Date: Thu, 7 Oct 1999 08:31:03 -0500
Reply-To: Darrell Boehler <midwesty@MIDWEST.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Darrell Boehler <midwesty@MIDWEST.NET>
Subject: Re: Intermittent Ignition miss, no start,or rich running,
need help!, LONG
Content-Type: text/plain; charset="iso-8859-1"
Hi Ezra,
You have done a lot of good diagnostic work. Seems your biggest
remaining problem is running rich. Does your van run rich in open loop ( O2
sensor unplugged) ? If no replace the o2 sensor. If yes check, clean and
shine ground wires on left side of engine near coil and ground strap going
to left head. Check temp 2 sensor (coolant temperature) you need to check
it while it is failing. Attach a wire to it and attach you lcd meter to the
wire and ground. With a warm engine temp2 will read about 0.1 volt and be
steady. Keep an eye on your meter when the problem develops. Try some fuel
injector cleaner in your tank.
With a warm engine using your lcd meter (or scope if you like) check the
o2 voltage with it plugged and unplugged. Plugged it should be bouncing
above and below 0.5 volts. Unplugged it should be about 0.7 volts. Check at
idle and at 3k rpm. Above 0.5 volts the mixture is rich, below 0.5 volts it
is lean. The difference between 0.7 and 0.2 volts is less than 0.1 percent
variation in you air fuel ratio. Good luck with your quest, the tougher the
battle the sweeter the victory. Keep heart camping in a vw is really worth
it all.
Darrell Boehler
Makanda Illinois
Ps. If you need a O2 in a hurry and one for a vanagon is not in your area,
an 88 3.8L taurus will work fine. Just chop off the ford connector and
solder on the vw from your old sensor.
----- Original Message -----
From: Ezra Hall <ehall@TOGETHER.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, October 06, 1999 11:09 PM
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....
>
| 
