Date: Thu, 7 Oct 1999 09:57:26 -0400
Reply-To: Bulley <gmbulley@BULLEY-HEWLETT.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Bulley <gmbulley@BULLEY-HEWLETT.COM>
Subject: Re: Intermittent Ignition miss, no start,or rich running,
need help!,LONG
Ezra-
The problem is not some complicated, obscure capacitive-resitance
field-induction modulation reticulator fitting. It sounds like the gaps on
the plugs might be a bit too wide. I know they are new, but did you gap
them to your engine's specs? Also, when was the last time you ran a bottle
of Techron(r) through the Fuel system? The symptoms you describe sound like
crapped up injectors, or plugs that are the wrong brand, heat range, or
gap.
Good luck, let us know.
G. Matthew Bulley
Director
Bulley-Hewlett & Associates
www.bulley-hewlett.com
Cary, NC USA
888.468.4880 tollfree
-----Original Message-----
From: Ezra Hall [SMTP:ehall@TOGETHER.NET]
Sent: Thursday, October 07, 1999 12:09 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Intermittent Ignition miss, no start,or rich running, need
help!,LONG
Folks,
We have had our '88 westy for about a month now, and among other things, I
have been battling ignition related issues, and could really use some
assistance.
Since purchasing the vehicle, idle would hunt between ~900-1400rpms. On
several occasions, it would climb to ~2000rpms. It has always sounded like
there is a slight misfiring, but it could just be a characteristic sound of
these engines, I am not sure.
The first two times the engine refused to start, the starter motor would
turn the engine over, but no spark was sent to the plugs. Both of these
times, jiggling connections near the distributor seemed to solve the
problem, and it would start and run as usual. At this point I replaced the
following with new Bosch units:
Distributor
Rotor
Plug Wires
Plugs
Ignition Coil (old one was leaking fluid, new unit from Bus Depot)
Then last Saturday on our way to go camping, the engine started running
rough. It sounded and felt like a cylinder was not firing. This didn't
happen prior to replacing the coil. While idling at stop lights, engine
RPM's would drop very low, and it even stalled once. We stopped after ~15
minutes of driving to pick some apples at a local orchard. It wouldn't
start. No amount of jiggling, plugging, or unplugging of connections
helped.
As before, the starter turned the engine over, but no spark. I had my DMM,
so I checked that the hall effect sensor was receiving power, ~11.5volts. I
couldn't check for output from the hall sender as I didn't have an LED. I
didn't check voltage at the coil. We were almost ready to give up, so I
gave
one last try after moving the gear selector out of and into park several
times. It started! There was a lot of black exhaust which indicates the
injectors were firing, so the hall sender is probably ok unless the
injectors are very leaky. The fuel pump could be heard every time the
ignition key was first turned on. The engine was running, so I disconnected
the Lambda sensor to minimize air/fuel ratio variations to the cylinders
that were firing ok when the engine was misfiring. This helped keep it from
stalling when idling. Fortunately, it started every time for the remainder
of the trip.
I have been driving it every day this week, no starting troubles, just the
same intermittent misfiring which causes poor acceleration and low idle
rpm's. After a bit of searching in the archives I decided to re-soldered
connections in the DME last night. Leads for large power resistors were
definitely poorly wetted. I did not re-solder all connections, just those
to
power devices or anything that looked suspect. Today, I still experienced
intermittent misfiring and poor acceleration. On several occasions, I was
driving with constant throttle position, and all of a sudden the engine
would kick in with more power as misfiring ceased. I also noticed that
while
it is misfiring, the exhaust is black. This is only visible when a light
colored car is tailgating!!
Tonight I checked a few more items. The Air Flow Meter is ok. I bench
tested it with power applied, and checked the output for smooth voltage
changes and no noise using my oscilloscope. I also removed the cover and
used contact cleaner/lubricant on the resistive strip for preventative
reasons. The air temp sensor also responds correctly with a negative temp
coefficient, and appropriate resistance.
The coolant temp sensor measured correctly, although I didn't check it
with the engine hot to see if it opens up, the exhaust pipes are just too
close! How does one probe it with the engine hot? Should I unplug the DME
and measure at the correct pins?
The idle/WOT switch was not operating correctly. Since it was already
adjusted to the limit of its range, I had to remove the throttle body to
bend the switch arm for proper closed throttle indication. I also had to
remove the spring assembly to clean the old caked up grease which was
preventing the throttle from closing all the way. It now works perfectly.
I believe there is still a vacuum leak as a whistling sound can be heard
when rapidly opening the throttle. This can be heard even while driving at
cruising speeds as depressing the accelerator modulates a whistling sound.
I
tried probing with a piece of surgical tubing, but was unable to locate the
leak. What is a good method? I tried pressurizing the intake system, but my
12V compressor is too noisy, and once turned off, the leak can only be
heard
for a few seconds, not enough time to locate it. I tried spraying brake
cleaner while the engine was running, but no areas resulted in a change in
rpm's.
The idle stabilizer appears to work as disconnecting it drops rpm's, but
even after proper idle switch operation was restored, rpm's were a bit high
(~1200). Adjusting the air bypass screw on the throttle body dropped RPM's
down to the correct range (~880) and the idle control loop appears to be
operating correctly now. I suspect a previous owner cranked the bypass
screw
open when the idle control feedback loop stopped working due to incorrect
closed throttle switch operation.
I haven't taken it for a drive yet, but idling in the driveway, it appears
to run steady. However, if I blip the throttle, black smoke results. Is
acceleration enrichment that excessive on these digifant systems? or is
something else awry? Obviously I need to locate the vacuum leak, but that
should not cause a rich condition, but rather a lean condition. I suspect
that it is a result of incorrect AFM bypass adjustment combined with lambda
control loop compensation for the vacuum leak that is causing an overly
rich
situation when I blip the throttle. I can correct this later.
I apologize for any errors in my writing, I am tired... I hope I have
described the problems in enough detail so someone can be of assistance. I
am not sure what to do next. I expect to experience intermittent misfiring
tomorrow as none of the repairs I did tonight should have any effect on
such
a problem. Is it possible that one of the injectors is getting stuck
partially open and it is causing an overly rich condition on one of the
cylinders, which causes a power loss and black smoke?
We have a 5 day weekend planned , starting Friday, so I am desperate to
solve these problems!
Thanks in advance for any assistance!
Ezra Hall
'88 Westy
New exhaust, shocks, brakes, etc....
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