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Discussion Starter · #1 ·
I have been having some random hesitation which only seems to happen when the car is at normal operating temp. Usually I will drive for a bit then stop somewhere and when i start up and start to go it bogs down, then when I stop at lights it sputters for a sec. I had melted a hole through one of my exhaust valves in cylinder 3 so when i was driving it, it was running hella rich and just dumping unburned fuel into the exhaust. So my question is could this have clogged up my O2 sensor causeing the hesitation? My logic behind this is that when the engine is cool it runs a tad richer until it gets to normal operating temp, then relies on the O2 sensor to make the appropriate air/fuel mixture. I am not throwing any codes either. Does this seem feasible?
 

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Yes, a dirty oxygen sensor could cause drivability problems. If the readings are weak, but still present, you won't throw a CEL but the car could drive like crap.

I accidentally damaged the wires on mine. It was not always making a full connection, so sometimes it'd run great, and other times it would sputter and struggle. A simple replacement sensor took care of it immediately.
 

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once you replace that O2 sensor, won't you have the same problem a little bit down the line? Since the O2 sensor will get dirty once again? So basically you'll be in the same boat. Wouldn't the best thing to do is fix whatever problem ( in his case, dumping unburned fuel into the exhaust ) AND THEN replace the O2 sensor? Just a thought.
 

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There's one before the cat and one after the cat. Isn't one ( I can never remember which one ) more useful than the other? So technically you only need that one, and not really the other?

(Same as above. Not trying to thread jack.)
 

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Discussion Starter · #7 ·
I DID fix the valve, but the problem is from when I drove my car to the shop on 3 cylinders some 15-20 miles away. So I won't have the same problem down the road, unless I melt another valve, which I don't plan on doing.

Yes there are two sensors, the second is only there for emissions reasons which I bypassed with an O2 sensor simulator and is not in the cat. The front O2 sensor handles the a/f mixture and I found a Denso replacement for $95 shipped.
 

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You would need to find if the fouled o2 sensor is the upstream or downstream. If you can, or have a repair shop do it, run a diagnostic for history codes, this may assist you in repairs. If you have not replaced your o2 sensors in a while, you should do both and get it over with. Also, Foulage is usually from excess carbon and/or running excessivley rich. When is the last time your vehicle was fully serviced? (i.e. Tune up, cap, rotor, plugs, wires, valve adjutstment, fuel filter etc)
 

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When cold, the engine is running in open loop, not feeding off the O2 sensor. It has to run a tad richer to get the engine into operating temps. Its what the ECU has set for cold startups.

It is possible that it damaged the O2 sensor in the process of dumping all that fuel into the exhaust stream. May have damaged the cat too but then again you woulnd't be able to know since you don't have the secondary O2 sensor.

Check out this thread for a cheap O2 replacement if you want to try and see if it works.
 

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Discussion Starter · #10 ·
Nope it's a 97 OBDII however I put a O2 sensor simulator which sends a dummy signal to the ecu to trick the ecu into thinking the second sensor is there. I removed the second sensor so I am only using the upstream sensor. That is the only I am replacing. It has 85K on the motor so I am replacing it anyway as maintenace now.
 

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UCBeef on Feb/16/06 said:
Nope it's a 97 OBDII however I put a O2 sensor simulator which sends a dummy signal to the ecu to trick the ecu into thinking the second sensor is there. I removed the second sensor so I am only using the upstream sensor. That is the only I am replacing. It has 85K on the motor so I am replacing it anyway as maintenace now.


I had an o2 simulator for my s-10, and from experience be weary they don't always work. Especially if it is exposed to too much heat.

Quote: sak on Feb/16/06 When cold, the engine is running in open loop, not feeding off the O2 sensor. It has to run a tad richer to get the engine into operating temps. Its what the ECU has set for cold startups.

It is possible that it damaged the O2 sensor in the process of dumping all that fuel into the exhaust stream. May have damaged the cat too but then again you woulnd't be able to know since you don't have the secondary O2 sensor.

Check out this thread for a cheap O2 replacement if you want to try and see if it works.
It's possible that it could happen, but then you would have to see if you have an IACV or PCV problem.
 

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UCBeef on Feb/16/06 said:
Nope it's a 97 OBDII however I put a O2 sensor simulator which sends a dummy signal to the ecu to trick the ecu into thinking the second sensor is there. I removed the second sensor so I am only using the upstream sensor. That is the only I am replacing. It has 85K on the motor so I am replacing it anyway as maintenace now.

whoa sorry bout that, at first glance i thought it said 94 gsr., but anyways good luck

btw. i deleted my previous post since it was just clutter anyways :D
 

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Discussion Starter · #13 ·
I broke the PCV valve while removing the head to replace the valve so it has been replaced since. I also removed it two weeks ago to check if i could only blow one way thorugh it.

The simulator just sends a singal to tell the ecu that the cat is working for emissions purposes. It shouldn't affect the way the car runs, keyword is shouldn't. I've had it on there for almost a year now.
 

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MarkAnthony on Feb/16/06 said:
It's possible that it could happen, but then you would have to see if you have an IACV or PCV problem.
All the more better to really see if its something else besides the O2 sensor.
 

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sak on Feb/16/06 said:
Quote: MarkAnthony on Feb/16/06It's possible that it could happen, but then you would have to see if you have an IACV or PCV problem.

All the more better to really see if its something else besides the O2 sensor.
That is so very true. If there is one thing as a tech I have learned is that problem A will have multiple variables to the solution.
 

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Discussion Starter · #16 ·
Regardless of whether it turns out to be the O2 sensor or not I have already ordered the new one and it is something that should be replaced at 100k anyway. So if it doesn't take care of the problem I will move on down the list. I did replace the PCV and the it idle's fine. But I havn't run any diagnostics on the IACV yet so who knows.

The main reason for this post was to see if my logic holds true for this scenario.
 
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