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Hey everybody - I’m hoping someone can point me in the right direction here. I picked up a ‘96 850R a couple months ago and just finished up with some deferred maintenance (timing belt, water pump, PCV, oil change, new exhaust, new 02 sensors, new spark plugs). I took it for a quick shakedown drive after putting everything back together and it felt like the throttle was sticking - with my foot off the gas, it would accelerate to ~60mph on its own. I dropped it into neutral and it reved up to 5000 rpm on its own.

Once I got it home, I expected to find the throttle cable had wrapped itself up so that it was holding the throttle open, but it was fine. I started the car up again and it would rev up to 3500 rpm and just hang there on startup. I unplugged the MAF and idle air controller just to see what would happen and the rpm would drop down to a more normal idle for a moment before rising back up to 3500. If I start it and immediately drop it into gear, it’ll idle normally. If I touch the gas in gear (while stomping on the brakes with the handbrake on) it’ll rev up and not return back down to idle - when I drop it back into park or neutral, it’ll rev up to 5000 rpm (at which point I shut it off so it’s not bouncing off the rev limiter.)

I took the IAC off to check if it was stuck - it’s moving freely, but I cleaned it out anyway. I reinstalled it and still have the same problem - it revs up to 3500rpm and doesn’t settle back down. I checked codes and only got P0326 for the knock sensor, which doesn’t feel like would be root cause of my problem.

Some internet research points to the IAC or temperature sensor, but I don’t have a definitive answer. Has anyone encountered this same problem? Is there anything I should check before blindly replacing the temp sensor and IAC valve? Could any of the recent work have caused this problem?

Thanks for the help! I’m happy to be back in an 850 - it’ll be better when it’s running right!

— ‘VoBro
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