02 sensor question...

[camarorss350]

I just noticed that my jeeps O2 sensor isnt screwed into a bung in the exhaust its just dangling under the car tied up to the transfer case, there was a dynomax muffler and a catco high flow cat installed before i bought the car and i didnt noticed the O2 until now.... will this hurt anything? gas mpg, power, etc? the computer isnt throwing any codes to make the SES light come on....thanks for the help

 

[5-90]

It can - and the HEGO sensor should be reinstalled - since the fuel metering depends upon feedback from the HEGO sensor to monitor AFR and to keep track of how well it's doing.

With the HEGO sensor dangling free, the ECM will read a constant "lean" condition, and try to correct by adding fuel. I'd think if you were to get a new HEGO sensor (might as well) and install it, you'd probably notice an improvement in fuel mileage.

5-90

 

[bajacalal]

Which sensor are you talking about?

The upstream one, which is the computer's input for fuel metering or the downstream (just after the cat). Apparently the downstream serves to monitor the efficiency of the cat converter. Anyway it should be reinstalled. Weld on "bungs" thats the threaded hole into which it goes, are avaliable, http://www.summitracing.com and other stores.

OBDII era vehicles have a downstream sensor, if you have an earlier vehicle (than 95 I think) it will have only the upstream one, located at the downpipe, after the exhaust header. What year is your xj?

 

[camarorss350]

thanx guys i have a 97 xj, im not sure witch sensor it is be cause there is NO place for it to be inserte, in GUESSING its supposed to be after the cat, it dangles right near the TC, i calculated my last tank of gas and i only got 16 mpg and sometimes when i floor it, it seamms to miss realllly bad, and studder

 

[langer1]

thanx guys i have a 97 xj, im not sure witch sensor it is be cause there is NO place for it to be inserte, in GUESSING its supposed to be after the cat, it dangles right near the TC, i calculated my last tank of gas and i only got 16 mpg and sometimes when i floor it, it seamms to miss realllly bad, and studder

Sounds right, the wire for the other 02 sensor would be way to short to be way down there.
The sensor that's out would not effect you mileage though.

 

[gjxj]

It should throw a code though, so if your service light isn't on you probalby have some hack bypass circuit somewhere. You should figure out what you've got in case you ever need to go through emissions inspection. Also I'd expect most good shops will want to restore the emissions system before doing anythig else.

Have you checked that your SES light even works?

 

[camarorss350]

yea the ses light works, i still have a problem with the air bag light though. it comes on and off at random times, i even replaced the whole cluster with a different one and its fine...

 

[camarorss350]

what exaclty is a HEGO sensor, ive never heard this term before? also, i'll prob be going with a header back exhaust system soon, what does everyone think i should get? who makes headers and downpipesfor jeep 4.0's? i read that borlas good, but a little out of my price range, is there anything cheaper? also, should i go with 2 1/2" piping from the downpipe back?

 

[explorer]

HEGO - Heated Exhaust Gas Oxygen - Sensor. In my opinion the aftermarket performance headers are not worth the money. They still crack like the stock manifold, which is also a tubular header technically. No substantial performance increase, and evenwith the Borla million mile warranty, don't think its going to last near that long. You will be replacing it due to cracks. I have welded up the cracks in my original manifold two times and it needs it again now, but its more or less free other than my labor.

 

[camarorss350]

awesome, well what about the rest of the exhaust, is it even worth it to do that?