jeep58

I purchased this jeep from my nephew with 153k on it. The spark plugs I do not know how long they have been in it, it is a 2004 4.0 with the " waste spark ignition" what would be a better copper spark plug champion or nkg ?

BlueRidgeMark

I think most here would recommend the NGK for the later 4.0s with the waste ignition. I doubt it makes a HUGE difference as long as you stay wiht quality plugs and don't buy the gimmicks like Spit Fire and the like.

downs

Whatever the manual or under hood sticker recommends.

jeep58

Went with the NGK copper plugs the plugs that I tool out were real worn down they were also NGK plugs, I think that they had more then 30 k on them I can fit a 60 feeler gauge with no resistance !

dave1123

I believe NGK ZFR5N (3459) plugs are recommended for waste spark 4.0s. I use them in both my 2000 WJ and XJ. Also, it's good practice to check the gap on new plugs before installing them. This goes without saying, but many times guys don't. Many brands now have cardboard or plastic sleeves on the threaded end to protect the gaps during shipping, but the last time I bought a set of Champs, one gap was crushed closed from rough handling.

jeep58

Yes those are the NGK (3459) plugs that I used. The jeep runs good as I said before the old one were really bad center electrode was totally worn away surprised jeep even ran ! Oh yes I always gap the plugs.

jeep58

Ok so today I start up jeep early in morning and get a check engine light, I pull the code it is P0135 02 bank 1 sensor 1 . Is this the oxygen sensor upstream? Did not having spark plugs changed in such a long time by the looks of the plugs that came out cause an oxygen sensor to go out? It does have 153k on it.

BlueRidgeMark

Yes, running bad spark plugs can shorten the life of the O2 sensor. Use only Mopar/NGK/NTK sensors on these things.

jeep58

I am going to do the 02 sensor this weekend, As I was driving home today the check engine light went out I checked the code it is now stored with no pending codes present. The 02 sensr still needs to be replaced? Why did it store the code and show no present codes? Thanks

Noah911

Does the oxygen sensor need replaced? Maybe...

A oxygen sensor code may have people thinking the oxygen sensor needs replacing, but that is definitely not always the case. Many many different things may result in having your PCM to throw this code.

It could be a lot of the different wires? The ones going to the sensors, the ones going to the fuel injectors, the ones going to your coil, the ones going to your spark plugs, etc...

It could be the spark plug(s), or just a bad spark being produced by something located somewhere else in the sparks path?

Maybe a problem with improper fueling from the fuel pump, the fuel pump check valve, fuel injector faults, etc...

It could be a leak in the exhaust system, or a bad catalytic converter?

It could be the oxygen sensors themselves? Or, maybe a problem with the oxygen heater circuit...

PCM... fuel injector driver?


It is best to test the oxygen sensors to see their fluctuating voltage values getting real-time results. Also, it is a really good idea to look into your Jeeps fuel trim values too.

jeep58

Thanks I brought it to mechanic first he said the one that came up to code was bad lazy sensor, he said all four should be changed. After telling me it would be 700 dollars to change them I decided to hold off. He them checked the parameters and said that they were all working. For now I add some techtron fuel cleaner and filled up the the tank. I cleared the stored code for now and I will see what happens it has 155k on the truck. Oh he said the one sensor bank 1 sensor 1 was not heating up to spec!

jeep58

One other thing this happen o2 sensor light after I changed plugs which were ngk copper but were completely worn out!

Noah911

If the code has switched over to being a stored code now, and the Jeep no longer has an active O2 sensor code happening. I would probably just put some miles on it and see how it goes.. provided it is running good and all? The old worn out spark plugs that got changed out may have very well been the whole reason for the O2 sensor code occurring back then in the first place?

(edited to add):
I wonder what would cause that one O2 sensor not to be heating up to specifications, and how he went about finding out this information?

Noah911

I learned something;

The O2 sensor code was probably something like a P0141 code. This code is specific to a failed heater element on an O2 sensor. The reason for having a P0141 O2 sensor heater element code is most likely the actual heater element of the oxygen sensor has failed. It could also be because of a fault in the heater element wires leading up to the sensor too though, but this is much less likely to be the reason.

You could test it if you wanted. It is real easy to do.. You just pull the connector off the sensor. There are two wires (probably black in color). These two wires lead up into the oxygen sensor to supply their heater elements voltage. On the sensor side of the connector you will notice two terminals associated with the heater element wires. You just take voltmeter leads to check for resistance at these two terminals. It should be very low infinite resistance as the reading on your meter when you probe the two terminals on the sensor side of the connector. If it is not? Then, the heater element has bitten the dust and has failed.

However, if you do find an infinite resistance? The wires leading up to the oxygen sensor may have a fault in them? You can test for this too. First, turn the ignition key on and start the Jeep (I do not think you really need to fully start and run the Jeep.. probably, just need to turn the ignition key into the run position is all, but I am not absolutely sure about this?). When you probe the two pins on the wiring harness side of the connector, you should see 12 VOLTS. If you do not see 12V on the meter when you are probing these two pins? Then, this means the wires leading up to the heater element of the oxygen sensor is what most likely has the fault.

Technically, an O2 sensor that is not heating up correctly does not necessarily even need fixing. It will cause a less efficiently running engine though.. or, poorer fuel economy. How is your Jeeps fuel economy?

jeep58

Thanks fuel is not that bad, The code was a PO135 bank one sensor one. He the mechanic said to run it with mid grade gas and use some techtron which I did. He said that I should change all four 02 sensor instead on just the one. Why can't I just change the one if the code comes back that I cleared, Weather right now bad can mess with checking it but I will check with meter when it is possible. Thanks again !