Date: Sun, 8 Jul 2007 22:11:21 -0500
Reply-To: Matt Roberds <mattroberds@COX.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Matt Roberds <mattroberds@COX.NET>
Subject: Re: A bit rough idle, running. Unbalanced injectors?
In-Reply-To: <20070708163754.WUEU17477.fed1rmmtai111.cox.net@fed1rmimpi03.cox.net>
Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
> From: Martin Jagersand <jag@CS.UALBERTA.CA>
> Date: Sun, 8 Jul 2007 10:00:37 -0600
>
> I have a question about a gas engines rough idling and running.
> This is my '94 Westy, so its the I5, but I imagine the 4cyl can
> have similar symptoms/problems also.
>
> Symptoms are:
> Rough running. Not misfiring, but just rough.
> Particularly noticeable as a vibration at idle (but motor mount ok),
> but also noticeable at speed and as a rough sound when accelerating.
Did it used to feel better, or has it always been this way? A
five-cylinder engine will never be as smooth as a six.
> Having worked only on Diesels my whole life, gas engine electronic
> injections and the many ways they can give trouble is beyond me, so
> I'm hoping for some advice.
You might do the simple stuff first, like a tune-up. Air filter, fuel
filter, plugs, wires, distributor cap (if so equipped), rotor (if so
equipped). Check the ignition timing. Consider replacing the O2 sensor,
especially if the van has >80,000 miles or if you don't know when it
was last changed. If that's all OK...
Check the stuff that is common to all the cylinders first. In
particular, look for air leaks between whatever air measuring device it
has (flap box, mass airflow sensor, etc) and the cylinders: check all
rubber boots on the intake, make sure gaskets are there and intact,
clamps are tight, etc. Check all vacuum hoses, especially any hard
nylon ones - these love to get brittle and break at the slightest
provocation. Leaks will let in "extra" air that the fuel injection
computer doesn't know about and will cause poor running.
Check the throttle body. Look for gunk on the walls around the throttle
plate and on the throttle plate itself - if there is some, clean it out,
using maybe carb cleaner and rags or a brush.
Check whatever idle control mechanism it has. Some fuel injection
systems use a valve to bypass air around the throttle plate for idle,
and the working end of this valve can get gunked up. Take the valve off
the car and clean it out - again, carb cleaner, rags, a brush.
> Could it be just unbalanced injectors?
I am not a professional mechanic, but in over a decade of fooling around
with cars on a hobby basis, bad injectors seem to be pretty far down on
the list of things that can make a fuel-injected gasoline engine run
rough.
Matt Roberds
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