idle fluctuation up/down running RICH 84 Digijet 1.9L

[peaceman]

HELP please. I have searched and have only found bits and peices on the forum.
So my 84 Westfalia 1.9 digijet idle would fluctuate up and down once the engine was warm. It would not change- constant up and down.
I found a bad connection to the O2 sensor and that fixed the problem.
NOW it runs way rich. I have unplugged the O2 sensor and it still is blowing black smoke. the new spark plugs are black and sometimes wet with fuel.
Now it wont start.
PLEASE HELP. Should I turn the AFM a couple clicks clockwise?
SHould I hook up the O2 sensor or not?
WHere can I find info on troubleshooting this stuff. THe bently manual is useless since I do not have a graph meter YET.

PEace,
Jeff

[Terry Kay]

It sure sounds like the throttle positioning switches.

The Bentley really is terrible for diagnosing & resolving injection problems.

Take a ride over to the samba.com Vanagon parts section.

I have a Digijet factory injection manual available that will help you dial in your 84.

If you can't find the manual there,go to;

http://community.webtv.net/VanStuff/VanagonWestfalia
_________________
T.K.

[tencentlife]

Sounds like a classic ground fault in the O2 sensor signal circuit. I'm just going to copy the procedure here from another thread, to save you having to hunt around. With an ohmmeter this is pretty easy to check, and usually easy to repair unless the fault is in some buried location:


Check it exactly like this:

Disconnect the single-wire signal lead of the O2 sensor from the green coax. You will find the connection hanging between the left cylinder head and the left wall of the engine bay.

(If your van has a three-wire heated sensor, you can leave the two-pin heater plug for the sensor connected; it has nothing to do with the signal circuit).

Leave the disconnected end of the green coax hanging free. Make sure it won't touch ground inadvertently.

Ignition off! Disconnect the multi-pin connector from the ECU.

Put VOM in ohms mode, lowest-range if not auto-ranging.

Connect one VOM probe to the free end of the coax center wire.

Touch the other probe to ground. You should only ever see infinite ohms (open circuit). This verifies that the signal wire is not inadvertently shorting to ground. With the probe still attached, move the coax wire around a bit and watch that there is never any continuity to ground.

Leave the probe connected at the signal wire of the coax. Now touch the other probe to the O2 signal pin at the ECU harness plug. You should see zero ohms. This confirms that you have a continuous signal circuit.

Pull the small rubber boot back from the double-male connector that should be on the free end of the coax. Now take the first probe from the signal wire at the end of the coax, and touch it instead to the coax sheathing braid. Touch the other probe to ground. You should see zero ohms. This confirms that the noise-suppressing sheathing is properly grounded (it is grounded up near to the ECU harness connector).

That is the complete, isolated test of the signal circuit and noise-suppression.

Don't concern yourself with checking the resistance of the O2 sensor to ground (irrelevant), the resistance of the O2 signal circuit thru the ECU (also irrelevant). Confine your tests to the signal coax in isolation.

The area to inspect very closely is the free end of the coax. Many times the ground fault is due to the fine wires of the sheathing braid fraying and coming into contact with the signal core wire or connector. Trim back the sheathing and make sure not a single braid wire can reach any part of the center wire.

If the fault isn't there, sometimes the coax has been mashed or pinched somewhere, causing internal damage where the braid is forced thru the center wire's insulation. You should do a careful visual check of the whole coax run looking for damage.


Now, there's also a quicky functional test for grounding of the O2 signal circuit with the engine running and warmed up, everything connected as normal including the O2 sensor (this test also works with the o2 sensor disconnected). Under those conditions, you take a jumper from ground and connect it to the O2 signal connection (or simply ground the free end of the coax signal wire with the sensor disconnected). Whenever you ground the signal wire, the engine should noticeably alter speed and run stink-rich. If there is no change, then there is already shorting to ground somewhere of the O2 signal. If it does change to a very rich idle, and back to normal when you unground, then functionally all is fine with the signal circuit. This does not confirm anything about the quality of the O2 sensor output, only that the signal will reaching the ECU cleanly.

Don't be tempted, by the way, to ground the free end of the coax's sheathing braid. It is grounded up near the ECU, and to cancel noise a sheath like that can only be grounded in one location.


_________________
Shop for unique Vanagon accessories at the Vanistan shop:
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Please don't PM here, I will not reply.

Experience is kryptonite to doctrine.

[climberjohn]

Hot Rod,

In under 1 hour you got answers from Terry K and Tencent.
What more could ask for on this great forum?

Good luck!

(For what it's worth, I recently had the same problem in my 86 with Digifant. Adjusting the Throttle Positioning Switch (TPS) fixed it for me.)
_________________
'86 Westy, 2.5 Subaru power
Know your limits. Exceed them often.

[peaceman]

Thank you both very much.
I messed with adjusting the cog wheel on the AFS
swapped out the temperature thermal switch
runs rough and pops a bit now.
The cat was glowing red. Big rich problem. I'll buy the fuel injection book.
So many variables to a running rich problem.
Oh and the idle fluctuation is back. What a drag this engine is.....
If anyone knows of how to obtain a Factory Vanagon repair manual please let me know.
Going to check the O2 sensor now. Thanks Terry and tencentlife.

[tencentlife]

I would point you to Dogpilot's public files where he has the Digifant Protraining Manual you can download, but yours is a Digijet, so only the fuel section is relevant. Nonetheless, the operating principles and a lot of the components are the same, so it might help you understand it better. If you take some time searching here, though, we have collectively written the book on these systems. Bit by bit you can glean a very complete picture of what's going on and ways to check and diagnose almost anything.
_________________
Shop for unique Vanagon accessories at the Vanistan shop:
https://intrepidoverland.com/vanistan/

Please don't PM here, I will not reply.

Experience is kryptonite to doctrine.

[Terry Kay]

<< so only the fuel section is relevant. Nonetheless, the operating principles and a lot of the components are the same,>>

What?

Name one component that is the same--
the distributor, spark plugs, Or the intake boot?

<< so it might help you understand it better.>>

What is going to happen here is that your going to confuse the poster big time.

Digijet & Digifant are night and day apart--- not even close.

What he's goig to be gleaning is a dime's worth of confusion---

Bit by Bit--Little by Little he'll be doing some real gleaning--like a combine.

Good info--
_________________
T.K.

[turbo2cv]

Tencent: the trimming of the coax shield away from the center wire is a great advice. Not found in any book. It worked for me.
Thank you

[tencentlife]

[Terry Kay]

The problem could very well be the O2 sensor, but as soon as the OP mentioned the glowing red converter, in my Aggro- Nomical wisdom, I really believe it is beyond the O2 sensor.
And for the life of me, sure can't figure out why all of the folks all of the time go right for the O2 Sensor first thing, when the switches at the TB mechanically open and close a thousand times a day--every time you touch the throttle they open close, or close & open.
However you want it.

They are like a set of contacts in a points ignition--and usually the first item to wear & fail.
Nobody will even give them a primary adustment first, before playing ring around the rosie, pocket full of posies, removing and replacing insignificant secondary eletrica control item's.

Something is telling the ECU & the injectors to blow more fuel at the cylinder's than they can burn.
The dual switches are a pain at the throttle switches.
set the up first, then you have an engine running base from which to start the other electrcal engine managment tests.

But here's another thought.

If the converter is plugged solid--it'll glow redder than a hot potato--which would cause big time, full time operating problems.

What my corn fed mind is wondering, what happened to the OP and the Van?

Did he get it running OK??
12 of 09 was one hell of a long time ago.
He more than likely got frusrated and bailed.

Been awhile.

Digijet & Digifant are like like apples & marshmallow's--not even close to operating the same.
_________________
T.K.

[downshifting1984]

Hi everyone! 1st, let me say that this site and its contributors are the brst. as i get better, i’ll contribute more. So, any tips on trimming back the o2 sensor coax canle shielding? i need to trim the cable to put in a new connector, and i eant to avoid the signal shorting to ground.

thanks!!