Running rich after O2 sensor change - Page 2 - JeepForum.com

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post #16 of 99 Old 01-07-2012, 09:55 AM
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Originally Posted by Bad_Dog View Post
It does start. After I reset the codes, the first start-up, it's fine (I'm in NY and it's been very cold the last few mornings). After the first or second startup, it would run like it's hesitating. A lot of smelly exhaust. But after it warms up, it seems to idle fine. If I start it up and try to step on the accelerator before it warms up, it sounds like it's wanting to stall - I'm guessing that it's getting way too much gas and choking.
Could you pull one of the plugs and take a look at it? Or post a pic? That will tell you for sure either way. It sounds like it may be temperature dependent. If so, bear in mind that the engine doesn't read the O2 sensor until it reaches a certain temp - I think its 165F or so. This means that if your temp sensor is going bad, then it may never even read the O2 sensor at all. Or if it does, it may be reading it all the time.
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post #17 of 99 Old 01-07-2012, 10:05 AM Thread Starter
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Quote:
Originally Posted by oldtime_ironman View Post
Could you pull one of the plugs and take a look at it? Or post a pic? That will tell you for sure either way. It sounds like it may be temperature dependent. If so, bear in mind that the engine doesn't read the O2 sensor until it reaches a certain temp - I think its 165F or so. This means that if your temp sensor is going bad, then it may never even read the O2 sensor at all. Or if it does, it may be reading it all the time.
.
Just pull any one of the spark plugs? What am I looking for?

If the PCM has the 'rich code' still stored, won't it know that it is/should be running rich already, regardless of temperature?

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post #18 of 99 Old 01-07-2012, 10:14 AM
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Originally Posted by Bad_Dog View Post
Just pull any one of the spark plugs? What am I looking for?

If the PCM has the 'rich code' still stored, won't it know that it is/should be running rich already, regardless of temperature?
Any one of the plugs should work. You're just looking for massive amounts of caked-on soot.

Far as the PCM goes, it shouldn't be storing codes if you reset it. If they came back, then either your O2 sensor/circuit is screwy, or it is indeed running rich. Checking the plugs will tell for sure if it is indeed running rich, or if there's just something weird with the O2 sensor. In other words, the computer may be reacting to a bum reading even tho everything should be fine.

One thing you can try also is to unplug and then re-plug the sensor back in a couple times. In case the connector is corroded at all.
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post #19 of 99 Old 01-07-2012, 11:49 AM Thread Starter
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I pulled one of the plugs, looks okay to me. Here are the pics...

I looked underneath while it was running and didn't see any leaks.

I put a meter on it. I got a reading on the gray and black wires. It registered between .8 and .9 volts. If you're saying that it needs to be around .4, sounds like I have a bad O2 sensor?
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post #20 of 99 Old 01-07-2012, 12:10 PM
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Originally Posted by Bad_Dog View Post
I pulled one of the plugs, looks okay to me. Here are the pics...

I looked underneath while it was running and didn't see any leaks.

I put a meter on it. I got a reading on the gray and black wires. It registered between .8 and .9 volts. If you're saying that it needs to be around .4, sounds like I have a bad O2 sensor?
Well that's just weird. Those plugs sure weren't running too rich! Those plugs sure don't look like its running too rich to me. They look somewhere in between "just fine" and "could use a tad more gas". Its possible you got a bad sensor - where did you have the meter grounded on when you tested the sensor? I'm wondering if the wiring to and from the sensor is OK

.
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post #21 of 99 Old 01-07-2012, 12:13 PM
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That plug looks OK. If you do not hear any exhaust leaks then the issue may be the O2 sensor.
What brand O2 sensor did they use?
See if the wires were cut/spliced for the O2 sensor?
If it is then it is not a direct fit O2 sensor from a reputable company like Denso but a POS chinese hunk of crap. They are about $55.00 at Advance Auto Parts.

Before you start throwing parts at this issue make sure the part you are replacing is NG. I do believe testing the voltage it sends to the brain was mentioned.

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post #22 of 99 Old 01-07-2012, 12:15 PM Thread Starter
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Originally Posted by oldtime_ironman View Post
Well that's just weird. Those plugs sure weren't running too rich! Those plugs sure don't look like its running too rich to me. They look somewhere in between "just fine" and "could use a tad more gas". Its possible you got a bad sensor - where did you have the meter grounded on when you tested the sensor? I'm wondering if the wiring to and from the sensor is OK

.
I had unplugged the sensor from the bracket and just tapped two of the four wires from from the sensor. There are a gray, black and two white wires coming from the sensor - I probed the gray and black ones.

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post #23 of 99 Old 01-07-2012, 12:16 PM
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Originally Posted by oldtime_ironman View Post
Well that's just weird. Those plugs sure weren't running too rich! Those plugs sure don't look like its running too rich to me. They look somewhere in between "just fine" and "could use a tad more gas". Its possible you got a bad sensor - where did you have the meter grounded on when you tested the sensor? I'm wondering if the wiring to and from the sensor is OK

.
What do you figure??? His mechanic installed an el cheapo O2 sensor and it is NG or he botched the splicing job? Maybe both!

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post #24 of 99 Old 01-07-2012, 12:17 PM Thread Starter
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Quote:
Originally Posted by laybackman View Post
That plug looks OK. If you do not hear any exhaust leaks then the issue may be the O2 sensor.
What brand O2 sensor did they use?
See if the wires were cut/spliced for the O2 sensor?
If it is then it is not a direct fit O2 sensor from a reputable company like Denso but a POS chinese hunk of crap. They are about $55.00 at Advance Auto Parts.

Before you start throwing parts at this issue make sure the part you are replacing is NG. I do believe testing the voltage it sends to the brain was mentioned.
The brand is Walker. I bought it from my local Napa store. Part # 250-24002.

No splicing, it was a direct plug-in. The shop did put zip ties on the excess wiring, but that's the only modification that I can detect.

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post #25 of 99 Old 01-07-2012, 01:31 PM
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Originally Posted by oldtime_ironman View Post
Could you pull one of the plugs and take a look at it? Or post a pic? That will tell you for sure either way. It sounds like it may be temperature dependent. If so, bear in mind that the engine doesn't read the O2 sensor until it reaches a certain temp - I think its 165F or so. This means that if your temp sensor is going bad, then it may never even read the O2 sensor at all. Or if it does, it may be reading it all the time.
.
Great thougt concerning an often over looked possibility.

It seems to go into closed loop mode once and run fine. The next cold start up it runs like crap UNTIL the engine goes into closed loop mode.

If the O2 sensor was NG it would start to run crappy once it goes into closed loop mode wouldn't it?

Somtin' is tell the brain to go into closed loop mode after one start cycle while the engine is supposed to be in open loop mode.
That temp sensor is looking more and more like the prime suspect all the time...from here that is!

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post #26 of 99 Old 01-07-2012, 01:34 PM Thread Starter
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Quote:
Originally Posted by oldtime_ironman View Post
Could you pull one of the plugs and take a look at it? Or post a pic? That will tell you for sure either way. It sounds like it may be temperature dependent. If so, bear in mind that the engine doesn't read the O2 sensor until it reaches a certain temp - I think its 165F or so. This means that if your temp sensor is going bad, then it may never even read the O2 sensor at all. Or if it does, it may be reading it all the time.
.
thought more about this. Originally when I put the meter on it, it was only after the engine was cold and running for about a minute. I just went back and let it run for a few minutes. The engine was around 180F when I put the meter on the sensor again. This time, I'm getting about 0.12 volts when probing the gray and black wires.

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post #27 of 99 Old 01-07-2012, 01:44 PM Thread Starter
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Originally Posted by laybackman View Post
Great thougt concerning an often over looked possibility.

It seems to go into closed loop mode once and run fine. The next cold start up it runs like crap UNTIL the engine goes into closed loop mode.

If the O2 sensor was NG it would start to run crappy once it goes into closed loop mode wouldn't it?

Somtin' is tell the brain to go into closed loop mode after one start cycle while the engine is supposed to be in open loop mode.
That temp sensor is looking more and more like the prime suspect all the time...from here that is!
If I recall correctly, the temp sending unit for the computer is at the rear, near the firewall, along the fuel rail? If so, I checked it and it's plugged in.

Is there any way to test it to see if it's any good?

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post #28 of 99 Old 01-07-2012, 02:35 PM
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Originally Posted by Bad_Dog View Post
If I recall correctly, the temp sending unit for the computer is at the rear, near the firewall, along the fuel rail? If so, I checked it and it's plugged in.

Is there any way to test it to see if it's any good?
Other way round. The sender for the computer is n the water neck. The one at the back of the head is for the gauge. If you stick it in a pot of water on the stove at 200F it should read about 185 ohms IIRC
.
Something is definitely way off about the O2 sensor tho - way way off about the O2
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post #29 of 99 Old 01-07-2012, 02:38 PM
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You mighta just got a bad O2 sensor tho.
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post #30 of 99 Old 01-07-2012, 03:08 PM Thread Starter
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Originally Posted by oldtime_ironman View Post
Other way round. The sender for the computer is n the water neck. The one at the back of the head is for the gauge. If you stick it in a pot of water on the stove at 200F it should read about 185 ohms IIRC
.
Something is definitely way off about the O2 sensor tho - way way off about the O2
What if I run the Jeep at normal temp (190F?) and then take a reading on the sensor? I'll see if it's around 185 ohms.

But so far, everything sounds like it's a bad O2 sensor. Are the voltage readings that I'm getting, are they a good indicator that it's not good?

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