Date: Mon, 24 Jan 2011 14:52:59 -0800
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: 85 Vangon revs drops, revs drops, revs drops,
and then dies after a few minutes of this cycle
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reply-type=response
my thoughts..
I've never seen a throttle switch stick closed ..
the opposite is common of course.
there are two kinds of 1.9 throttle bodies, the early ones with the switches
right on top..
and the later ones ....which have a 2.1 style switch on the bottom..
fairly rare throttle body ...used 2nd half of 85 is my guess.
if contact is not made at idle..
it can 'run right' but it won't idle right.
if the throttle switch stays closed with too much open throttle ..
say you want it closed at zero throttle but breaks contact at 5 % throttle
..
if it goes to say 10 % throttle before not making contact..
you get bucking at very low throttle openings.
You want it to make contact as close to zero throttle as you can ..AND
...every last time the throttle closes ....it must make contact.
if you try to get it to make contact really really close to zero throttle
..it may not return to 'real zero throttle' every time ..due to sticky
throttle cable, no slack in it, ...sticking/binding throttle plate etc.
so as close as you can get it, and make sure *everytime* it makes contact at
zero throttle.
here's what I find ..
they will work and run with all sorts of things out of whack..
throttle switch , timing too advanced, air intake leaks, weak AFM, dead
oxygen sensor, poor Temp sensor II etc.
but ......if you want it to do what it's suppossed to do ,which is...
start instantly,
idle consistently,
go right,
not stall when coming to a stop,
proper emissions and decent fuel economy and power ..
it ALL has to be right.
typical deal...got one 1.9 wbxr here ....pulled to do a TD engine
conversion. - the second I heard it I could tell it had about 20 degrees
advance at idle on the timing.
I can also get very close on what the compression is of any engine ...just
being near it. ..but you have to sort out what is improper running, and what
is weak compression.
to give one example of how it's 'more than just idle quality' about throttle
swithch ..
this was an auto trans 2.1
the problem/symptom was it would just start idling very fast ...like a bad
Idle Air Valve or contorl unit.
but I didn't start there.
I was checking things like timing while it was idling ..
then it just took off to 2,000 )+ rpm .....
so I shut it off.
then it wouldn't restart.
hmmm...
I had already checked the Temp Sensor II ..
then realized what was going on ..
besdies the throttle switch not making contact ( and I had to remove the
throttle body to get that working and moving again ..some are just rusted
and stuck 'forever' ) ..and besides timing being a bit fast...
I realized the temp sesnsor was likely OK cold, but wonky hot.
put a new one of those in.
removed t-body to get the switch adjusted right ..
adjusted timing and idle rpm ..
end of problem.
point is ...if the ecu does not see 'idle switch contact' ..........it can
'get confused' let's say.
the temp sensor ...
they come in two grades....cheap made in you know where and original german
..
I always recommend not using parts from you know where ...at least most of
the time.
but 'it all adds up.'
another one I fixed ..after the guy spent 600 on a new distributor twice in
a year...
and he doubted me but by golly ..
just attenting to throttle switch, timing, and an exhaust leak near the
oxygen sensor ..
that van worked perfectly after that. Total parts- on or two exhaust port
gaskets.
It's not mainly in the parts ..it's in the cleaning, inspecting, and
adjusting.
People and shops throw parts at problems when they don't understand the
systems or have good ( often very simple ) ways to test things. A timing
light has about 10 uses, not just for checking igntion timing.
You know ..
an infra red temp gun can find a misfiring spark plug in 5 seconds,
non-intrusively. Use imaginantion.
scott
www.turbovans.com
----- Original Message -----
From: "David Beierl" <dbeierl@ATTGLOBAL.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Monday, January 24, 2011 2:06 PM
Subject: Re: 85 Vangon revs drops, revs drops, revs drops, and then dies
after a few minutes of this cycle
> At 04:30 PM 1/24/2011, John Rodgers wrote:
>>with this - insist that the difficulty is the throttle switch. The
>>settings for the thing is critical and wear and whatever can really foul
>>things up. This is a sorely neglected maintenance point. Nobody checks
>>it - they just drive until the engine sputters and quits - then they
>>"holler for the calf rope!"
>
> If the closed-throttle switch on a 1.9l doesn't open when it's
> supposed to you'll think you're in a giant slow paint shaker when you
> accelerate from idle. I don't think failure to close will actually
> make that much noticeable difference (what should happen is that the
> engine will shut down until you get below x rpm, but you won't notice
> it not doing that unless you're monitoring the injectors). Neither
> failure to close nor failure to open will stop it idling.
>
> On a 2.1l if the switch doesn't close the engine won't idle down
> properly, it will sit above 1000 rpm and hunt. Not certain what will
> happen if it doesn't open - on the 2.1l the decel shutdown doesn't go
> into effect until the engine has been above 2500 rpm and by that
> speed with the throttle open I'm not sure what the ECU would make of
> the situation.
>
> The reason so many are found to be not working properly is that the
> usual failure condition, failure to close, doesn't cause dramatic
> symptoms. It's not a progressive failure, at any given moment it's
> either working or it's not.
>
> Yours,
> David
