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RCB
Samba Member
Joined: September 05, 2005
Posts: 4143
Location: San Francisco-Bay Area
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 Posted: Fri Apr 10, 2009 1:33 pm Post subject: |
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Congratulations on passing.....another healthy Vanagon /Westy on the road...
Yes the o2 sensor only has one wire but if it has been replace a few times in the Van's lifetime the coaxal wire that it is spliced onto can go bad and cause goofeyness to the way it runs.
Did you get some of your monies back?? The AFM if new must have cost $500.00 or so bucks.... |
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woggs1
Samba Member
Joined: February 22, 2007
Posts: 531
Location: South Pacifica California
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| Posted: Fri Apr 10, 2009 3:02 pm Post subject: |
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| RCB wrote: |
Congratulations on passing.....another healthy Vanagon /Westy on the road...
Yes the o2 sensor only has one wire but if it has been replace a few times in the Van's lifetime the coaxal wire that it is spliced onto can go bad and cause goofeyness to the way it runs.
Did you get some of your monies back?? The AFM if new must have cost $500.00 or so bucks.... |
It wasn't the new AFM, it was the busdepot $149.95 remanufactured one plus $30 deposit. Probably can't return it because it is an electrical item. http://www.busdepot.com/details.jsp?partnumber=410038 A $150 lesson learned.
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4 speed 88 Westy |
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tencentlife
Samba Member
Joined: May 02, 2006
Posts: 10078
Location: Abiquiu, NM, USA
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| Posted: Fri Apr 10, 2009 3:29 pm Post subject: |
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Reading this I was thinking it is the classic problem of inadvertent grounding of the O2 signal lead. The problem isn't the wire from your new sensor, it is the condition of the green coaxial cable it attaches to to carry the low-voltage signal to the ECU. If the signal lead in the center of the coax gets grounded due to damage of the coax, or at the terminal end, the FI will run stink-rich.
There are scores of posts here where people have had this same problem, with simple procedures to test for this condition. Search "green coax" and look for posts by me or dogpilot if you're curious.
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Experience is kryptonite to doctrine. |
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keithwwalker
Samba Member
Joined: May 30, 2005
Posts: 886
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| Posted: Fri Apr 10, 2009 4:08 pm Post subject: |
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| tencentlife wrote: |
| There are scores of posts here where people have had this same problem, with simple procedures to test for this condition. Search "green coax" and look for posts by me or dogpilot if you're curious. |
Yes, one of my links earlier on, linked to another thread I started that showed how awful the O2 connections can get:
http://www.thesamba.com/vw/forum/viewtopic.php?t=286423&highlight=
Here's the old crap:
and here's my new crap:
The big connector is a Molex MX150 which is essentially waterproof (not just the connection but the backside of the insulators as well). It will make future maintenance a snap as well as increase longevity of the connection. The connection upstream connects to the green coaxial wire, which I cut back to the good portion. |
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woggs1
Samba Member
Joined: February 22, 2007
Posts: 531
Location: South Pacifica California
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| Posted: Fri Apr 10, 2009 6:57 pm Post subject: |
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I just picked up the van and it runs sweet!
| tencentlife wrote: |
Reading this I was thinking it is the classic problem of inadvertent grounding of the O2 signal lead. The problem isn't the wire from your new sensor, it is the condition of the green coaxial cable it attaches to to carry the low-voltage signal to the ECU. If the signal lead in the center of the coax gets grounded due to damage of the coax, or at the terminal end, the FI will run stink-rich.
There are scores of posts here where people have had this same problem, with simple procedures to test for this condition. Search "green coax" and look for posts by me or dogpilot if you're curious. |
That was the situation in my case. I put in a new O2 sensor after the van failed the pre-test. Due to my ignorance I thought it was just like any other wire and just crimped it to a connector. When I did that I shorted out the signal wire to the coaxial metallic shield, and screwed it all up. My mechanic called his friend who used to work at a VW dealer in the '80's. My guy described what was happening, and that guy immediately told him what to do. Whowouldathunk?
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4 speed 88 Westy |
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funagon
Samba Member
Joined: March 09, 2006
Posts: 1308
Location: SLC, UT
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| Posted: Fri Apr 10, 2009 10:09 pm Post subject: |
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| tencentlife wrote: |
| The problem isn't the wire from your new sensor, it is the condition of the green coaxial cable it attaches to |
"That's what I said on page one" Funagon replied, gloating. "Glad you got it fixed Woggs!"
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1990 GL 7-passenger
2.2 liter WBX |
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woggs1
Samba Member
Joined: February 22, 2007
Posts: 531
Location: South Pacifica California
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| Posted: Sat Apr 11, 2009 7:10 am Post subject: |
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| funagon wrote: |
| tencentlife wrote: |
| The problem isn't the wire from your new sensor, it is the condition of the green coaxial cable it attaches to |
"That's what I said on page one" Funagon replied, gloating. "Glad you got it fixed Woggs!" |
Your right Funagon, I read it when I was at work, and my brain is pretty much jello at work. Thanks for everyone who gave me good advice, The Samba Rules!!
Thank you
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4 speed 88 Westy |
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Alan Brase
Samba Member
Joined: March 28, 2004
Posts: 4532
Location: Cedar Falls, Iowa
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| Posted: Sat Apr 11, 2009 7:29 am Post subject: |
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How did the low compression come and then disappear and how did this affect the smog test? Was it just induced by them adjusting the valves and eventually the hydraulic lifters sorted it out by themselves?
Al
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Al Brase
Projects: 67 sunroof bug, 67 Porsche 912 Targa, 70 Westy
Dec 1955 Single Cab pickup WANT 15" BUS RIMS dated 8/55, thru 12/55
To New owners: 1969 doublecab, 1971 Dormobile
Vanagons:
80 P27 Westy JUL 1979, 3rd oldest known US
83 1.6TD Vanagon, 87 Wolfie Westy daily driver, swap meet home |
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tencentlife
Samba Member
Joined: May 02, 2006
Posts: 10078
Location: Abiquiu, NM, USA
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| Posted: Sat Apr 11, 2009 8:42 am Post subject: |
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They do that. Adjusting them didn't sort anything out, they did it themselves when the engine was run warm again.
<rant on>:That's why I'm always saying you can't go by comp tests on these unless you control for bleed-down. Comp tests need to be done with a warmed up engine and immediately after shutting it down. Ideally you would do one side, run the engine a few minutes, then do the other side. It's one thing when you know that engine, it's another when it's the first time it's been tested. Rolling into any commercial shop and making any decisions on the results of a comp test is your guarantee that you'll be encouraged to toss a bunch of parts at the thing unnecessarily. God knows how many cyl heads have been replaced on the basis of this faulty info. For the amount of hassle required to assure an accurate result, it's better to simply do a leak-down test instead. It tells you so much more that is valuable anyway, that should be the primary test for engine mechanical condition.<rant off>
_________________
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Please don't PM here, I will not reply.
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tencentlife
Samba Member
Joined: May 02, 2006
Posts: 10078
Location: Abiquiu, NM, USA
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| Posted: Sat Apr 11, 2009 8:55 am Post subject: |
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| funagon wrote: |
When the exhaust is rich one of the first things I look at is the O2 sensor. They frequently go bad in the vanagon. |
When it's a little rich, yes, you should check for voltage from the sensor.
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You also need to look at the wire that runs to the O2 sensor. It is coaxial, meaning it has a sheath/covering that carries a signal and should not make contact with the inner wire. Often where the sheath terminates it becomes frayed and contacts the exposed inner wire.
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You get credit for pointing to the problem, but for the interests of posterity some clarification is in order. It is the center core wire that carries the signal. The sheathing is grounded and intercepts RF noise from the ignition coil, primarily, since the coax travels so close to it, but also shields the core wire from the other RF sources (sparking in the distributor, and especially the alternator) that would drown out the signal.
The sheath is grounded at one location. If the sheath and signal core come into contact, then, the core wire gets grounded. That is what makes the thing run stink-rich.
This problem is actually acknowledged in the Bentley FI section, by the presence of a simple test: when the engine is warm and running closed-loop (integrating the O2 signal), you simply jumper the O2 connection to ground. If the idle changes, and goes noticeably richer, then that means everything is OK with the signal circuit. If it doesn't change, then that means that that makes nothing change, so therefore the signal circuit is already shorting somewhere to ground.
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https://intrepidoverland.com/vanistan/
Please don't PM here, I will not reply.
Experience is kryptonite to doctrine. |
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