675, but sometimes it fluctuates between 600-800 every second or two.

I cleared the codes with the Durametric and when I did the engine gave a little shudder and the idle immediately went up to around 1000 (maybe as high as 1200) and then it cycled between 700 and 1000 for a moment or two, before settling down at around 700. I am guessing that was because the DME was accomodating these faults somehow and when they were cleared it changed some parameters?

After I cleared them, I took about a 30 minutes drive, and the only one that came back was P1117.

The current MAF is around 40,000 miles/5 years old best I can tell from the service records (a couple of the records have only anecdotal date/mileage and this was one of them) so I think I will try cleaning it and see if the P0507/P1130/P1128 don't come back.

For the P1117/P0139, sounds like it may be time to change that sensor? From the records I have which go back the last 60k miles, only one of the precat sensors has ever been changed.

I have been checking the threads and there is some good information there; the only thing I hadn't seen was a surge in idle when clearing the codes on a running car (is that bad? I had the car running because I was checking out some real-time data streams from the o2 sensors)

Thanks!

Steve

Edit: One other semi-random thing. The CEL light does illuminate along with all the other lights when I crank the car, and it has come on and off a few times in the last 2500 miles, but when I commanded it to come on with the durametric it did not come on. I thought that was kind of odd.