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The "Ask a Mechanic" Thread


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ok, so i have been told it is the oxygen sensor but i dont know where it is.

is there a place i can find a diagram for a 1994 chevy Z71 K1500 4x4?

The oxygen sensor(s) is/are located on the exhaust. There is at least one but more likely two or three on that vehicle. There are upstream oxygen sensors that are located before the catalytic converter and there may or may not be a downstream oxygen sensor located after the catalytic converter.

I would start by looking at the exhaust manifolds and seeing if there are any sensors that plug into the exhaust manifold or below that on the exhaust manifold. There are no other sensors that plug into the exhaust, so if you see one, it is an oxygen sensor.

After you find the oxygen sensor(s), you'll need to find out exactly which one needs to be replaced if it has more than one (which it probably does). They will usually be pretty rusty and hard to remove. You'll probably want to spray some penetrating oil on in a few minutes before you try and break it free from the exhaust.

Hope that sends you in the right direction.

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If its a 94 I would assume it only has 1 02 sensor placed before the cat...just a hunch.

Spray that SOB for sure...soak it. If its the original, or if a replacement has been overtorqued, youre in for a battle if its in an awkward spot.

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If its a 94 I would assume it only has 1 02 sensor placed before the cat...just a hunch.

Spray that SOB for sure...soak it. If its the original, or if a replacement has been overtorqued, youre in for a battle if its in an awkward spot.

im so dumb i dont even know what the cat looks like to see the sensor there. i know this sounds horrible but im just a noob at chevy engines. i can turn a wrench well enough but i just dont know the engine.

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im so dumb i dont even know what the cat looks like to see the sensor there. i know this sounds horrible but im just a noob at chevy engines. i can turn a wrench well enough but i just dont know the engine.

It's easy to find. It's the only think that has wires coming off of it that screws into the exhaust. It's probably located before the converter (most look the same) soon after the two downpipes from the exhaust manifolds connect.

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*looking up catalytic converter*

OK, don't worry about the catalytic converter. Just look for a spark plug looking thing that has wires coming off of it that plugs into the exhaust towards the front of the car. Could be visible if you pop the hood or you may have to look underneath. They are easy to replace as long as it isn't rusted into the exhaust.

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you mean where all the spark plug wires go? i just changed that out not too long ago along with the rotor to it.

No, the spark plug wires go between the distributor cap and the spark plugs. Those have nothing to do with the exhaust.

Hold on a second, I'll try and pull up a picture for you.

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This is a picture of a Toyota Prius exhaust, it's the best I can do right now so it will have to work. Down at the bottom of the picture there is an oxygen sensor plugged into the exhaust, right after the catalytic converter. It's the thing with the wire coming off of it and the blue connector (to the left).

PriusConverter_0100.jpg

This is a close up picture of an oxygen sensor installed in the pipe.

PriusConverter_0102.jpg

This is a picture looking into the exhaust towards the oxygen sensor. You can see the sensing device inside the exhaust and the rest of the oxygen sensor outside of the exhaust.

PriusConverter_0103.jpg

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so is this going to be on the top or underneath of the engine? left side? right side?

i dont know too much about engines honestly which is why i was just trying to get a big overview pic of it.

thanks for the help too man..youre a gentleman and a scholar.

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so is this going to be on the top or underneath of the engine? left side? right side?

i dont know too much about engines honestly which is why i was just trying to get a big overview pic of it.

thanks for the help too man..youre a gentleman and a scholar.

I've been trying to find a good picture of your particular car, it's been hard. I believe that the sensor will be underneath the car where the two exhaust pipes that come off the engine merge. Look for something in the exhaust that resembles the sensor in those pictures.

If it's not there, it will be in the exhaust manifold (left or right, I'm not sure) where they come out of the engine.

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ok,

how bad is this for my engine? i can get it done myself but it wont be for a minute...

and how can i get my truck to get better gas mileage? i have a 22 gallon tank and get about 300 miles per tank. i have changed the plugs, wires and air cleaner but what else can i do?

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My dog ate the cord to the mower. I fixed it last year, but have to wind the damn thing each time I want to start it. Then he ate it again this week, AND ate the cord on my g/f's mower. ( I have to leave him in garage during work, but will now be leaving mower in outside shed:doh:)

Leave it plugged in. He'll never eat the cord again.

Of course that's a joke!

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Leave it plugged in. He'll never eat the cord again.

Wanna bet?...I think my idiot dog likes the shock.:chair:

I do use GFI breakers though.

..

Big mike ,you can remove the tailgate,increase tire pressure to the max,and eliminate any excess weight,but changing the way you drive will probably result in the biggest change you can effect.

Look up hypermiling if you want extremes.

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Reminds me of the time when we came home and there was a large puddle of urine right next to a refrigerator cord that had been gnawed. OLS

I'd like to say the dog learned his lesson, but he was a Jack Russell. There is no "learning" involved with that breed.

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Reminds me of the time when we came home and there was a large puddle of urine right next to a refrigerator cord that had been gnawed. OLS

I'd like to say the dog learned his lesson, but he was a Jack Russell. There is no "learning" involved with that breed.

I used to have a rabbit that would hop around the house and chew on wires. One day, I noticed he had black marks around his mouth. Upon closer inspection, I found that they were singe marks. Silly rabbit! :silly:

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I used to have a rabbit that would hop around the house and chew on wires. One day, I noticed he had black marks around his mouth. Upon closer inspection, I found that they were singe marks. Silly rabbit! :silly:

I think my mother lost her rabbit that way around the time the AFL was forming....

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ok,

how bad is this for my engine? i can get it done myself but it wont be for a minute...

and how can i get my truck to get better gas mileage? i have a 22 gallon tank and get about 300 miles per tank. i have changed the plugs, wires and air cleaner but what else can i do?

You can start by replacing that bad oxygen sensor. :silly:

Seriously though. They oxygen sensor reads the oxygen content of the exhaust so that the computer knows how rich (more gas) or lean (less gas) the car is running. If the oxygen sensor is reading the oxygen content incorrectly, it could cause your truck to run too rich and thus wasting gas. You'll probably notice a performance difference as well once your truck has the proper air fuel mixture going to the cylinders.

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And Mike... It can be very bad for your engine depending on how the oxygen sensor has failed. If it's causing the truck to run super lean, it will burn up the catalytic converter and possibly intake/exhaust valves over a period of time.

If you oxygen sensor truly is bad, have it replaced. You'll thank me later.

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is it hurting my engine badly? like i said I can replace it in about a week but I dont want to hurt the truck either.

A week probably won't make a huge difference at all. Every case is different though. It's hard for me to say.

I was looking up prices for oxygen sensors for your truck last night. I forgot to mention, they are remarkably cheap. Something like 30-50 bucks should cover the cost of the part.

Good luck with it.

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Wanna bet?...I think my idiot dog likes the shock.:chair:

I do use GFI breakers though.

..

Big mike ,you can remove the tailgate,increase tire pressure to the max,and eliminate any excess weight,but changing the way you drive will probably result in the biggest change you can effect.

Look up hypermiling if you want extremes.

I thought I heard that trucks are designed to get better gas mileage with the tailgate up. But I guess if you take it off it makes the truck that much lighter.

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