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"You were supposed to destroy the sith, not become one" - Obi Wan Kenobi.
"You were supposed to be the failure fallback, not cause the failure!" - Obi Wan Calvoni
It's TCS, this immediately heralds replies of "just swap it out". If you have that response, please don't both responding. It'll be swapped out at some point.
Basically, I've been chasing issues on my 9000 after getting it back on the road. My throttle is just... awful. Its kinda clunky, feels like it's dragging halfway through, etc. Not boosting great, idle issues. And I had a latent check engine that was "5" flashes, AKA throttle position sensor. I had the sensor replaced last year or so by Jeff @ EMS.
So, I spent that afternoon running through the traction control diagnosis manual:
https://drop.ceux.org/saab/tractioncontrolsystem.pdf
I checked the pedal pot and some other electrical checks, and it all checked out within spec.
So then I sort of gave up and was mucking about in the engine bay, and I thought I'd check the vacuum lines. my red/white check valve was kinda leaky so I went to swap it out. Then upon testing it - I was recieving an unlimited supply of fresh air.
What does the red/white check valve, and the air control valve on the firewall do? the TCS system, upon finding a fault or something, can go into limp home mode. It "grounds" the air line. It opens up so there's no vacuum applied to the hose that runs into the ETB. This causes the diaphram to drop down. and engage the backup physical throttle body. This attaches to the throttle wire that connects in from the pedal all the way up to the TB.
If open it up and you look at it - you'll see it's just a regular throttle body under there - with vacuum diaphram driven "switch" that engages and dis-engages it.
On normal operation, the vacuum runs off the manifold, to the check valve (to prevent boost entering the ETB diaphram) , the TCS control valve is closed by the TCS ECU, and the diaphram is sucked in, moving it up and out of the way (see the pictures).
So back to the diagnosis. I am having a major leak here, and it's weird because, it's coming from the throttle body! Up to this point I didn't really know what was under there.
So I took the TB off. For reference, it's 3 13mm nuts, the two water lines, the ETS electrical connector, and a vacuum line. That's all.
Put it on the bench and opened it up and.... diaphram is shot. crap.
So what was happening? The ETS system was engaging as normal, and then fighting (you can hear it whine) the fallback system as they were both trying to operate at the same time.
My premonition is that two things in general could cause this. - you put the check valve in wrong, boosted and blew the diaphragm - or the diaphragm fails from old age.
So... I did something somewhat dumb and for now just removed the entire fallback mechanism. The car now drives like a bat out of hell - but maybe more like a cat with just one life left.
That's all folks - the quickest way to test is to apply vacuum on the line leading into the throttle body diaphram on the top of the ETB and see if it holds, if not your diaphragm is shot to shit.
Here's two photos for posterity.
https://drop.ceux.org/saab/9000_Misc/diaphragm.jpg
https://drop.ceux.org/saab/9000_Misc/no-fallback.jpg
posted by 131.106.22...
, Mon, 20 Feb 2023 09:14:30
11
, Thu, 2 Mar 2023 22:04:30
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