Shudders at stop light: Clean throttle body?
 

98 Saturn SL 114K miles

When I stop at a light, within about 30 seconds, sometimes sooner, sometimes
longer, the car will shudder like it is going to stall and the rpms drop
from the normal 800 (idle) to about 700. It bounces right back and doesn't
happen again. Sometimes when it bounces back I hear a low pitch, muffled
brrrmmm sound, for about a second.

I have searched through news groups and most of the suggestions for a
similar problem is either a vacuum leak or the throttle body needs cleaning.
But most of what I found talked about it happening more often. Not just at a
stop sign. Is there a way to confirm this? There has been no SES/MIL light.

About a year ago I had the fuel pressure regulator replaced, in the past
month or so I've gotten a new air filter, EGR valve, and crankshaft position
center. I just ran a bottle of Gumout injector cleaner through the tank, the
one for high milage engines.

Are there any warnings about cleaning the TB? I've read things that just say
spray cleaner in it and scrub it hard. Some warn to only use a soft brush,
and others warn not to let the disolved carbon get into the engine.
Chilton's says not to get solvent on the IAC or TPS, but Hayne's gives no
such warning. Can I clean it in place, or should I remove it and pull the
sensors from it, too?

Richard

On Thu, 16 Dec 2004 19:09:27 GMT, "Richard" > wrote:

>98 Saturn SL 114K miles
>
>When I stop at a light, within about 30 seconds, sometimes sooner, sometimes
>longer, the car will shudder like it is going to stall and the rpms drop
>from the normal 800 (idle) to about 700. It bounces right back and doesn't
>happen again. Sometimes when it bounces back I hear a low pitch, muffled
>brrrmmm sound, for about a second.
>
>I have searched through news groups and most of the suggestions for a
>similar problem is either a vacuum leak or the throttle body needs cleaning.
>But most of what I found talked about it happening more often. Not just at a
>stop sign. Is there a way to confirm this? There has been no SES/MIL light.
>
>About a year ago I had the fuel pressure regulator replaced, in the past
>month or so I've gotten a new air filter, EGR valve, and crankshaft position
>center. I just ran a bottle of Gumout injector cleaner through the tank, the
>one for high milage engines.
>
>Are there any warnings about cleaning the TB? I've read things that just say

If you are going to clean it in place, use the brush to break the hold
the carbon has on the body and get good shop towels to wipe it out
clean. Just working on the valve and where it seats did wonder for
it's 'unsticking' for me.

Now the warning, don't fret about goind 'deep' you could drop
something and I highly recommend you drive secure the tooth brush via
a strong string so if you do drop it, it's retrievable.

hth,

tom @ www.ChopURL.com




>spray cleaner in it and scrub it hard. Some warn to only use a soft brush,
>and others warn not to let the disolved carbon get into the engine.
>Chilton's says not to get solvent on the IAC or TPS, but Hayne's gives no
>such warning. Can I clean it in place, or should I remove it and pull the
>sensors from it, too?
>
>Richard
>

Hi I just bought a 97 SC1 from my sister who had a trouble with the car
stalling and or not starting. It sat unused in her driveway for the
past year or two. It has 65,000 miles on it. She had it service many
times. They replaced the module and several other things. Any advice?
Mary