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Date: Sat, 10 Mar 2007 21:00:01 +0000
From: Andrew Sinclair <>
Subject: Re: Wanted: dead throttle assmebly for 99'ish 9-5 or similar

In message <>, Dave Hinz <> writes >My throttle body assembly is going dodgy on my '99 9-5 2.3l LPT engine. >I'd love to get one that's been replaced, so I can dissect it and see >what sorts of things have gone wrong with a failed one. If I'm lucky >maybe I'll see a root cause and a fix-able problem. Anyone replace one >of those beasties (or even a different model but same part) that they >still have laying around the house? Email me please (my address is >valid and unmunged) and let me know what you'd want for it. USA would >probably be best; can't see shipping broken parts through customs. > > Can't help you with a failed throttle body (mine's fine - touch wood!) but the usual cause of problems is the butterfly needing cleaning, gunk and carbon tends to build up around the circumference of the butterfly causing it to stick. Give it a good clean with carburettor cleaner and see if that cures your problems. If cleaning doesn't improve things then the potentiometers could be failing There are a pair, one on the throttle pedal side of the system and the other on the ECU motor driven side, when the resistance's get out of step the ECU complains, trips the TB to limp home and you get a check engine light) this due to the same gunk that coats the butterfly leaking out of seals, I'm not aware if these are easily replaced (or even if you can get them as separate parts), I've not heard of anyone doing anything other than putting a new TB on in this situation. I've lifted this text from a thread on Saabscene that explains how it works. 'When you accelerate/decelerate the potentiometer in the TB varies a voltage to the ECU (related to how much you have put your foot down or lifted it up). The ECU (Trionic) uses this info, along with load requirements, various temperatures, airflow, rpm, etc. to send a signal back to the TB which drives the electric motor round to the desired position. It is the motor that moves the butterfly not the throttle cable in normal operation. The ECU is clever enough to also work out the rate of putting your foot down and can change the mixture ratio when it senses harder acceleration. Related to the rate of change of the potentiometer. The old carburettor equivalent was the diaphragm pump that used to squirt in some neat petrol when hard acceleration was required. It's my own personal belief that a dirty throttle body doesn't respond quickly enough to get the acceleration mixture right and hence some misfire which disappears if you ease off. Seems very sensitive but then this system is supposed to be.' and this also 'On the side of the throttle body there is a black unit with a 10pin connector. The unit has a throttle sensor and a pedal position sensor built in ( Backup )Both of these sensors have to add up to 5v. So,if sensor 1 is 3.1 and sensor 2 is 2.0 a difference of 0.1v is recognised so on comes the "check engine" light and limp home is activated. Causing the revs to drop and more pressure on the gas to pull away.' Cheers, Andy -- Andrew Sinclair

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