Date: Mon, 11 Oct 2010 00:23:40 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: It continues - Engine RPM Hunting 200-500 rpm
In-Reply-To: <4CB0F30C.8060007@charter.net>
Content-Type: text/plain; charset="us-ascii"
Since you have a poor running problem, the bad idle is just a symptom, not
the cause or a problem by itself.
Poor starting/cold performance issues can be caused by a number of problems.
The O2 sensor is out of the picture when first starting or on a cold engine.
Engine condition. Bad intake valves are worse than vacuum leaks.
Compression/leak down!
For vacuum leaks inspect the manifolds if any signs of rust. They can leak
where attached to the end castings.
Temp 2 sensor. The sensors rarely go bad but the plug connection is a
frequent problem. So is the ground connection for it.
Ignition, make sure all four cylinders are firing. The wire ends at the
plugs can short to ground or the resistors can open. Common on aftermarket
wires.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
John Rodgers
Sent: Saturday, October 09, 2010 6:56 PM
To: vanagon@GERRY.VANAGON.COM
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