Date: Sat, 9 Oct 2010 18:32:46 -0700
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: It continues - Engine RPM Hunting 200-500 rpm
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hi john,
first, with engine off, open the throttle with your hand.....you should hear
a click.
If you do not, the throttle switch is not making contact.
it can be adjusted in place with the right Allen wrench ....but it's tricky
sometimes.
Removing it to work on adjusting the idle switch isn't hard.
You want it so that closed contact is just barely off of the 'parked'
position of the throttle.
So you just barely open it...you hear the click.
it's not a bad idea to use an ohm meter to confirm that it's actually making
electrical contact.
the most important thing is that every time idle returns to zero , it makes
contact.
.....that's hyper important ..you don't have that, you got nuthin' for good
idle.
if you don't have that ..you'll never get anywhere on steady decent idle.
before I forget btw .....
well, first , I find the throttle switch not making contact on what seems
like 95 % of all vanagons I work on for running/tune issues. In other
words...'almost always.'
I also just found one with a temp sensor II that was OK cold, but warm , it
was open, no resistance reading, I checked it twenty times .. new one fixed
that nicely.
if by idle stabilizer you mean that Idle Valve .....silver can on top of the
engine ..
just leave that connected.
I only encounter two problems with that system ...
it doesn't work and cold idle is not faster than normal.
or ...rarely ....it can mess up and cause very high idle when it shouldn't .
If that happens disconnect, but otherwise leave it connected. Disconnecting
it for troubleshooting purposes is fine and smart. ..
just in case it's making the idle weird. or uneven.
can say enough ..
intake leaks, intake leaks....can't have any, anywhere. Spray around with
carb cleaner ( engine running ) looking for idle to change or be affected
when you spray on a spot. I have found up to 8 intake leaks on one engine
before...check the entire intake system ..from throttle body to cylinder
heads.
timing ..I find too advanced timing 'all the time' ....like 'most' vans have
too advanced timing it seems.
It can't idle right if timing is too advanced.
5 degrees too advanced is ok ....but not more than that. Of course it can't
be retarded either.
Disconnecting 02 sensor as a test is fine.
I like to always read their output with a volt meter.
I also adjust the mixture screw on the air flow meter sometimes.
It's find to adjust idle speed with that large screw on the throttle body ..
that's a pretty non-technical adjustment ...you can't get in a lot of
trouble trying it at different positions. Idle speed should change
significantly turning that screw ..if it doesn't , something is not right
...either air leaks, or the throttle body itself.
even with 5 things out of whack, it should start and run easily cold.
No dancing on the gas pedal should be needed to keep it from stalling.
the only injectors I trust are the ones I see spray nicely myself.
I have gone through 15 used injectors before to find 4 that spray really
nicely.
Fuel filter clogged ?
if it won't idle cold without dancing on the pedal or using some 'pedal
technique' ...a few things should be out of whack enough that they shouldn't
be too hard to find.
I'd sure look at a spark plug or two .
this one I just fixed...
the one with the open temp sensor II when hot ...
and no idle switch contact ....it was find cold.
'Cold' is a very strong running mode..
usually they start and work well cold .
I would be looking for wet spark plugs ..
I almost never replace them ( though I did on this last van ) ..they really
last well and are not a weak link ...but reading them can sometimes tell you
something.
and you should check compression too.
and make sure you don't have a failing or clogged cat or muffler.
I find that now and then too.
I have seen a few vans with the 02 sensor wire to the ecu replaced ...
they chopped off the original one near the ecu , and spliced in a new one.
a shorted 02 sensor wire could cause all sorts of weirdness.
you should ohm check your temp sensor II also ...cold and warm.
always start with the basics.
Scott
www.turbovans.com
----- Original Message -----
From: "John Rodgers" <inua@CHARTER.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Saturday, October 09, 2010 3:56 PM
Subject: It continues - Engine RPM Hunting 200-500 rpm
> I have been tinkering with my 91 Carat and have still not resolved the
> hunting issue.
>
> On cold start-up I have to play with the pedal to keep it running - up
> and down between 1000 and 2000 rpm. As it warms up, it begins to settle
> down. Not as much footwork to keep it running. Eventually it will idle
> smoothly around 1000 rpm. But if I try and accelerate the engine above
> the 1000 rpm range - it goes into the hunt mode again. Around 2000 rpm
> it will run relatively smoothly.
>
> The injectors have been serviced and run in another of my vans, so I
> know they are good. All the hoses are good, and I carefully inspected
> the vacuum lines just to be sure. The crankcase vent host is new.
>
> I disconnected the idle stabilizer valve after warm up, and restarted.
> It was a little rough to start, but after start-up it smoothed out at
> 1000 rpm like before, and still would not run properly between 1000 and
> 2000 rpm.
>
> I have not disconnected the O2 Sensor yet. O2 sensors have caused rough
> running on my other vans, and smoothed out when disconnected, but this
> is a little different.
>
> So apparently, this takes me to the throttle switch - I think. But this
> engine has only 114,000 miles and is clean, so I'm suspicious about
> whether it's the switch or not. Never tampered with the switch before,
> so a little unsettled about working on that.
>
> Any input on this would be appreciated.
>
> Thanks,
>
> John
>
> --
> John Rodgers
> Clayartist and Moldmaker
> 88'GL VW Bus Driver
> Chelsea, AL
> Http://www.moldhaus.com
