Date:         Sun, 22 Apr 2007 19:17:17 -0700
Reply-To:     John Bange <jbange@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         John Bange <jbange@GMAIL.COM>
Subject:      Re: Vexing Subtle Misfire Issues
In-Reply-To:  <001401c78541$274043c0$0201a8c0@kaos>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

>
> You did not mention if you took care of the engine grounds.There are
> several
> that are critical.


Yeah, grounds are DEFINITELY good. One of the weird obsessive things I did
when I put in the new engine was run a  #6 stranded copper "ground bus" all
around the vehicle, bonded to the body at all the important ground points,
and 16ga auxiliary "feeder" grounds to EVERY engine component that may or
may not use a ground return. It's grounded like crazy

How about disconnecting the ECU from the O2 sensor but leave the meter
> hooked up to the O2 sensor. Drive around a bit to see if it is running
> rich
> or lean. An adjustment to the AFM  spring could correct it.


Runs appropriately rich in open loop, but still has the misfire problem.

Was the spare AFM new? If not they both could have a fatigued spring.


Not new, but mixture is adjusted according to the Bentley with an Innovate
LM-1 wideband O2 sensor.

Do the spark plugs have the correct heat range?


Yup. Bosch W7CC0's.

I have found an Inductive Timing Light  to be a useful tool in situations
> like this. Harbor Freight has them dirt cheap. Perhaps you could clamp it
> to
> each wire, one at a time, and narrow it down to one cylinder.


Hmmm... good idea. I'll steal my timing light back from my brother and try
it. I think I may have tried that once when the problem first appeared a
year ago, but now I don't remember! Cheaper than a new fuel injector, that's
for sure.

--
John Bange
'90 Vanagon - "Geldsauger"