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How do you know if you have a feedback carb?

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And which does not require the oxygen sensor? My car is an 84 GL Wagon 1800 OHV FWD.

And which does not require the oxygen sensor? My car is an 84 GL Wagon 1800 OHV FWD.

 

I don't know if in '84 they had feedback carbs at all yet... but the from what I remember, 4WD do not and 2WD do... but the way to know at that year is to check under the hood. if you've got a couple solenoids, tons of vacuum lines, and an o2 sensor in the Y part of the cat... it's definately feedback.

If you have a carb and an O2 sensor then it's a feedback carb.

If you have a carb and an O2 sensor then it's a feedback carb.

... and the corrollary is that if you do not have an O2 sensor then there is nothing to provide feedback.

 

The feedback carbs aren't really like most other feedback carbs. They have extra tubes that go to off-carb vacuum solenoids rather than have a bunch of electricals on the carb itself.

  • Author

Well here's the crux of my problem....I have hoses up the butt, on my carb but I have no O2 sensor....I searched thoroughly, and there is no sensor. I have been getting about 33MPG highway and like 20MPG city.....Mind you I do a paper route so I do a TON of stop and go and lots of idling....This doesn't sound that bad to me for a car with no O2 sensor that is suppoesd to have one.

I really don't think you are supposed to have one. If you were there would be a big hole in your Y pipe where one should be. That is really good milage.

The feedback on the carb does not affect it to a large degree. It uses a pair of vacuum solenoids (at least on the earlier 2-bbl carb) to allow extra air (or reduce vacuum signal) into the idle circuit and into the main circuit to lean them out. The duty cycle is varied on these solenoids by the ECU to alter the amount of air allowed into the circuits.

 

The O2 sensor would be, if anywheres, right in the Y of the Y-pipe, underneath the passenger side axle. Another thing that you could check for is the presence (or not) of the ECU under the steering column, and/or the duty solenoids behind and to the left (driver's side) of the carb; should be a pair of metal clips and some smallish plastic devices clipped into them.

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