1996 6 cyl, check engine lights for a few days. I believe I get codes 51 and 21. Runs a little rough as I approach idle, but doesn't give out. Smell exhaust when I get out of the truck. Any guesses?

 

go to any of the major auto chains, they will plug their code reader in and see what it says

 

21 and 51 would be oxygen sensor codes

 

thank you for your quick reply. I have found these notes:
51 O2 detects lean mixture. Check sensor and circuit and for vacuum leaks.

21 Oxygen sensor or circuit. O2 sensor or wiring faulty.

Have any of you experience with fixing this type of thing, i.e is this a self-repair or shall I take it to the shop?

 

It is a pretty easy fix. Getting the old ones out is probably going to be the hardest part. There are 2 oxygen sensors though and with the codes you gave us it is impossible if its just 1 of them or both. Replacing both would probably be the best way to go but they are somewhat expensive. Auto part stores will usually hook a scanner up for you and can probably tell you if it is 1 or both.

 

Awsm. Thanks for your help. I am willing to give it at try, what the hey. I'll check at the store and get two and track em down in the truck.

 

oh, hmm could this also indicate a problem with a vacuum hose?

 

Oxygen sensor codes can be, but are not always related to the sensor itself.

An imbalance in vacuum/exhaust (leaks) can contribute to this.

As always, inspect wiring and connectors.

Regardless of root cause, oxygen sensors have a finite lifespan of between 100k- 150k.

 

I experienced the O2 sensor failure in my 97 XJ a few years back. In my case, it would not give an error code, but the engine would barely run. Finally I limped it in to a repair shop and they were able to read a code. I recall the O2 sensor replacement being very fast and inexpensive, and instantly solved the engine problem.

 

Thank you all for the great info. I will get and replace both the upstream and downstream... I'm over 150k miles anyway. We'll see what happens.

 

With over 150k, those oxygen sensors don't owe you anything.

Stay away from el-cheapo sensors on e-bay. Go with name brand. I like Bosch if available.

Let us know how you come out.

 

Ok, one down, one to go. Replaced the upstream sensor, and jeep starts and runs, whew. I'll wait till the end of the week to do the other, that way I have a couple of days to work with in case I screw it up. Thanks for the all the great help.

 

Ok - now both sensors replaced. Jeep runs so much better. No stuttering into a stop. Plus the smell (and taste) has gone away. A lot easier than I thought. And I figure I would know by now if I had crossed the threads...

On the other hand, while under there I noticed a nice hole in my muffler. When I turned the jeep on, and took a peek back underneath to check my work, there was water dripping out of the muffler's hole. It never ends...

 

Mine does that too. I just try not to think about it.

 

Don't sweat it, if you can wait Dynomax may have their cat back special again. After the rebate it's like $75 and 20 minutes of your time.