How stable is the air-fuel mixture on gauge?

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Johnooot
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How stable is the air-fuel mixture on gauge?

Post by Johnooot » Thu Jan 23, 2020 11:41 am

I'm wondering how stable, or erratic, the air-fuel mixture display is on an Innovate Motorsports MTX-L AF Gauge (or similar wideband device), specifically on a properly running 2 litre. Bonus points if you can describe the same on a Cali 2 litre.

The reason I'm asking is that mine is, and always has been, very erratic. Typically bounces from slightly rich to highly lean. I know this is not right and as I troubleshoot I want to get an indication of what I am aiming for. I have no difficulty starting or running, and gas mileage is great.

Thanks.

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asiab3
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Re: How stable is the air-fuel mixture on gauge?

Post by asiab3 » Thu Jan 23, 2020 10:25 pm

Hi there,

Got a video of the gauge in action? My buddy's bus with the same gauge is down at the moment… But even with his mega dual carbs, his 2L engine was relatively steady on the gauge.

Where is your O2 sensor located, and did you have to extend the sensor wires to accommodate the vast expanse that is a Volkswagen bus?

Robbie

Check the 1:30 mark here, it's a digitally glitchy representation of how smooth they are when I've used them. :)
https://www.youtube.com/watch?v=euUi3_PCF9I
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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Johnooot
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Re: How stable is the air-fuel mixture on gauge?

Post by Johnooot » Fri Jan 24, 2020 7:03 am

Hi,

Thanks.

If that YouTube video is representative of what a normal 2.0 litre looks like (carbed or FI), then I have really significant fluctuation.

This video is what mine looks like when simply cruising down the highway at about 40 or so MPH. Because of the slow frame-rate of my camera, lots of detail not showing, but it will give you an idea of the range that is being displayed. Given that the van starts and runs well, and that gas mileage is good, the first order of business will be to determine if I have a gauge issue, or a variable fuel mixture .... (https://photos.app.goo.gl/N8otdfK9sCefLATT7)

The O2 sensor is located in the back of the cat, and yes, I have the long run from there to the dash using their extension cable.

82 Vanagon - cali emissions


John

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asiab3
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Re: How stable is the air-fuel mixture on gauge?

Post by asiab3 » Fri Jan 24, 2020 4:46 pm

While the numbers are blurry, I'd say the outer LED "gauge" is still fluctuating too much.

Is it possible to get the O2 sensor in before the cat? Post-cat sensor readings can do all kinds of whacky things, plus they usually read leaner than actual combustion exhaust content in my experience.

I would wager gauge or wiring issue first, but I'm not sure what a cat near the end of its life would show up as…
Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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Johnooot
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Re: How stable is the air-fuel mixture on gauge?

Post by Johnooot » Fri Jan 24, 2020 7:07 pm

I should be more clear ... the wide-band O2 sensor is upstream (before) the cat (as is the factory narrow-band O2 sensor)

* the cat is hollow so it's well past it's end of life ... ;)

J

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Amskeptic
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Re: How stable is the air-fuel mixture on gauge?

Post by Amskeptic » Sun Jan 26, 2020 6:36 am

Johnooot wrote:
Fri Jan 24, 2020 7:07 pm
I should be more clear ... the wide-band O2 sensor is upstream (before) the cat (as is the factory narrow-band O2 sensor)

* the cat is hollow so it's well past it's end of life ... ;)

J
Wide fluctations in gauge readings point to possible intermittant electrical noise (contact) or holey exhaust (unlikely in this case) or a sensor too close to outside air (unlikey here).
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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