I have a 2000 xj. Once it get up to 200 degrees it's runs really rough sputters and misfires. Drove it the other day and couldn't get it over 30. It was sputtering bad Only cel is for a o2 sensor. I all forums I read has all different advice. I was going to get a fuel gauge and check the pressure or should I start somewhere else? Looking to narrow it down.

 

A lot of different advice because there are a lot of different valid reasons for having both, a rough running condition and an oxygen sensor code. More information would be helpful to be able and try to figure out the reason your Jeep is having issues.

What oxygen sensor code is the CEL?

Are you able to gain access to use a scanner? If so, what are the Short Term Fuel Trim (STFT) and the Long Term Fuel Trim (LTFT) values for both banks? What are the oxygen sensors voltages doing in the real-time live data stream function, for all of them - particularly the oxygen sensor(s) responsible for throwing the CEL?

The voltages for the oxygen sensors upstream on both banks is probably going to be important to know.. as well as the LTFT and STFT values for both banks, in order to be able and see what the system is doing?

Finding out if the problem exists on just one bank? Or, if it exists on both banks? This will help in being able to figure out what is the reason, and where you need to focus to go looking for the issue.

 

A misfire is one of three reasons; inadequate spark necessary for combustion, inadequate air/fuel ratio in the combustion chambers for combustion to occur, or inadequate compression needed for combustion.

Check the fueling, sparks, and the compression... What do you find out for these three things; is also another good next step to take at this point. That, plus what is the CEL, all of the fuel trim values, and the oxygen sensor voltages in real-time? This information will help.

 

I forgot what code but it was one of the upstream ones. I know it should have two upstream ones. But it's only happens after 30 min of idleing when it get up to temp

 

With the known information; If it is only just one of the upstream oxygen sensors, then it sounds like it is a problem only occurring on just one of the banks.

This makes it possible to be a fuel injector or two on that one bank? Or, maybe a spark plug or two on that one bank? Or, maybe bad compression at one or two of the cylinders on this bank? It could also be the oxygen sensor is bad, with high voltage or no voltage, and is messing things up on this bank? There will definitely be other reasons to think up too.. these are just what first comes to mind for me.

If it is truly only on one bank.. It does sound as though this information may possibly be helping to kind of rule out certain other issues that would definitely effect both of the banks globally. Such as a fuel pump failing to maintain pressure. Or, a fuel filter doing the same.. Or, some of the sensors that would cause random misfires to occur on all of the cylinders; The Cam Position Sensor, maybe the Engine Coolant Temperature (ECT) sensor, Throttle Position Sensor (TPS), etc...

There is too little information yet to be completely sure of any of all this right now.

 

Fix known problems first.

Replace the bad O2 sensor, then go from there.

Since a fuel pressure gauge can be "rented" for free (loaner program) from various auto parts stores, it sure wouldn't hurt to check that out.

 

[QUOTE=BlueRidgeMark;3587814][[color=#e74c3c]Fix known problems first.

Replace the bad O2 sensor, then go from there.]



One could do that. It may not fix it though.. if the oxygen sensor code is being set off due to a problem with something happening elsewhere? The oxygen sensor may be perfectly fine? We do not know?

Now, if the oxygen sensor were to be stuck at any one certain voltage and not fluctuating how it ussually should during normal operation, had zero voltage all of the time, or an out of specifications high voltage (greater than 0.9 - 1.2 VOLTS)... Yes. In these cases, replace it.

You have to get the code and check to see what the oxygen sensor voltages are doing in real-time in order to know.

Comparing the oxygen sensor voltages and fuel trim data between both of the banks would be a smart thing to do too. The other oxygen sensor on the other bank may not be very far behind the one that is currently throwing the code? The other one could just barely still be within specifications to not code yet.

The oxygen sensor that is throwing a code right now may also be perfectly fine. But, the code is simply because one of its wires has developed a fault to keep in mind as well. Replacing the sensor in this case would not fix it if this were the problem either.

 

I agree that replacing the Upstream O2 sensor straight up is the most sensible action, as its known to cause similar symptoms, and needs to be replaced in any event , so not just firing parts canon, (although I would make sure its wires and connectors are good 1st)

 

After changing the O2 sensor (and use NGK) pull all the plugs and look at them. Check compression.

 

The oxygen sensor simply reports the data that it gathers. For examples, if you are getting lean or rich mixture codes, you may have a faulty fuel injector, vacuum, fueling, or compression problem. Replacing the oxygen sensor will not fix this problem. You will just get the same code again. (edited in..) Unless of course the oxygen sensor itself is faulty. This would likely show up on the data scan for you to see if it were though.

Replacing the oxygen sensor without first looking into the data will result in a missed opportunity of comparing both banks to one another under the same similar circumstances. What I mean by this.. is the new oxygen sensors performance will likely be much better than the older one still on the other bank, and it will skew results for being able to see what the entire system is doing right now. The other bank could be effected by something globally right now? If you check the data it may show you the oxygen sensor over there is struggling to maintain things within Non-CEL parameters as well..

Sometimes, replacing one oxygen sensor (especially the front engine monitoring sensor) will cause the ECU to set a code for the other sensors.This is because the new sensor switching activity is much faster than that of the older aged sensors. It is probable (or possible) that on at least most semi-modern vehicles, the code will be set within 30-60 days after the first sensor replacement. In the future, this may skew the data even further for any other potential problems that may be occuring right now and are causing the issue.

 

Ok I will be replacing the o2 sensor. Just didn't think it would make it act up that bad . I never got any misfire codes or anything else. I talk to the guy who had it before me he said he replaced the cps sensor. But why does this only happen when the engine is warm . Runs perfect before hitting operating tempeture.

 

A bad O2 sensor will do a number on how your engine runs. It's a critical sensor.

But Noah is right - make sure it's bad before you replace it. I assumed that was obvious.

What I'm saying is, do NOT try to troubleshoot other problems if you already know there is a bad O2 sensor. That MIGHT be the whole problem, or it might be a CONTRIBUTOR to the problem. You can drive yourself nuts trying to troubleshoot other things if the O2 sensor is bad. It will completely confuse the picture. So, assuming you have verified that it is bad, replace it before trying to find any other problems.

 

Found another code p0325 knock sensor. Along with the o20 which is p0132

 

The oxygen sensor output helps control engine timing, combustion intervals, and the air to fuel ratio. A bad oxygen sensor can disrupt these engine functions, causing a rough or irregular running engine; poor idle, loss of power, hesitation, stalling, etc... I think because until the engine is at normal hot operating temperature, the computer utilizes a predetermined set of parameters to run the engine until it reaches a normal hot running temperature. After the engine is hot is when the computer begins to utilize the oxygen sensor data outputs to help it determine the air/fuel ratio, combustion intervals, engine timing, etc... A faulty oxygen sensor will disrupt all of the different processes. This is why it sounds as though it is likely a fault with the sensor causing the problems.

I agree with the others it sounds like possibly the oxygen sensor itself may be bad and is causing the problem. It does not have to be the reason though. It could be something else? Especially, at minimum.. check to see if the oxygen sensor wires are okay?

I prefer to test the components and see for myself exactly what is actually happening. Many people prefer to skip the test phase.

 

P0132 code is for high voltage. Voltage is inversely related to the oxygen content of the exhaust. This means the 02 sensor is showing as detecting a low oxygen content in the exhaust.

This means the sensor is showing as having detected a rich engine running condition.

Maybe the oxygen sensor itself is bad?

It could be the oxygen sensors wiring is shorted to the metal undercarriage.. after having melted or rubbed through of its protective insulation on the moving parts or hot exhaust of your Jeeps undercarriage is another likely possible reason too though..