Date:         Wed, 6 Oct 2004 14:50:35 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Rough Running 1.9L
Comments: To: Paul Connelly <paul@THEMOUNTAINSUSA.COM>
In-Reply-To:  <000e01c4abcd$0365dff0$026fa8c0@PAUL>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 13:50 10/6/2004, Paul Connelly wrote:
>Help! We have a stranded couple with a 1.9L '85 westy who stopped by my
>shop after seeing my '86 outside. I know little enough about the 2.1, but
>have never looked at a 1.9. The symptoms are: Sounds like its running on 3
>cylinders. Exhaust is sooty and does smell of gas. Plugs look like it has
>been running a bit rich. Cap, rotor and leads seem okay. The first
>"switch" on the throttle (from idle) doesn't seem to work, but the full
>throttle is okay. The symptoms they felt when driving (Up Vail Pass from
>about 7,000' to 11,000') under load seemed to pull fine. From 11,000' down to

Idle switch fail open shouldn't be a big deal; fail closed would cause
severe driveability problems but you don't have that.  Squirt some CRC
Electronic contact cleaner where the actuating pin enters the switch and
operate the switch repeatedly may well cure it, assuming it isn't just
adjustment.  Adjustment is set adjusting screw so that switch *barely*
closes as you ease throttle closed, then add one full turn.


While problem is happening, measure O2 sensor voltage and also measure
voltage across T II sender (two-terminal sender at thermostat housing
left-rear of engine.  T-II should show under a tenth of a volt on warm
engine.  Use a needle through insulation of the wire on the non-ground
side, to the ground bolt at left head. If high, sender is bad or bad
contact or bad ground.  If close to zero, turn off ignition, unplug the
sender, ignition on again and look for five volts on that line.  If still
zero, broken wire to ECU or ECU problem.

Unhook O2 sender and leave unhooked -- it's either causing the problem or
confusing the diagnosis.  Check the lead going to the ECU after unhooking
the sender, should be a constant half-volt.  If it's shorted to ground ECU
will drive everything full rich as soon as the T-II sender signals
warmup.  ECU can get confused after any intermittent signals, it starts
fresh if you power off for a half second.

Put a voltmeter or scope on AFM leads, ignition on and watch the voltage as
you move the vane (*very* slowly if using a meter) -- should have constant
rise/fall with no dropouts.  If it's noisy with dropouts, will confuse
ECU.  "Capacitor cure" can be helpful here, 22uF 16-v or better tantalum
cap connected from AFM wiper to ground terminal.  I doubt you'd get this
super-rich condition from that, though.

Check injectors for stuck open...I suspect a stethoscope would be very
helpful but the final check of course is pull them and look.  Check fuel
pressure regulator vacuum connection for signs of raw fuel leak into manifold.

david


--
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage," '85 GL "Poor Relation"