O² Sensor


imported_JohnB

New member
FROM THE CHAT ROOM:

I ordered an O2 sensor from Bus Depot and it was only $40.00 The one they had in stock was $l94.00--quite a difference.

The VW technician told me they were expected to splice the old plug-in onto the new O2 sensor, as the plugs didn't match. I told them to go ahead and put in the complete O2 sensor they had in stock, because they said that the one I got was actually for a Ford, and I shouldn't take a chance with a new
engine.

chinook
 

imported_JohnB

New member
Capt. Mike:

O2 sensors are actually quite generic. ALL are Bosch patent and have to be Bosch licensed. There are about three different types -- single, dbl. & triple wire.

There may also be a couple of different threadings & seats. but within a type, the differences are usually just the harnesses and plugs. Obviously a VW OE would just plug in; a generic aftermarket would require the splicing. Net result is the same. $194 is high -- VW list is $172.40.

I personally get a Bosch, P/N 13 931, priced about half-way in between; it will have the correct harness & plug.

All within a type should work identically and would have no effect on a "new" engine -- more likely a lazy tech didn't want to do the splicing or was afraid his splice wasn't good enough. Of course at a dealer, you'd be expected to pay the splicing labor, probably ¼ hour.
 
Last edited by a moderator:

Capt. Mike

Moderator
The 0² sensor detects variations in exhaust gas content and sends a correction signal to the FI control box, which then adjusts mixture. This is done on a continuing basis. Thus it is normal for an FI engine to "hunt" at idle -- change RPMs slighly up & down as the system constantly adjusts. This is a sign of a working controller & O² sensor.

However it should not hunt excessively; maybe 50 RPM or so. If it's swinging several hundred RPM, you have other more serious problem. Likewise if it changes idle RPM a large amount after warming up.
 
Last edited:

elyot

New member
I had a VW Mechanic in Brandon Manitoba recommend I disconnect my O2 sensor due to excessive exhaust leaks which were causing problems. He said it would stabilize things and the F1 would set itself to a default value. He quoted me $1800 in parts which I couldn't handle so I kept patching leaks all the way home. I'm currently waiting for a $400 exhaust system from The Bug Shop in Delta BC. In the meantime, any comment on running with a disconnected O2 sensor as recommmended?
 
Last edited by a moderator:

Capt. Mike

Moderator
The mechanic is correct in that exhaust leaks will defeat the operation of the O² sensor and may cause the vehicle to run too rich or lean while it tries to compensate for a false oxygen level in the exhaust.

"The varying voltage is measured by the injection system's control unit., which alters the injector-open time . . ."

-- VW Type II manual supplement.
He is also correct in that the FI system will run at a default setting, but what then occurs is the system can no longer compensate during the too lean or too rich conditions normal driving creates. Thus as an emergency measure, I concur, but I would not consider doing away with it after the new exhaust system is installed.
 
Last edited:

Capt. Mike

Moderator
Gary B. Dixner

Member posted 09-13-2000 09:37 PM

My neighbor has an 89 Westy with automatic. Occasionally, about 5 minutes after he starts it it coughs and sputters, throws out a lot of blue smoke. The other day he got stuck in a valley and couldn't go either way up the hill til he finally went up one side backwards. Seems like it's running too rich when it does it but it only happens once in a while. He drove it to the nearest VW dealer (about 75 miles). Ran fine. Left it there for 2 days. They couldn't find anything wrong. Ran fine on the way back too. It it runs true to form it will do it again at most inopertune time. Any thoughts?
IP: Logged

Gary B. Dixner

Member posted 09-14-2000 01:47 AM

Sorry, I believe I jumped the gun again. Did an archive search and it sure sounds like Vanagon Syndrome. Will tell neighbor to call the dealer (his van's still there) and suggest they perform tests as described. Don't understand why they didn't know about it. Will report back. Thanks
IP: Logged

Gary B. Dixner

Member posted 09-18-2000 06:58 PM

I made hard copies of info from this site re: Vanagon Syndrome. Dealer located the service bulletin and felt it may not apply because van would act up after only running a short time, not after continued running at higher speeds. Elsewhere in this site symptoms also indicated possible problems with oxygen sensor. That turned out to be the problem. Dealer replaced, lightened my friend's wallet, and it runs fine now. We're about to take a trip. Will let you know if any further trouble. If it hadn't been for your info. the van would not have gotten fixed. Thanks
 

Capt. Mike

Moderator
Transferred from Archives.

Oxygen Light

Gary Clark (gclark7@flash.net), 5/6/00 (10:06 AM)

Hi, I have a 1985 Vanagon Westfalia that is in great shape and runs fine. It has 92,000 miles on the odometer. The oxygen light came on and stays on. I think it is telling me its time for a dealer checkup. Is there any way I can turn it off? This may be a coincidence but it happened right after I filled it with 93 octane gas and put a can of fuel injector cleaner in the tank.

Gary

Capt. Mike Soehnlein (capt.mike@mindspring.com), 5/8/00 (5:24 PM)

The light is on because you were supposed to change the Oxygen Sensor at 90,000 miles. That is a standard service item. After changing the sensor, the mechanic will reset the light. Instructions for both are in the Bentley shop manual.

Read the thread on Gas Octane on the TIPS board; you are wasting money with 93 octane AND it won't run as well. Higher octane gas is HARDER to ignite and the Westy was designed for 87 octane.

Capt. ? O2 sensor in non-standard exhaust

John Branstrom (Blitzrider@aol.com), 11/20/99 (4:50 PM)

I have a 81 vanagon with a non cat. exhaust system and there is no where to mount the O2 sensor. The rest of the motor is stock fuel injected (calf. model) and I would assume that it should have a O2 sensor for the injection system to function properly. I was going to drill and tap a hole in the manifold as close to the muffler as possible. Any ideas?

-- John Branstrom

Clifford Gottschalk (CGOTTS@juno.com), 12/6/99 (11:56 PM)

I used to own an '81 Vanagon Westy and can tell you, especially if it is a California Model, that all of them were cat models. You probably have an after market exhaust or someone has done some interesting modification to delete the cat.

Most of the cats had an O2 port on it where the sensor would fit. Putting an O2 sensor into the system doesn't necessarily mean it is going to operate properly, especially without the cat.

If you don't have a cat, unplug the O2 sensor from the wire harness, and leave it at that. The ECU (fuel computer) will revert to a default mode (if the O2 sensor goes bad, will bypass its readings and run slightly richer to prevent a too lean and overheat condition). You will find that it will probably run pretty good without it, but maybe a problem if you have to do emission testing etc.

Does your exhaust also have the EGR filter and small pipe going to the intake manifold? This is also a necessary item for a proper exhaust system installation for your year. If you don't have to worry about emissions, and the above items are missing, then if it runs good, don't fix it. The earlier buses with similar FI systems, still ran good and didn't use those items either. Hope this helps and good luck.

--Cliff
 

Capt. Mike

Moderator
light?
Thanks, Matt

Jollymon Junior Member # 647 posted 06-10-2001 12:27 PM

No it is just a Elapsed milage counter that is driven off the speedo cable that initiates this light. There is a picture of this in the Bentley on 90.15 there should be a button protruding out of this device to rest it. (On some, it is countersunk into a protector and requires a small pin-punch or the like.) It is advised that O2 Sensors do have a limted effective life and it may be a good practice to replace the O2 sensor based on this. A sensor just gets to be slow to repond as it gets older be cause of fuel adatives etc so a new sensor should make your vehicle cleaner and not give your Cat such a hard time to clean up any excess emissions. Your O2 sensor is a 3 wire heated O2 sensor The heater for the sensor just preheats the sensor for a quicker response it is shown on 97.89. Their is an interesting ploy on O2 sensors. Bosch owns most of the patents on O2 (lamba) one in the same. So all the 3 wire sensors made by bosch are the same. If you puchase the sensor that has the right plugs to just plug it in (13931 Bosch #)it will cost about 160 USD if you by(13913) it will be approx. 35 USD the only diference is you will have to splice the orginal end off your O2 sensor onto the new one (cut of the plug that is on the new one ) about 1 hours work if you are really slow for a savings of 125 USD pretty good wages for an hours work, eh?
 

Capt. Mike

Moderator
Transferred to consolidate same topic.

OXS Wiring

Matt Junior Member # 990 posted 02-27-2002 06:18 PM

I have an 86 westy with a wiring harness problem. I had a bit of an engine fire and have had to rebuild the wiring harness for the LH side injectors and the oxygen sensor. Connected to the O2 sensor, there is a green wire that goes back to the digifant control unit. In that wire is an inner copper core and an outer copper layer that are separated by insulation. Any idea as to which one I attach to the black oxygen sensor wire? What is the purpose of a wire like this?

Thanks,
Matt
 

Capt. Mike

Moderator
It appears you have an aftermarket O² sensor. OE used a R wire for the heater and a black wire for the O² sensor itself (Bentley 97.72, circuit 24-25). The sensor grounds through the body and the heater grounds through a white wire. This means you should have a 3-wire O² sensor.

If you look at the wiring diagram 97.72, circuit 24, you'll notice the brown ground from the ECU terminal #19 has a tap at but not on the green O² wire. This would be consistent with a schematic for the inner wire being the signal and the outer layer tapping to ground, as in most coax systems.

Generic 2-wire 0² sensors are cheaper than the 3-wire with heater, but performance will suffer since it no longer has the heater the ECU is calibrated for.

O² sensors are a service item to be replaced every 90K. Most will go longer. If you're more than ~50K, or unknown, I'd go back to the 3-wire OE or OEM now.
 
Last edited:

jose4ph

New member
I have an 85 Vanagon that is having some idle/warm start problems that I think may be related. My guess due to testing is the oxygen sensor. The van has always started and idled fine when cold. Sometimes when the van is already at operating temperature it has trouble restarting. It sometimes turns over slowly like it is going to just stop turning over and it sometimes just turns over and over and over but never catches. I can give it gas at this point and it will fire up, runs a tiny bit rough for a second and then smoothes itself out. The idle also fluctuates a bit sometimes so I replaced the idle stabilizer. Yesterday in heavy rain, it started trying to stall at every stop. Not sure if the rain has anything to do with it but I read that someone here had that problem. I did spray the oxygen sensor with the hose while idling and it did have somewhat of an effect on the idle. Started to drop to around 300 and want to shut down. Not very consistently though. I recently had 4 new injectors put on the van, I also had the FI system tested which was off according to the mechanic and needed adjusting and a vacuum hose was off but now it is fixed and adjusted to the book according to him. I just drove the van today, it was DRY outside and it was doing the fluctuating idle thing so I unplugged the oxygen sensor wire and it stopped the fluctuation completely. It seems to run perfect when the oxygen sensor is unhooked. Does this sensor need to be replaced? can you run without it? Any ideas here?

thanks!
jp
 

Capt. Mike

Moderator
O²sensors are a consumable -- meant to be replaced at certain mileages. Later models have superceded the O²replacement interval to 90K. But you are also experiencing symptoms that could occur with a wiring problem.

Turning over slowly when hot is a starter/electrical problem not related to the O²sensor.

A 2nd 'wet' problem is discussed elsewhere on the site concerning the throttle valve switching system. Check the other idle or stalling threads.

And, as always, anytime you replace a component like the idle stabilizer and the problem starts, that's usually where I would start looking for the cause.
 
Last edited:

jose4ph

New member
ok, I replaced the oxygen sensor and the idle seems to have settled a bit. It still has a small bit of fluctuation but nothing like before. I mentioned to a vw mechanic the problem and he said that the idle stabilizer can be completely bypassed by just plugging the male into the female and completely omitting the stabilizer. He said he has seen people replace the stabilizer several times and get nowhere doing so...just bypass it. Any thoughts on this?

thanks,
joseph
 

Capt. Mike

Moderator
An 0²sensor is supposed to fluctuate slightly -- that's how they work. They adjust the FI up & down as they detect changes in the CO content of the exhaust. 50 RPM up & down is common.

RE: Idle stabilizer. That's not an 0² sensor question -- post on correct forum (guideline #1). I love mechanics that know so much more than the factory engineers. Read what & why the idle stabilizer is there pg. 24.18!
 
Last edited:

Evans Waldron

New member
I have recently had a lot of wiring work done on my 1983 1/2 Westy (92,000 miles) where the wiring harness, CPU, Fuel Injectors were replaced (The exhaust got too hot which caused the harness to melt caused by a malfunctioning CPU according to my mechanic). Anyway, the van ran fine for a while but then it started to loose gas milage from about 18-19 to 10-11 mpg. I also noticed that it was apparently running too rich as black smoke was comming out the exhaust while increasing the rpm. I called my mechanic and he said to disconnect the O2 sensor and that I could keep it disconnected for months! Since I disconnedted the sensor, it has run fine and the milage has gone back to 18-19 again. The O2 sensor is about 1 year old from the Buss Depot which I replaced along with the exhaust system. My question is will not using the O2 sensor damaging anything? and if not, when will I know when to reconnect it?
 

dbinder

New member
I have an 85 Westy. My O2 sensor light came on and I replaced the sensor with an new Bosch sensor (one wire only). I scoured Bentley and couldn't find where to reset the light. What page is it on?
 
Last edited by a moderator:

Capt. Mike

Moderator
O² sensor indicator lights are a function of the speedometer/odometer. See post above this topic dated 6/10/01.
 
Last edited:

Capt. Mike

Moderator
Transferred to consolidate same topic.

Bill Forst Member posted September 11, 2003 12:16 AM

My '84 started doing the typical Vanagon Syndrome things this summer, loss of power, terrible mileage etc. Being Digijet though, it isn't really Vanagon Syndrome. I disconnected the O2 sensor, and it is running like a top. I couldn't tell from the postings what will happen if I don't ever hook it up again. It is a fairly new O2 sensor, so not likely the problem, but that is first thing I will try if I do need to hook it up again. Any suggestions?
 
Last edited:

Capt. Mike

Moderator
That an O² sensor is new is not a guarantee it's working -- or that there isn't a problem with the O² wiring; test per Bentley. Failure to hook back up means the FI goes to a default mode and the engine cannot adjust to changes in mixture. This can cause it to run too lean (will ruin engine) or too rich (foul engine and not pass EPA inspections). Neither is acceptable. These things are no longer just a matter of meeting pollution standards -- they are an integral part of the FI system and essential to good running and engine health. If the O² sensor is working, then you have a problem elsewhere, perhaps with the ECU.
 
Last edited:

bodhi

New member
I had my O2 sensor light come on a while back and I understand thats a mileage thing related to speedometer/odometer mechanism. It indicates its time to replace the O2 sensor. Well I've done that twice in the last 30,000 miles so I don't need to do it again and beside after last years tune up, the westy is running like a top, great power and 19-20 mpg. Anyway, I just want to reset the light, I've read what the Bentley says to do and I've done it. Still the light remains on. Am I missing something between the lines of the Bentley. I don't plan on taking the westy into the mechanic for a while, but would like O2 sensor light to not be lit......it scares the passengers. Any help....
 

Top