Date: Sat, 18 Aug 2007 22:05:41 -0700
Reply-To: Scott Daniel - Shazam <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Shazam <scottdaniel@TURBOVANS.COM>
Subject: Re: A bit rough idle, running. Unbalanced injectors?
In-Reply-To: <e3e1d7f0708182050yf0e9b4ds768255c11714e08f@mail.gmail.com>
Content-Type: text/plain; charset="us-ascii"
The engine coolant temp sensor has been ohm checked for resistance relative
to coolant temp ?
List all your symptoms.
What I get is :
Rough idle, ( is it warm, or cold, or both ? )
Poor fuel economy.
Cylinders running at different mixtures is highly unlikely.
A worn injector or two with a poor spray pattern is somewhat likely, but of
hundreds of VW injectors that pass through my shop, I replace about one
every 5 years., or barely ever.
You could try a high quality fuel additive for cleaning injectors - Lucas
brothers is a real good one.
If the injectors came out easily, like on a vanagon, you could observe the
spray pattern, but not easy on an EV I believe.
You especially could read the spark plugs to determine mixture in each
cylinder.
If you found one richer or leaner you could move the injectors around to see
if the symptom follows the injector - that way you'd be sure it was a faulty
injector or two, or whatever.
I don't believe you have considered intake manifold leaks as a source of
rough idle.
Does it run normally and strongly throughout the rpm band ? or not ?
Scott
www.turbovans.com
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Martin Jagersand
Sent: Saturday, August 18, 2007 8:50 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: A bit rough idle, running. Unbalanced injectors?
Still no resolve to the (slightly) rough running I5 engine problem
in my '94 Eurovan (T4) Westy. Somehow I'm thinking it's related
to cylinder power being unbalanced. I checked ignition. Appears ok on all
5 cylinders. As you remember, I had checked compression already.
I wanted to check O2 sensor, and found the sensor under the van,
but couldn't find where the wire went up in the engine compartment.
(to unplug and measure)
Most aspects of the digifant seems to work as expected. (ie it
reacts as expected to temp sensors, goes through high idle to
low idle at startup etc..
I'm still suspecting unbalanced injectors could be part of the problem.
Hypothesis: Vibration/rough running is due to unequal power from cylinders.
Bad fuel economy from some cyls running rich some lean.
Occasional warm start difficulties from some cyl being too rich/flooded.
(Always starts if I wait a while (up to an hour). Presumably fuel has time
to evaporate)
Do these thoughts make sense?
It was unclear to me how to pull the injectors. There seems to be some
kind of plastic assembly inside the intake manifold bend. Is that the
injectors? (Unfortunately the T4 engine compartment is a lot more cramped
and harder to get an overview of than the T3 vanagon).
Anyone knows the procedure?
Also both the VW dealer and an independent shop failed to find what's wrong.
Any more ideas?
Thanks,
Martin
On 7/8/07, Matt Roberds <mattroberds@cox.net> wrote:
>
> > 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.
This one has been rough since I got it used at 100tkm, but fuel economy
has worsened over the years.
> 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.
Didn't find any problems here.
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.
It's not having a problem maintaining idle. RPM is steady at both high
(1000rpm)
and low(800rpm) idle. It is just that the engine runs rough/vibrates way
more
than other I5 T4's.
> 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
>
>
--
Martin Jagersand
University of Alberta
http://www.cs.ualberta.ca/~jag/
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