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FC · 07-25-2010, 08:47 PM

Not a lot of awesome content, but dammit not nearly enough of us get dirty with the car, so I figured I'd post re: my bit of weekend car wrenching.

What a PITA.

I felt pretty lucky because it was the easiest to get to out of the 4. However, when it became apparent that the threads were virtually fused, it was probably the worst sensor to get enough leverage on to break the threads loose.

In the end, the special O2 tool was useless since it was vary tall, and way too loose. I took a Dremel with the fiberglass-reinforced cutter and cut everything above the hex (22mm). I then was able to fit a standard 6-point socket but I still could not get enough leverage with a standerd 1/2" ratchet. I went out and bought this.

Not only did it let me get the handle out from the innards of the Jeep but it was longer too. I stuck a tube for added leverage and finally broke it loose. Brutal experience considering the heat and a very bad wrist (weird soccer incident).

Handy JGC (WJ) website. Note the O2 sens I replaced was 2/2 (right back, downstream) on the 4.7L.

Anyhow, it could be just me but this is what I noticed after a brief drive (enough to just get the engine to temperature):

1. The car felt noticeably faster. I've been driving it daily since they tore up the road to my work and it was a pretty immediate sensation of improved response and power.

2. The jeep has been averaging a dysmal 12.X mpg recently without aggressive driving. Even with a decent amount of hwy mixed in I don't crack 15mpg. This compares poorly with the 14.7mpg around town with pretty aggressive driving when I got it, and 17+mpg with hwy driving thrown in. I reset the mpg meter and in the 2-3 mile drive with hills, stops and goes and a bit of punching, the car read 15.8mpg when I got back home.

3. This is the weird one. I am 99.9% certain I installed everything correctly (not much to it), yet the exhaust sounds different. There is a bit of muscle car-like burble with brief taps of the gas at crawl speeds (I noticed when trying to get the jeep back on the rhino ramps). If I rev it, the engine sounds smooth and the exhaust normal, but the tone has definitely changed a bit. This is not something I remembered from a year ago. A simple hover near the sensor doesn't reveal the tale tale sound of an exhaust leak to my ear (engine idling).

Now, to be fair, the CEL did come up within a few months of ownership but then went away. Then again recently and it went away again. Several weeks ago it came on for good.

Could it be that even though the sensor was well enough to make the OBD shut the light off it still wasn't working 100%? In other words, does a O2 sensor's performance deteriorate until it is so bad that the light comes on, or is it more of a yes/no fault where if it is not perfect the light gets triggered?

07-25-2010, 08:47 PM	#1
FC Solving problems Join Date: Oct 2003 Carmudgeonly Ride: M5 / 718 GTS / Cooper S / GTI / LR4 Location: Metro Boston Posts: 25,274	Replacing O2 Sensor on JGC Not a lot of awesome content, but dammit not nearly enough of us get dirty with the car, so I figured I'd post re: my bit of weekend car wrenching. What a PITA. I felt pretty lucky because it was the easiest to get to out of the 4. However, when it became apparent that the threads were virtually fused, it was probably the worst sensor to get enough leverage on to break the threads loose. In the end, the special O2 tool was useless since it was vary tall, and way too loose. I took a Dremel with the fiberglass-reinforced cutter and cut everything above the hex (22mm). I then was able to fit a standard 6-point socket but I still could not get enough leverage with a standerd 1/2" ratchet. I went out and bought this. Not only did it let me get the handle out from the innards of the Jeep but it was longer too. I stuck a tube for added leverage and finally broke it loose. Brutal experience considering the heat and a very bad wrist (weird soccer incident). Handy JGC (WJ) website. Note the O2 sens I replaced was 2/2 (right back, downstream) on the 4.7L. Anyhow, it could be just me but this is what I noticed after a brief drive (enough to just get the engine to temperature): 1. The car felt noticeably faster. I've been driving it daily since they tore up the road to my work and it was a pretty immediate sensation of improved response and power. 2. The jeep has been averaging a dysmal 12.X mpg recently without aggressive driving. Even with a decent amount of hwy mixed in I don't crack 15mpg. This compares poorly with the 14.7mpg around town with pretty aggressive driving when I got it, and 17+mpg with hwy driving thrown in. I reset the mpg meter and in the 2-3 mile drive with hills, stops and goes and a bit of punching, the car read 15.8mpg when I got back home. 3. This is the weird one. I am 99.9% certain I installed everything correctly (not much to it), yet the exhaust sounds different. There is a bit of muscle car-like burble with brief taps of the gas at crawl speeds (I noticed when trying to get the jeep back on the rhino ramps). If I rev it, the engine sounds smooth and the exhaust normal, but the tone has definitely changed a bit. This is not something I remembered from a year ago. A simple hover near the sensor doesn't reveal the tale tale sound of an exhaust leak to my ear (engine idling). Now, to be fair, the CEL did come up within a few months of ownership but then went away. Then again recently and it went away again. Several weeks ago it came on for good. Could it be that even though the sensor was well enough to make the OBD shut the light off it still wasn't working 100%? In other words, does a O2 sensor's performance deteriorate until it is so bad that the light comes on, or is it more of a yes/no fault where if it is not perfect the light gets triggered? Last edited by FC; 07-26-2010 at 03:21 PM.