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1993-97 Gen II Small Block V8

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Old 07-18-2006, 03:23 PM   #1
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Default Tran am LT1 O2 sensor questions

I am going to change the Oxygen sensor on my LT1 in a firebird and have a few questions

Where exactly is it?
Is it hard to get to ?
I read someplace there is a precat or aftercat one? WTF is that all about?
What tools do I need to change it?

Approximately how much does the O2 sensor cost?

And is this sensor important to the operation of the car?
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Old 07-18-2006, 03:49 PM   #2
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Quote:
Originally Posted by z28fan
I am going to change the Oxygen sensor on my LT1 in a firebird and have a few questions

Where exactly is it? been awhile for a stock system, but I'll tr, one is just under the drivers side exhaust header prior the cat, of course one somewhere after it down the line, passenger side is similar but the cat is under the front seat, hence the floorboard hump, one is just forward of that and aft of the cat.
Is it hard to get to ? What isn't on our cars? Yes of course it is, hoping it will not strip any threads and break of course is crucial, I'd use a lot of WD-40 prior cranking on them.
I read someplace there is a precat or aftercat one? WTF is that all about? The pre-cats read the oxygen and tells the computer what is going on in that side, if it's too rich the PCM leans out vs versa. After cat I used 02 simms and forgot what they do, someone will chime in but I think they help read the overall fuel efficenty, emmissions, etc.
What tools do I need to change it?
box end wrench, wd-40

Approximately how much does the O2 sensor cost? Orielly has Bosch for about $54 bucks each.
And is this sensor important to the operation of the car?
Crucially important, if they start going bad you'll notice gas mileage, tunability (it'llrun like crap.
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Old 07-18-2006, 04:01 PM   #3
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Quote:
Where exactly is it?
Is it hard to get to ?
I read someplace there is a precat or aftercat one? WTF is that all about?
What tools do I need to change it?
its on the exhaust. they are before the cat (precat). depending on the year of the car you may also have them after the cat also.

you can change them with a wrench.
yes they are important.

i have a set of brand new precat sensors if you need a set.
pm me if your interested
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Old 07-18-2006, 04:21 PM   #4
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The precat ones are VERY important. The car will not run right if they dont work. The rear or aftercat ones however are not important, they only tell the computer that the cats are working. If they are not there you will get a check engine light for the cats "not working".

You will need a wrench of the proper size, although i believe you can buy a special socket that fits oxygen sensors (I could be wrong), and lots of wd40.
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Old 07-18-2006, 04:49 PM   #5
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You will need a wrench of the proper size
lol...
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Old 07-18-2006, 05:24 PM   #6
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It would be a great help to include the year of your car next time as it will change the info that is given.


Most of this was covered, but i'll just answer them anyway..



Quote:
Where exactly is it?
Not it, They. You have either 2 or 4. 93-95 has 2, one in each exhaust pipe of each side of the motor. 96-97 has 4, 2 the same as 93-95, and then another after each cat. Simply start at the exhaust port, follow the pipe back, and you will find them.


Quote:
Is it hard to get to ?
Relatively. They are kind of in a bad area. They are not impossible, but they will require a little bit of work. Experience says that the pass side is more difficult then the drivers.


Quote:
I read someplace there is a precat or aftercat one? WTF is that all about?
Pre cat (upstream), are the 2 before the cat. They read the amount of 02 in the exhaust stream, and give this info to teh PCM. The PCM uses this information to add or subtract fuel from the motor, in order to maintain a fuel ratio of 14.7:1 which is best for general power and fuel economy, as well as emissions control.

the post cat )down stream) which again are only on 96-97 cars, are simply there to test the converter. They compare readings with the front 02's to make sure that the cat is in place and functioning.


Quote:
What tools do I need to change it?
They are all 7/8" hex bolsters. They will probably be stuck, and penetrant will be your friend. You can use a 7/8" wrench if you like. You "can" cut the wire and then slip the box end of teh wrench in for a little better grip. There is also a special slotted socket that you can pick up which lets you put a socket and ratchet on it, while the wires go through the slot. These can tend to twist and slip, due to the slot, but sometimes it's the best you can do.



Quote:
Approximately how much does the O2 sensor cost?
Roughly about $60 each. Do yourself a favor and ONLY buy a factory AC delco sensor. Aftermarket sensors tend to cause problems.


Quote:
And is this sensor important to the operation of the car?
Fronts are very important for the reasons listed above. If faulty, they can decrease power, fuel mileage, hurt emissions etc etc etc. Treat them like a tune up part, which means that they should be replaced every 50K miles or sooner.
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Old 07-18-2006, 05:45 PM   #7
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car is 1997 - and has 130,000 on it - I Am thinking that it is time to have to change them.

Vehicle seems to run ok for the most part- check engine light comes on though, I disconnect bettery for a while and can go a week or so before it comes back on.
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Old 07-18-2006, 05:53 PM   #8
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you should take the car to autozone or whatever and have them test the check engine light, and that will tell you why the light came on. Your light might be on for an entirely different reason, and why replace something/spend the money when they arent even bad.
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Old 07-18-2006, 06:13 PM   #9
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regardless, he needs to change the 02's.

however, there could be several other codes in history as well.
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Old 07-18-2006, 06:28 PM   #10
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Codes In history? What does that mean? Sound like it could be something bad.

Between the impossible plug wires, Hard to get at O2 sensors and that damn Engine light - I'm going to go back to the world of carbuartors.
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Old 07-18-2006, 06:38 PM   #11
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If any of the sensors on the motor detect a problem (misfire, bad o2 sensor signal, so on and so forth) it will set off a code. Those codes will be stored in the computer of the car. You can take the car to autozone and they will plug a hand held programmer type thing into the car, and it will read the codes. Which will tell you why the check engine light is on.
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Old 07-18-2006, 06:45 PM   #12
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Ok thanks- Here is another question, I believe (from what I have read elsewhere on the net) that I havebee resetting my computer - the unhooking battery bit for a day, anyway it seems to temporarily take the service engine light off.

By doing this does it take the codes in history and delete them from memory?
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Old 07-18-2006, 06:48 PM   #13
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yes, before you take it there drive it around for a cupple days so the codes are in the computer.
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Old 07-18-2006, 06:52 PM   #14
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Ok thanks for your input and the information.

Anything else that any has to add about O2 sensor on these lt1's ? I'm listening.
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Old 07-18-2006, 06:52 PM
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02, 1998, 97, bad, change, code, drive, firebird, give, lt1, o2, oxygen, precat, readings, sensor, ttops


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