Oxygen Sensor: Yay or Nay?

[childofthewind]

Hello. Please forgive me if this is the most obtuse question in the world.. but, I'm super confused and am hopeful someone will set me straight on here.

To the point: I've had two mechanics disengage my o2 sensor (one on the east coast actually cut the wire). Part of the work I was getting was on starting issues.. and, they went away when I got my van back but I wasn't informed that my o2 sensor was obsoleted so I didn't pay it any mind. When another mechanic looked at my van this fall he was like "hmmm... someone cut your o2 sensor wire.. interesting". He basically said my gas mileage would be much better with it.. can't remember if there was anything else essential it does, though. So, he reinstalled wiring and a new sensor. The van ran fine all through the Southwest until I came back up to Portland where it began to have a very rough start in the morning. It would start on first turn, stall, then would only start again with the gas pedal held down. It ran rich for a little bit and I had to keep it going; it wouldn't stay running on its own. This cleared up in about 3 or 4 minutes.

When I brought it to mechanic in PDX and told them of this issue they returned it with o2 sensor disengaged and it started fine. He said it's unnecessary..

So... what does the o2 sensor do, exactly? Is it important? do any of you run your van w/o it? Is the diff in gas mileage that bad? Am I harming anything else by not using it?

Thanks and sorry again if this is the dumbest question ever.
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1987.5 wolfsburg hardtop; 2.1

“As for me, I am tormented with an everlasting itch for things remote." - Melville

[seanjenn]

O2 sensor=yay
You need it for the van to run correctly.
The eastern mechanic who replaced it may have used a cheaper version to try and save you some cash.
Although, even the Bosch version, which is what should be used, is not expensive. Anyway, if he did instal the lesser version, maybe it self destructed on your way back to PDX. Or, maybe there is a slight issue with the fuel mixture at cruising speed which could cause a sensor to go bad way before its time. I believe the service interval for O2 sensors is something like 15K miles? Somebody correct me if I'm wrong, guess I need to look that up.

I don't reccomend going back to the PDX "mechanic" who said you don't need it. There has to be some solid Vanagon shops in your area.
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1987 GL Sunroof
2.1 4 spd

[eeebee]

O2 sensor is an important component for a properly running engine. It is sometimes disabled to aid diagnostics. The fact that it runs poorly when cold points to another problem because the o2 sensor is supposed to be ignored during cold start. Often a bad temp2 sensor will be the problem. It is cheap and easy to replace.
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Eric

1987 Vanagon Wolfsburg Special Edition
GoWesty 2.3

Democracy is the recurrent suspicion that more than half of the people are right more than half of the time.

[SCM]

The O2 sensor's job is to tell the FI system how rich or lean to make the air:fuel mixture when the vehicle is at operating temperature. When the engine is not up to op temp, the FI systems defualts to a more rich mixture until the Temp2 sensor tells the FI "brain" to start listening to the O2 sensor instead.

So, eebbee is correct, the O2 sensor doesn't come into play until the engine gets warm and the Temp2 sensor notifies the brain (ECU). When my O2 sensor went bad I could drive just fine for the first 2 miles without noticing any problem. Once the motor was warm is when it would run poorly.

If a bad O2 sensor is causing your van to stall etc, unplugging it will fix that problem because the brain defaults back to that rich mixture - but your van will then run rich - making the fuel economy decrease and eventually plugging your catalytic convertor if not fixed in time.

O2 sensors last quite a bit longer than 15k miles, I think the service interval is more like 50 or 60k and even than that's more of a recommendation as they might not really be bad yet.

Accidentally pouring/spilling/leaking antifreeze onto your O2 sensor can kill it.
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'91 Westfalia GL Automatic (GTA "Turbo" Rebuild w/Peloquin) and 2.3L GoWesty Engine

[childofthewind]

Thanks for the replies. I recently replaced tempII sensor.
Also, I think I answered one of my questions, what does the o2 sensor do, on my way home just now. I have had a tiny hole in one of my coolant hoses (temporarily patched with duct tape but still leaking a little) and today, after plugging in my o2 sensor, my led light started to blink after awhile. I'm assuming this was the computer saying somethings not quite right back there. Before I wasn't getting any warning signs on the dash. This is also one of the jobs of the o2 sensor, yes? or are they unrelated?
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1987.5 wolfsburg hardtop; 2.1

“As for me, I am tormented with an everlasting itch for things remote." - Melville

[SCM]

[randywebb]

dunno re Vt. but PDX has smog checks - if your vehicle is subject to them, then it will not pass w/o the O2 sensor in operation

cost is ~$60-$70 for the part - it might be rusted in there, so start spraying it with Kroil now
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1986 2.1L Westy 2wd Auto Trans.

[joseph928]

The o2 one from bosh , the right one is high$, get the one with the wires you splice in, the cost is a 1/4 of the other one .
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1987 syncro westy tin top sun roof , GW2.3, rear locker, decoupler, Gary Lee tire rack & winch mount, lift, south african grill, big brakes , rhein alloy ,15 BFG AT, Fiamma 10 foot awning ,140 watt rear 85 watt front solar , mppt, truckfridge, automatic fire extinguishing system, tencent oil cooler, And a RMW SS exhaust! - 1971 bug convertible 1776 engine- 2010 Subaru turbo - 1993 Toyota 4x4 truck - 1999 Harley 95 CI, big bore, Andrews cams . Also 80-84- vans. Stock 65 sunroof bug.

[zippyslug31]

vermontgirl, you have a PM comparing notes on PDX mechanics.

FWIW, I had the same result from a local shop.... don't really want to share who it is; if you've taken your van there then you already know that's one of their SOPs.

I started taking my van to a new mechanic and they do NOT disconnect the sensor and I've been extremely happy with them and their repairs.
I WILL say who this new mechanic is since I think they are great: Percision Motor Car on Grand Ave. Darrel rocks!
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previous:
'80 westy
current:
'90 syncro westy 2.5L subi, triple knob, 16" wheels.
'84 sunroof van, 2.1L motor.

[RGS Paul]

Slight tangent but…

You didn't drive with the angry blinkey light of death on without checking things did you? There are 2 warning lights you MUST obey, the alternator light and the temperature light. If either of these come on you should shut off the engine immediately and pull over to diagnose why. If the alternator light is on there is a chance that the belt slipped off and the water pump is no longer turning, keep driving and you stand a good chance of cooking things. If the temp light comes on you either 1) have no coolant in the engine and are about to destroy things or 2) are over heating the engine and are about to destroy things. Either way you need to find out what is going on. It could also be electrical gremlins but do you want to bet your engine on that?

Paul
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'87 Syncro 7-Pass. Adventure Touring Vehicle
"Simplicate, then add lightness." Colin Chapman

[childofthewind]

[childofthewind]

[RGS Paul]

Finestkind.

Paul
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'87 Syncro 7-Pass. Adventure Touring Vehicle
"Simplicate, then add lightness." Colin Chapman