1997 GC repair adventure

1997 GC Laredo 4.0L I6 with about 97K on it. All started with a check eninge
light and a LOT of exhaust noise. Pulled the code and got a 51- O2 sensor sez
lean so the fuel system is dumping gas into the engine, which has caused the
cat converter to overheat and go to pieces. While I'm down there, I discover
that the exhaust manifold is cracked (suprise) and I figure the leak has
caused a faulty O2 sensor reading. I replaced the exhaust with a Thorley tri-
Y header, a Magnaflow high flow converter, and a flowmaster series 70. (If
you have a typical Jeep exhaust manifold crack I HIGHLY recommend this
upgrade- email me if you want to hear more about it) Also replaced the
downstream O2 sensor- with a Mopar- since I was replacing the cat. Didn't
replace the upstream one because I used the stock head pipe. Also replaced
the blackened spark plugs. Ran a can of additive thru the gas to clear out
the carbon. After all that I still have my code 51. I took the Jeep to the
dealership who helpfully charged me $165 to tell me that there was nothing
wrong- my upstream 02 sensor was "lazy."

So I replaced the upstream O2 sensor today and so far the light is out BUT
while I was under there I discovered that there is a vacuum line running from
the front diff that is just hanging loose. I wouldn't swear I didn't knock it
loose during the exhaust replacement, but I've looked everywhere and can't
find a vacuum port for this hose to fit on. My 2 questions are this: 1) Does
anybody out there know where the vacuum line from the front diff is supposed
to connect and 2) What is the likelihood that the vacuum leak is causing my
lean condition.

Thanks for any help! Stu

That's no vacuum line, it's a vent line for the axle. At least on a
Wrangler, that line runs up along side the radiator on the driver's side
which is probably similar to your GC. Look for some plastic snap-in
pieces over in that area which are there to hold that hose.

stupor0420 wrote: I discovered that there is a vacuum line running from
> the front diff that is just hanging loose. I wouldn't swear I didn't knock it
> loose during the exhaust replacement, but I've looked everywhere and can't
> find a vacuum port for this hose to fit on. My 2 questions are this: 1) Does
> anybody out there know where the vacuum line from the front diff is supposed
> to connect and 2) What is the likelihood that the vacuum leak is causing my
> lean condition.

--
Jerry Bransford
PP-ASEL N6TAY
See the Geezer Jeep at
http://members.cox.net/jerrypb/

it is run up by the steering gear and it's just a vent tube for the front axle

stupor0420 wrote:

> 1997 GC Laredo 4.0L I6 with about 97K on it. All started with a check eninge
> light and a LOT of exhaust noise. Pulled the code and got a 51- O2 sensor sez
> lean so the fuel system is dumping gas into the engine, which has caused the
> cat converter to overheat and go to pieces. While I'm down there, I discover
> that the exhaust manifold is cracked (suprise) and I figure the leak has
> caused a faulty O2 sensor reading. I replaced the exhaust with a Thorley tri-
> Y header, a Magnaflow high flow converter, and a flowmaster series 70. (If
> you have a typical Jeep exhaust manifold crack I HIGHLY recommend this
> upgrade- email me if you want to hear more about it) Also replaced the
> downstream O2 sensor- with a Mopar- since I was replacing the cat. Didn't
> replace the upstream one because I used the stock head pipe. Also replaced
> the blackened spark plugs. Ran a can of additive thru the gas to clear out
> the carbon. After all that I still have my code 51. I took the Jeep to the
> dealership who helpfully charged me $165 to tell me that there was nothing
> wrong- my upstream 02 sensor was "lazy."
>
> So I replaced the upstream O2 sensor today and so far the light is out BUT
> while I was under there I discovered that there is a vacuum line running from
> the front diff that is just hanging loose. I wouldn't swear I didn't knock it
> loose during the exhaust replacement, but I've looked everywhere and can't
> find a vacuum port for this hose to fit on. My 2 questions are this: 1) Does
> anybody out there know where the vacuum line from the front diff is supposed
> to connect and 2) What is the likelihood that the vacuum leak is causing my
> lean condition.
>
> Thanks for any help! Stu
>

Yup, that's the vent tube for the front axle. If you can't find the clips
that
hold it in place, secure the free end up so that it is above the axle height
(prevents gravity from possibly draining your dif.).

T

TM wrote:
> Yup, that's the vent tube for the front axle. If you can't find the
> clips that
> hold it in place, secure the free end up so that it is above the axle
> height (prevents gravity from possibly draining your dif.).

The clips are molded into the side of the airbox.
Mine broke and I wound up using a ziptie onto one of the hard
lines.

--
DougW