Date:         Fri, 24 Nov 95 18:32:08 0800
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Steve Hoge <steveh@emu.com>
Subject:      Throttle Switch Thrombosis

Isn't fuel injection FUN?

OK, the latest on my Digifant-equipped '89 Syncro is that I'm getting 
an incredible surge/lag effect as I accelerate/decelerate. Touching 
the gas causes it to accelerate (smoothly, and with good power), and 
letting my foot off causes it to instantly and dramatically 
decelerate.  When cruising at speed on the freeway, where the car 
should be subtely balanced between the two, say around 3000rpm, it 
can get into a violent oscillation and shuddering effect - very 
scary. 

I don't think it's related to the bad gas I got a couple of weeks ago 
(see the Techron posts), but it *did* start to happen pretty soon 
(but not immediately...) after I cleaned the Panamint dust out of my 
engine compartment with the hose (I took the precaution, suggested 
by a correspondent, of unplugging the distributor and covering it 
with a plastic bag, but otherwise pretty much sprayed all around.) 

According to my reading of Bentley, this surge/lag is the same affect 
that I should see if the throttle switch gap is too big (ie, > 
.01mm). However, I can't see how moisture in the engine compartment 
could have affected this clearance. Unplugging, cleaning and 
reseating the connector between the throttle valve switch and the ECU 
(done at midnight under a streetlamp...) *seemed* to help for awhile, 
but the effect eventually returned.

Is it possible that I've toasted my throttle valve switch?  Water in 
there somewhere making intermittent contact?  How expensive are these 
parts?  Of course, Bentley makes disassembly look easy but in reality 
it's wedged beneath manifolds, my (non-functioning) cruise control 
stuff, etc.:-P  Also, I believe I'd have to do a idle recalibration 
after reassembly, no?

A larger question: is there any "Idiot's Guide to Bosch Fuel 
Injection  Systems" out there that I could read to get better theory 
of operation on my FI system?  I've perused our FAQs and there're 
lots of good details on FI but I didn't exactly come up with a global 
overview of the system.  Anything short of enrolling in a German 
technical institute to get a better understanding of this stuff?

Steve Hoge
'77 AutoLoaf  (Da Rust Bucket)
'89 Syncro GL (Da Shudder Bucket)