I wonder what made the mechanic believe it was the heads?

 

I have some more thoughts;

I believe, or want to think I might have an idea on what may be the cause of your issue. I'm not sure 100% exactly, but..

I really think you have a problem at the oxygen sensor(s) for bank #1. Either the sensor(s) themselves, or the wiring leading from the O2 sensor(s) to the ECU-PCM. There is a slight possibility it could be related to a fault with the PCM itself too.. with how the PCM drives the injectors, or utilizes 02 sensor data, but I don't think so.

I am going to recommend for you to use your OBDII live data streaming function to look at the O2 sensor voltages. Just some background information on the O2 sensors first though:

The O2 sensors are heated narrow band sensors that generate a small voltage based on the oxygen gradient (atmospheric oxygen vs exhaust oxygen). When exhaust oxygen levels drop this oxygen gradient increases, and the voltage increases at the O2 sensors. Conversely, when the exhaust oxygen levels increase this oxygen gradient decreases, and the voltage at the O2 sensors decreases.

A high voltage reading at the O2 sensor is too little oxygen in the exhaust, so too much fuel, and the injector pulse gets shortened to compensate for having sensed a rich running condition (in the exhaust pathway). This is a representation of what you have happeneing on your bank #1.

I would think if your Jeep had a short or open in the wiring leading from the bank #1 O2 sensor(s) to/from the PCM, it would throw an O2 sensor fault code. It doesn't always do that though. It is possible for you to have a short in the signal wire of the main wiring harness going from the PCM to the O2 sensors for example, and maybe not get an O2 sensor trouble code. However, it is likely that if you have an 'operational' dysfunction of either of your bank #1 O2 sensor(s), you will ussually not get a trouble code... Also, a lot of people will tell you the rear O2 sensor does not do anything besides monitor the exhaust after the cat, and that the rear O2 sensor does not really effect a vehicles running conditions.. This is simply not true. The rear O2 sensor does not have as great of an overall impact on the running conditions of a vehicle, but it is certainly involved. Ultimately, the forward O2 sensor does rely on the rear O2 sensors information in order to function correctly...

I would run the live data streaming function with your scanner to see the O2 sensor(s) voltages in real-time. The O2 sensor voltage readings correlate with how the PCM increases or decreases the injector pulse widths.. It does this to compensate 'seeing' a possible rich/lean running condition by reading the oxygen content in the exhaust via the oxygen sensors.

The range of the signal should be from 0 volts to 1.0 volts. 0.45 volts represents a stoichiometric air/fuel mixture by way of the oxygen sensor voltage readings. If you are seeing 0.45Volts they are perfect. That will never happen seeing these sensors maintained always at their ideal...

With steady state operation (idle or steady cruise) you will typically be seeing the front O2 sensor switch between about .2 and .8 volts and the rear O2 will be steady somewhere between .35 and .65 volts.

During heavy acceleration, on to a freeway for example, you should see both oxygen sensors go up to about .9 volts and stay there through out the acceleration. If they don't go above .8 volts under heavy acceleration, then they should be replaced. Under heavy acceleration, the voltage should not be decreasing any..

On deceleration the PCM cuts fuel by turning off the injectors until the engine gets down to idle speed rpms. You should see both O2 sensors drop to 0 volts during deceleration. If they do not go below .2 volts you would probably need to replace the sensor(s)..

Remember, a high voltage at an O2 sensor means the ECU-PCM sees this as having too rich of a running condition in the combustion chambers, and compensates for this by trying to lean it out by shortening the injector pulse width.. Thereby decreasing the amount of fuel being delivered. In your case, by seeing the very high negative fuel trim values on bank #1, the PCM is drastically limiting its fuel supply!

When you are checking to see the O2 sensor voltages.. You may see bank #1 O2 sensor voltages sitting high, say maybe at a constant 0.8 - 1Volts. Or, you may find a reading even that is even further abnormally out, say at a constant 1.5Volts etc... Since the PCM relies on using this voltage to trim the fueling, it has no choice but to extremely limit the supply of fuel based on those high voltage readings. It may be doing this because of having an improperly operating oxygen sensor(s).

This is what I would recommend doing, and this is where I would recommend focusing attention at for right now. The sensors...

There are other things to consider, but since your Jeep has such extreme left values of STFT and LTFT only on the bank #1... It makes me think an associated sensor on bank #1 is the reason.

One other thing to do right now is to take a look at your spark plugs. The forward three cylinders of the engine is the #1 bank. The rearward three cylinders are bank #2. If there really is not a true rich running condition on your #1 bank, the plugs here should show as very lean.. since per fuel trim value readings, it is showing you that the PCM is limiting the fuel going to this bank in a drastic way (-32.8%). Compare bank #1 & #2 spark plugs, and maybe post a picture or two of them...

It could be the injector(s) stuck open pouring fuel into this bank when they are pressurized. It is a possibility. You could swap them around changing bank #1 injectors out for bank #2 injectors. If one or more of bank #1 injectors is stuck open or leaking badly, the fuel trim values will show it... once a little running time has gone by after you do the swap. This type of injector(s) problem having major leaking, it should show up when doing a fuel pressure test with a guage on the fuel rail. (if done correctly). You said you tested the fuel pressure already though, right?

It is good you already did a compression test of the cylinders. If you hadn't obtained normal compression readings when you did this, it could of been the reason - as excess hydrocarbons would then possibly be able to make there way into the exhaust, to be picked up by the oxygen sensors etc... But, this scenario honestly does not fit the circumstances we are seeing with the fuel trim data.

Faulty O2 sensor(s) on bank #1.
Faulty wiring of O2 sensor(s).
Faulty O2 sensor connector(s).
Faulty O2 sensor wiring in the main harness.
Faulty pin(s) on the PCM making the connection to the O2 sensor signal, or other wiring...

Faulty operational condition of the injector(s) on bank #1. Possibly too much fuel pressure being built-up causing injector(s) to over spray, or excessively leak. Although, this is not as likely... It could be injector(s) on bank #1 are sticking open? Although, again, this type of injector fueling issue, it should have presented itself with fuel gauge testing at the fuel rail.

 

Thanks for taking the time to give me your info and thoughts. I will run these tests and post pics of the spark plugs. I have been really thinking it's gotta be electrical for a few weeks now. I'm going to start by checking the voltage at the O2 sensors to see if the levels are changing like you say if they are higher or lower both because I can put my OBD2 on Livestream and I should be able to you know see all of this while driving safely and all that so I will get back to you with some results here shortly just give me about a day or two I appreciate it thanks again man

 

I had the inline-6 in mind. The 4.7L is a V

Hopefully, it is something that can be easily fixed?

 

ramoriginall, 10-04-2019 05:04 PM
Change oil and filter today and i just let it idle by the time that i got back my car was almost on red was overheating now



This may be a seperate issue presenting itself.. or, it sounds as though you have actually been dealing with several compounding issues at once? You had a faulty CPS changed out.. It improved performance some, and you now have better RPM shifting characteristics. You had three leaky injectors replaced from out of your good bank #2 (as was evidenced by the three blackened spark plugs in those same three cylinders that the injectors came out of). This means you were, or are also dealing with fouled plugs. Now, you have an overheating issue to deal with as well...

I would look at the overheating as being a seperate issue right now. Is your radiator fan coming on when it needs to? Is your thermostat opening when it should?

Of course, there is bank #1 with both of its fuel trims being greatly skewed to the negative. Fuel trims are all based on what the oxygen sensor is telling the computer. The computer wants to keep and maintain the O2 sensor as close to 0.45Volts as possible. It constantly adds and subtracts, trimming the fuel to try and make that happen. The P0172 code gets thrown after a set limit has been reached in the allowed acceptable trim value.

It does not make any sense why your bank #1 STFT and LTFT do not change any at all on your live data stream? These values should be constantly fluctuating all of the time (especially the STFT). Not the stationary number values being stuck at 32.8% like you are seeing on your scanner.

Your bank #1 trim values tells you that the PCM is interpreting data as having a rich running condition. You can challenge this: Use the live data streaming function. Start looking at the fuel trims after the Jeep gets up to its normal operating temperature (watch that it doesn't overheat). You can create a lean running condition by unplugging a vacuum line. Disconnect a vacuum line to see what happens with the fuel trims. If bank #1 STFT does not change to a more positive value after you disconnect the vacuum line, then you know there is a problem in the feedback loop mechanism on bank #1. The feedback loop is the oxygen sensor. Unplugging the vacuum line will introduce more oxygen into the exhaust pathway. This decreases the oxygen gradient. The O2 sensor is supposed to pick up this decreased oxygen gradient, and correspondingly decrease its voltage. The O2 sensor relays this new data (the decrease in its voltage) to the PCM. The PCM will add more fuel to match the increased oxygen being sensed in the exhaust. A more positive STFT would immediately result.

Utilize the live data streaming function. Set it up so you can see both - the fuel trims and the corresponding oxygen sensor voltages. Disconnect a vacuum line to initiate, and force a change on the system. You should see the STFT values immediately change to become a more positive value. After disconnecting the vacuum line, you should also see the O2 sensor voltages immediately decrease to a lesser voltage at the same time as the fuel trims become more positive.