Possible problem with a well known tuner. Your input is welcome
I had a well known and highly regarded tuner (known to this forum) sell me a tuned PCM for my car. I only had one made to get the speedo to read correctly, and I kinda also wanted a spare sitting around. The one that was in the car works great - it just reads fast.
So I get the PCM from the vendor, and immediately notice the idle is 800-900 RPM's in park - hot. (The car is an A4) And 700 or so in gear. Both of these are high by 150-200 RPM's. The idle also was a little rough, and there were some pops in the exhaust, almost like a misfire/stumble. I drove it like this for a day, and it also got much worse MPG.
I got home and put my old PCM back in, and all of the problems instantly vanish.
I reached back out to the vendor and he tells me that the pops in the exhaust and the high idle are surely signs of a vacuum leak, and its not his tune. I tried to tell him that all the issues go away with the old PCM, so his response was: "put in your old PCM and I guess you'll be good, then"
Before I lose my stack with the vendor - I have to ask: is it possible for one PCM to react to a vacuum leak and the other one ignore it? I've checked the car with propane as well as a vac gauge and everything appears normal. To my knowledge, there's no leak. But I'll keep looking if you all think this is possible
Last edited by AtlantaDan; 10-24-2015 at 10:49 AM.