I searched the archive and checked the FAQ first, and didn't find anything that matched the problem this car is having.

This 98 V90 is my wife's car, so I don't drive it much. Yesterday, she called me up and told me that the car's motor began to race when she started it. She shut it down, then called me and asked what to do. I wasn't as familiar with the accelerator set up in that car as I am with 700-series, but I figured that if the cable was hung up or binding, all it might need was a blip of the throttle to get the idle to settle down. So that's what I told her to do -- and it worked. When she got home, though, she told me that it still wasn't right, so I had her take my 760 to work today and told her I'd give it a look.

Started the car up this morning and it raced up to about 2500 rpm. I blipped the throttle and it settled down to about 1200 rpm. A little high. The car usually idles around 800 or so. I took my kid to school and noticed that it was still idling a bit high and the rpms fell slower than normal.

After I got back, I let the car cool off for a couple hours and took a look. Same symptom as before when I started it. I removed the cover from the pulley system and rotated them, then letting the pulley snap back, checking the cable for free movement. Everything looked fine. Started it again, and this time the engine speed raced up to about 3500 rpm. Hadn't touched the accelerator pedal.

I pushed on the rod that connects the pulley system to the throttle body, and this caused the speed to drop. I pushed harder on the rod and got the idle speed to drop to a normal (~800rpm) level.

Interesting. I played around with it a bit more, and determined that if I just blipped the throttle by rotating the pulley, unpredictable things happened. Most often, it would return to a somewhat high idle, occasionally it would return to a very high idle. But in all cases, if I pushed the linkage rod firmly down, I got the idle to drop back down to ~800 rpm.

So, this sure sounds like a dirty throttle body, doesn't it?

It got me to wondering, though. The onset of symptoms was sudden, not gradual. I would have thought that a dirty TB would gradually show signs of worsening performance, not suddenly. Perhaps it finally got gunked up such that a critical line was crossed?

My next question is specific to cleaning the TB: I've cleaned 700 TBs before -- pretty simple, really. Never cleaned the V90's, though. Never had it off, either. I checked the FAQ and could find no info specific to the B6304 engine's TB. Just wondering if there's anything I should watch out for when cleaning the TB? I read the comments about using fuel-injection system cleaner only with interest. Didn't realize that regular old carb cleaner could mess things up. Good to know.

Thanks for any advice you can offer here.

Best,

Michael