Why is this Vanagon running so rich?

[pinetreeporsche]

A few weeks ago a relatively young mechanic diagnosed my drops of water from (I thought) one side (passenger side), and set out to deal with that. He found that the drips were from head gasket, and the other side had a less advanced case of the same. I thought I'd get it sorted before the warm (camping) weather hit, so had him do a gasket replacement, both sides. When he had it back together, it started almost normally but started dropping out one cylinder or worse- power dropped to more like my old 40-horse Splitty. He poked at it some, couldn't make it any better-- although there was none of that before he did the heads. Driving it the 18 miles home used up almost 1/4 of a tank of gas- mostly sluggish, but occasionally jumping up in power as it the pre-work condition-- getting the revs up. But getting probably 4 to 6 mpg!

Next day I went to the close-to-my-home vintage VW shop with a mechanic closer to my age (70s), and had me put mine on his waiting list-- had to wait 6 weeks because he has so many long-term clients. My turn finally came up there last Wed, and he checked out all the normal things, and spent lots of time- checking the plugs, wires, dist., fuel flow, etc. Clearly running VERY rich- did some of what he could to bring it toward normal. Found the fuel pressure regulator a bit above the spec 29#-- like about 36, but wasn't clear that that caused it to run on 3 cyl much of the time, possibly 2 sometimes. He did swap out all sorts of other things with ones from a well-tuned twin van out in his lot-- like the ECU (main computer), air flow meter, temp sensor, and adid a little adjustment the throttle position sensor. And checked grounds, etc.

SO... it's still running very poor, esp going uphill., and guzzling as before, so I asked him if a Q on the Samba was OK and he said sure- any new insight would be welcome. As mentioned above- he was a young mechanic when the Water-cooled motors appeared in '83, so has close to 40 years with them. And he's always had first-class ratings on public sites. We are not as thick with Vanagon-era master mechanics as on the west-coast; it's over 2 hours to the nearest shop with a similar reputation in VA. Because he didn't have a good fuel pressure regulator to swap to check that suspicion, and it'll take about 2 days to have a new one arrive, he's happy to solicit other ideas- he's modest enough to admit that some useful new clue would be welcome. Does anyone have one?? -Thx

[djkeev]

What year?
What engine?
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Ghia
http://www.thesamba.com/vw/forum/viewtopic.php?t=392473

Vanagon
http://www.thesamba.com/vw/forum/viewtopic.php?p=6315537#6315537

Beetle
https://www.thesamba.com/vw/forum/viewtopic.php?t=482968&highlight=74+super+vert

[Wildthings]

I would bet that the shielding for the coax going to the O2 sensor has shorted to the signal wire. If so its an easy fix.

[Howesight]

I agree with Wildthings above. The process of cylinder head removal involves removing the exhaust system which involves wrestling with the oxygen sensor wiring. That's the smoking gun.
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'86 Syncro Westy SVX

[DanHoug]

[Ahwahnee]

X4 on the short to the coax. Mine did that and mpg dropped into the single digits.

[pinetreeporsche]

[pinetreeporsche]

I passed the 4x opinions about the shorting out, but he had checked that out last Saturday. Any more suggestions will be appreciated, and if he comes up with a winner, I'll share it w/you interested mechanically inclined commenters.

[DanHoug]

persuing the fuel pressure regulator for poor gas mileage is folly.. the ECU will trim back the injector dwell time for any extra fuel squirted due to higher pressure. and the pressure readings are fine in my book.

he really needs to focus on the O2 sensor and whether that signal is getting back to the ECU. he should back probe the sensor to the spade connector and check voltages while running and see if they fluctuate above and below 0.5v every few seconds. then disconnect the sensor and see what the voltages are and how the engine is running. i'd also pull the ECU plug and verify continuity to the O2 sensor lead as well as check resistance values at the ECU for the Temp II coolant sensor.

if still coming up with everything 'normal', it's time for a manifold vacuum check and then a compression check.

if he's been a VW mechanic for 40 years he SHOULD have an ECU plug breakout connector, makes it easy to check parameters while the engine is running.
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-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[DanHoug]

ECU breakout connector... ALMOST as good as having the DigiMatrix mod!

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-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[jlrftype7]

[danfromsyr]

is the water temp gauge working properly ?
it could be possible on a 2.1 to switch the plugs from the temp-II and the Gauge senders
this would give the ECU a bad temp-II reading (why VW didn't use the same resistive values IDK) and could cause it to think it's still operating a cold engine..
which would cause the ECM to ignore the O2 sensor values and stay in enriched fuel mode.

the sender are color coded but I don't recall if the plugs are 'keyed/slotted'
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[kamzcab86]

[DanHoug]

[DuncanS]

There is an engine ground wire fastened to the block between the two DS cylinders. If this ground is compromised you can get this syndrome. But still think scoping out the O2 should be really thorough.

Duncan

[djkeev]

[DuncanS]

Do you know how to remove the temp gauge sender plug? My '91 has a clip on the PS of it and when I try to pry it out, it won't move. Is there a trick?

Duncan

[Wildthings]

On the later ones you just press in on the center of the bale which makes the legs expand. On the earlier ones, I use a dental pick to get under one leg and lift it out of its groove.

[DuncanS]

No wonder. I thought it was a slide out widget. Thanks.

Duncan

[danfromsyr]

Kam, Yes but to DIYs and some mechanics color doesn't always play into it.
especially in the location of the 2 plugs on a 2.1

and don't rule out the factor that the wrong sensor can be but into use
my 91 came to me with 2 sensors of the same color. ran poorly.