MAF sensor and O2 sensor bad?

[Michael Gain]

Ordered a new vacuum line and air sensor. When cleaned with MAF cleaner, dirty liquid poured out (probably oil or the CRC cleaner. I'm also eying the temp sensor on the front of the intake. I did not pull it, but will this weekend to assess.

As far as fuel demanded vs actual:

Idle:

Light throttle:

Cruising:

The maf and fuel rail pressure fluctuated. When coasting, bank 1 MAF still goes to zero while bank 2 stays positively in the thousands. Fuel rail pressure never makes it to 19800, but gets close.

Looks like I am going to give the bank 1 MAF harness connector a better look.

I have also toyed with the idea of adding additional grounding straps to increase the efficiency of the system. I'm not sure how much that would **** the truck off though.

 

[jlglr4]

On fuel pressure, I think that’s about what I see in my truck - I don’t know if it’s correct or not, but it’s really quite a small percentage of difference between demanded and actual pressure.

It’s really strange that the one MAP goes to zero when coasting. I understand there could be a bad wire somewhere, but not sure why it does it when coasting. You replaced both sensors, right? I guess you could swap them just to make certain you didn’t get another bad one.

Looking at the wiring diagram I have (which is from 2011 - but I’m guessing it’s the same), the MAFs seem to be harnessed together into a single plug, and are grounded through the ECM. No idea what additional grounding would do. Seems the most likely point for failure would be the harness connector right at the MAF sensor.

When I go out for a drive later today, i’ll measure my charge air temp voltage for comparison. I believe the sensor you cleaned at the back is the MAPT (MAP + Temp). There is apparently another MAP (no T) near the throttle body.

 

[jlglr4]

Just to follow up, my charge air voltage looked about the same as yours - about 1.5 at idle and up to around 1.8 while driving.

 

[Michael Gain]

I really appreciate you helping me go back and forth on this thing. Yes, both MAF sensors replaced and still no codes. I will check the fuel trims again today as well. I may just have to bite the bullet and install these damn exhaust manifold gaskets. We talked about it before, but I bet the exhaust manifold o2 sensor is adjusting for the exhaust leak. Not to mention, it is an annoying tapping noise lol.

The land rover setup is overkill in my opinion. I remember forced induction forums years ago and we would talk about benefits of speed density over MAF sensors. The land rover has both: two map sensors, two air intake temperature sensors, and two MAF sensors.

The truck definitely keeps me busy.

 

[Michael Gain]

The mystery deepens. I had a little time this morning waiting on someone and went down the entire list of live value options that I thought would apply to my situation. All of these values are at idle.

While none of the individual cylinders show misfires, the combined values show this:

And in this one it shows that the ECM is cutting fuel to bank 1:

I am getting > +10% in both banks for LTFTs, but the secondary o2 sensors are trying to reduce fuel (marginally):

Even more strange is the second o2 sensor voltage. Bank 2 stays constant, while bank 1 fluctuates:

 

[Michael Gain]

Reached my max photos above...

Finally, and I am not sure what it means, the throttle position sensors (I guess we have two?) Are showing two, different voltages. I'm guessing this may cause conflicting information to the ECM:

 

[jlglr4]

The fluctuation in the post-cat o2 sensor doesn’t seem right. Not sure if that’s a sign of cat damage, or maybe a bad sensor. Hard to believe the cat would be bad already. Wondering if the exhaust manifold leak is on the same side as your wonky post-cat o2 sensor? If that’s causing it, I just don’t know why you wouldn’t also see that in the pre-cat o2 sensor.

I just don’t know much about how the engine counts misfires, or whether any of those other related parameters are significant or not. You don’t seem to have any related fault codes, so it must still be within some kind of range of tolerance.

There are indeed two position sensors in the throttle body (I checked the wiring diagram), but I don’t know how they work together. Maybe it improves accuracy. Do the voltages on both change when you hit the gas?

I’ll try to run some of these values tomorrow on my car just for reference. At least we can see if the throttle position sensors read the same. Not sure we’ll get much insight into the other numbers.

 

[DaytonaRS7]

non-helpful comment....

i wish you luck. you've dug into the depth of actually trying to understand LR ECU communication. that's a deep rabbit hole.

I am curious to the solution of this though.

 

[Michael Gain]

The fluctuation in the post-cat o2 sensor doesn’t seem right. Not sure if that’s a sign of cat damage, or maybe a bad sensor. Hard to believe the cat would be bad already. Wondering if the exhaust manifold leak is on the same side as your wonky post-cat o2 sensor? If that’s causing it, I just don’t know why you wouldn’t also see that in the pre-cat o2 sensor.

I just don’t know much about how the engine counts misfires, or whether any of those other related parameters are significant or not. You don’t seem to have any related fault codes, so it must still be within some kind of range of tolerance.

There are indeed two position sensors in the throttle body (I checked the wiring diagram), but I don’t know how they work together. Maybe it improves accuracy. Do the voltages on both change when you hit the gas?

I’ll try to run some of these values tomorrow on my car just for reference. At least we can see if the throttle position sensors read the same. Not sure we’ll get much insight into the other numbers.

As always, thank you for the comparative analysis! Unless the GAP selections are labeled differently, I think sensor 2 is the pre cat sensor. The lamda sensor is on the exhaust manifold (what I call sensor 1). As I keep playing with the truck, I change my mind on what things mean. Technically, the lamda and pre cat sensors should inform STFTs. Which sensor is assigned to which live value? I'm not sure.

I'll just unplug it and see which sensors voltage goes to zero lol.

You're right. The misfire data is there. I am just not sure what it means. I will check the throttle voltage for changes this weekend.

I owe the group better data points as well. I will measure fuel trims again at idle, 1500rpm and 2500rpm--hot and cold.

My symptoms as definitely temperature related. The truck performed flawlessly on the drive to work (48F ambient) UNTIL the engine warmed up. Once I hit operating temperature it started to bog down again. It did take about 15 minutes of driving to reach operating temperature.

I am not sure if it is overcooling, but the fan and thermostat were already replaced...

 

[Michael Gain]

non-helpful comment....

i wish you luck. you've dug into the depth of actually trying to understand LR ECU communication. that's a deep rabbit hole.

I am curious to the solution of this though.

Haha all comments are helpful. At least people are reading my struggle and may have an epiphany to help the group.