My 1997 Vanden Plas X300 is having a bit of trouble with a sticky throttle. At freeway speeds, the car will want to stay at around 3500 rpm even after I let off the accelerator. I find that I am braking all the time. Usually, a quick toe-tap to the accelerator will release the throttle and she'll resume a normal idle speed.

I suspect the throttle butterfly valve is sticking open due to gunk build up over time.

I have read different opinions here (and elsewhere) on the best approach to cleaning the throttle body:
(1) Remove the TB completely to clean vs cleaning without removal;
(2) Using throttle body cleaner vs other types of cleaners;
(3) Using fuel additives
etc

Any help would be appreciated.

Thanks,

Dave[sm=violin.gif]

 

cleaning them is only temperary.. cleaning them in depth usually distroys the butterfly bearings.. only fix is a new one..

 

FOLLOW UP (for those interested):

I took the housing/rubber boot off and thoroughly cleaned inside it. There was quite a bit of carbon build up on everything. (Not too surprising after 110,000 miles, I suppose).

Without using any chemicals, I cleaned the inside of the throttle body by using small pieces of cloth wrapped around my finger. Then I employed the same process - delicately - on the butterfly valve (both sides). Basically, I did this over and over until no more carbon/soot came off onto the cloth pieces.

Lastly, I took off the small hose (which comes from the top of the engine to the throttle body) and cleaned the inside of it by pushing small pieces of cloth through the hose using a sturdy piece of bamboo. Probably 4-5 times before all the carbon was gone and the cloth came through clean.

Put it all back together and voila!!! Problem solved. No more fast idle after decelerating!!!

But the icing on the cake is a marked improvement in horsepower. I think the poor thing was starved for air - or maybe just clean air.......

I assumed the sluggish performance was merely age-related, but she feels young again. When I accelerate, she jumps!

Has anyone seen a big improvement in HP after a good TB cleaning? This really is an amazing difference.

 

It makes all the difference in the world. You're not alone in noting the improved performance and smooth operation. Check you gas mileage as well. I'll bet that improved as well!

 

Although I have limited experience with the particularpart having only one X300, I have cleaned it a few times. There is no problem I can seeif the part is removed and cleaned carefully. The thing to avoid is getting dirty solvent draininginto the TPS, removing the part will solve this, even with the throttle body on the car. I always put atiny amountof turbine (non-detergent)oil on the shaft at each bearingafter cleaning, but I'm not sure how critical this is. To suggest that owners replace the throttle body each time it needs cleaning is pretty severe.
Brian C.