1999-2009 [Subscribe to Daily Digest] |
 | [Main 95 Bulletin Board | BBFAQ |
Prev by Date | Next by Date | Post Followup ]
Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
Three things typically go wrong with TBs Posted by Gary Stottler [Email]  (#1463) [Profile/Gallery]
(more from Gary Stottler) on Tue, 15 Dec 2015 06:23:23
In Reply to: Do bad throttle bodies always throw codes?, steve, Mon, 14 Dec 2015 10:07:31 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Three things usually go wrong with a TB:
- An electrical circuit fault (open or shorted) in one of the potentiometer traces or a "rationality fault" between the two potentiometers (meaning that they don't agree with each other). These problems will always result in Check Engine Light and code set and most likely the system going into limp-home mode. Can't be fixed by cleaning. I question the statement that was made about a software change to make it less likely to set a code. Is there documentation that someone has about that? It is possible that codes were being set due to system voltage variation in older cars, for example, where the TB was perfectly good, but it's doubtful that there's any way to "cover up" a bad circuit so no code set if the circuit is really bad. Typically it's good, open, or shorted - hard for the electrons to get "weak".
- Dirt builds up on the throttle blade and throat causing the airflow to be reduced at idle. This can cause rough idle, sags, and stalls and can be fixed by cleaning as long as no one has dicked with the base throttle blade position. In that case, all bets are off and it's hard to get it to work right again.
- Air leaking into the throttle body due to wear in the shaft/bushings. This can cause both idle problems and surging because it screws up the interaction between the air measured by the MAF (which only works under certain conditions) and the air calculated by speed density (engine speed, manifold pressure, throttle position) which is actually what's used most of the time. This can't be fixed by cleaning, only by replacing the worn part.
If your TB is clean and tight and you have no CEL then your problem is likely elsewhere in the system. Look for vacuum leaks, dirty injectors, low compression, etc., etc.
Hope that helps!
Best,
Gary
_______________________________________ Gary Stottler
, Tue, 15 Dec 2015 10:47:39, Tue, 15 Dec 2015 06:23:23 <-- Viewing This Message
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
 |
 |
 |
 |
 |
