850 driving by itself

robrichie · Post by **robrichie** » 27 Oct 2004, 13:10

I have a 96 850 turbo. When I am driving it, the car at frequent times just sort of takes over and maintains it's speed, just like cruise control was on but it is not. It does this at all speeds. Sometimes when I am idiling at a light, the engine will rev up to around 3000 rpm and I have to keep tightly onthe brake to keep the car from lunging forward. It will rev up for a few seconds, then back itself down to a normal rev. My check engine light is on of course. Bad MAF sensor? Other suggestions please? Many thanks.

Post by **matthew1** » 27 Oct 2004, 14:05

Air filter clogged; throttle body dirty; vaccum hose not attached; idle control broken.

jrandle · Post by **jrandle** » 02 Nov 2004, 10:38

My 850 R was doing the same thing. I had the throttle body cleaned and it didn't help. I checked the vacuum hoses and they were fine. My check engine light was on as well. I replaced the coolant temperature sensor and it is normal ever since. Let me know if that works for you.

Cossack · Post by **Cossack** » 08 Nov 2004, 18:23

See if this post describes something similar.

https://www.matthewsvolvosite.com/chat/p ... =o2+sensor

I had something similar going on, progressively got worse to the point that the car was almost impossible to drive.

I replace the front O2 sensor, and it did the trick. Relatively easy and cheap if you do it yourself.

Good luck

Cossack