Engine Surging?

[54406]

My recently purchased '99 SC400 with 51k is doing something a little like the surging the recent BMW motorcycles were doing.

When I am maneuvering at a slow speed, slowing down to stop for instance, the engine seems to give a little surge which feels like the brakes failing, which you reflexly counter by pressing down harder on the brakes, then you are over braking , etc. I have also noticed that when running along at highway speeds if you take your foot off the gas quickly the tach needle bounces up about 200-300 revs before it starts to drop down.

Anybody seen this before? Whass hoppnin?

[92blackSC400]

Is this happening with the A/C on? If so, repeat with A/C off.

I had a similar condition with my 156k, but the idle was about 1100 when braking with the A/C on. I cleaned the throttle body assembly and the problem went away.

[sightdev]

you are probably feeling the downshift. its more noticible compare to the other cars. Throttle cleaning may help the uneven idleing. It has two throttle opener compare to one on most cars. I stuck a long screw driver inside with rag under the screw driver to catch the dirt (carbon). Jeep forum folks also recommended Valvoline throttle cleaner which IMHO works the best compare to host of other brands that i have tried in the past 23 year of driving. SC400 is not so easy to work with (except for air filter change) because you have to move something to do anything. Toyota is famous for carbon deposits because of rich mixture at higher RPM to boost performance. Toyota was fined several hundred million dollars 1-2 years ago, and Toyota also have many hushy hushy repairs because of federal ruling (i guess all have hushy hushy repairs). Clean out your fuel system and change oil regulary and the engine will run forever.