What is interesting is that I only show the 3 sensors
And my mass aire flow rate is. 07

 

To assess the O2S performance you have to watch the signal voltages in real time, so it would be prudent to visit a good independent mechanic who is familiar with Jaguars and have him show you the signals and how to interpret them.

As far as the MAFS signal goes, a good rule of thumb is that its signal at idle, in grams-per-second, will be roughly the same as the engine displacement in liters, so for your 4.0 liter engine, we would expect your MAFS signal to be about 4 g/s, or slightly more, perhaps 5 or 6 g/s. Your scan tool appears to be measuring in pounds-per-second. 4 to 6 g/s converts to approximately 0.01 lb/s, so your reading of 0.07 seems high.

Have you cleaned your MAFS recently? You can see the intake air temperature sensor bulb, but the hot wire is up inside the recesses of the sensor housing. Flush it thoroughly with about half a can of CRC MAFS cleaner spray. You'll be able to see the gunk on the IATS bulb go away, but you won't be able to see the MAFS wire, so fill the sensor with cleaner, swirl it around, pour it out and repeat, spraying in wherever you can. Just take care not to touch the wire or bulb with the spray can straw. Allow the cleaning fluid to evaporate and reinstall the MAFS.

If you scan tool can read the engine coolant temperature, check that with the engine fully warm and report it here. Also, if it can read fuel trims, check the short-term and long-term fuel trims (STFT & LTFT) at idle, 1,500 rpm and 2,500 rpm and report them here and we'll try to help interpret them.

Cheers,

Don

 

It seems your OBD2 scanner isn't reading the car properly. I have an iPhone running the Car Scanner app and Bluetooth scanner which shows all 4 sensors in the system.
It would be good to know which OBD2 adapter you have and maybe look for a better app

 

Here are the readings from my Torque APP

RPM 1500. LFT1 & 2 4%. STF1 5% SFT2 0%. MAF .4 G/S . Coolant 184
RPM 2500 LFT1 & 2. 4%. STF 1 & 2 7% MAF and Coolant are the same above

All the O2 are showing 7.41V After looking at it it is showing 8 OT sensors but they are all the sam

 

If your fuel trims at idle are similar to the ones you posted, they all look fine.

Your coolant temperature seems low. I typically see temps in the 195-205 range with the engine fully warm and idling. Your coolant thermostat may be stuck open.

If your MAFS signal is really reading 0.4 grams-per-second at idle, it is reading very low. It should read at least 4 g/s.

Off the top of my head, in the AJ16 the upstream O2 sensors' voltage should swing high and low between just above 0 volts and just below 1 volt (typically between 0.1 volt and 0.9 volt). The downstream sensor signals should remain steady at around 0.45 volts (450 millivolts) or so, sometimes as high as 0.6 volts (600 millivolts).

Cheers,

Don

 

I changed out my MAF and it shows the same. It may be the app that is reading it wrong. I have one more and may swap it out to see if it changes. Yea I was reading the wrong voltage. I went back out and checked and it is running between .96 and 1. Thanks for your help and will keep you posted on the changes

 

So I changed it to another MAF and it shows the same at .04 so I am thinking the tool is off one decimal. I went ahead and looked for the MAF cleaner and in Albuquerque, it is nowhere to be found. I guess the tweakers have something new they are using. I ordered some from Amazon. I noticed that my LTFT stayed at .78 for a while until the car got hot and then it jumped to 1.56. So I guess everything is running fine. It did heat up to 200. I also noticed the downstream did not stay steady, or the upstream for that matter, while on the highway. They fluctuated all over the place. I am going to go ahead and take it to a Foreign car mechanic. Not too many in town to trust except for the Jag dealership but don't want to pay the "Man".

 

The upstream O2S signals should fluctuate up and down frequently. The downstream O2S signals should be steady. If the downstream signals fluctuate, the sensors may be failing, but more likely your catalytic converters are no longer working properly. Have you had P0420 or P0430 diagnostic trouble codes (catalyst efficiency below threshold)?

Your fuel trims look good. Anything below +5/-5 is fine.

CRC Mass Air Flow Cleaner spray is available at most auto parts stores in our area, and also at Walmart. It comes in a spray can with a gray and white label.

Cheers,

Don

 

The whole city is out. Could be COVID. I replaced the CC about 10 years ago and have about 90k on them and it passed emissions about two months ago so it is probably the sensors. Any recommendations

 

No offense intended, but "it is probably the sensors" is not a diagnosis. And given that your fuel trims are well within the +10/-10 range, you haven't demonstrated any evidence that points to the oxygen sensors.

If you're rolling in money and would rather throw money at your car and possibly make little or no difference in its performance, the original equipment oxygen sensors are made by NTK and are available from Rock Auto for about $65.00 each plus tax and shipping.

Are any diagnostic trouble codes stored in your ECM?

Cheers,

Don

 

OBD on x300 never shows correct MAF readings, anything from 0.02 to 0.07 is fine as far as no other errors and if car runs ok. Cleaning it without disassembling it is a complete waste of time/chemicals and money, which becomes very clear when you do take one apart. To do it, you'll need to drill out the rivets which you can then replace with screws.
To properly test oxygen sensors you'd need an oscilloscope or an analogue multimeter. OBD is too slow and inaccurate to test its performance. What it will tell you is whether it changes from open to closed loop mode and how quickly that happens(it should within a 100 meters in the summer), whether the heater works(it would give an error if it doesn't) and should give you a rough idea on whether it cycles between 5V and 0V. With the old sensor the cycling is generally much slower, with the new much quicker, which again can only really be shown when you use an old analogue multimeter or an oscilloscope.

 

Just reread the thread.

CDMA, do you have any problems? I feel like we're running around in circles looking for a problem to solve here.

(MAF on AJ16 is indeed a decimal off, so that's normal)

 

So I took my car to a European mechanic. Supposed to be one of the best in town. After dropping off my car I tell him that I have been having MPG issues. After a while he calls me and says that there has to be something wrong with my MAF because he was also reading .04. I ask him are you sure that it is not a decimal place issue because I have two other MAF's that show the same thing. He says that he does not think so since he has been doing this for a while. I am sure he will figure it out but other than a bad MAF is there anything else it could be? I mean all the MAF's show the exact same reading.

 

I think we've discussed this already, but when I notice a drop in fuel economy, the first things I suspect are a stuck-open coolant thermostat and/or a failing engine coolant temperature sensor (ECTS). One or both of these issues can prompt the engine control module (ECM) to continue applying cold-start fuel enrichment even after the engine is warm. Your fuel trims indicate that the ECM is adding fuel, which typically means unmetered air is entering the intake after the MAFS. So it's possible you have multiple issues that are causing your lowered fuel economy.

We'll be curious to hear if the mechanic figures anything out.

Cheers,

Don

 

It won’t be the maf as they rarely fail ,I’d say o2 sensors as my economy has gone to over 20mpg on a run with new ones fitted

 

It's 100% not the MAF, at least not because of the decimal reading on the MAF.

It is normal. All of our cars read the MAF that way.

Cross the MAF off the list.

If your LTFT is at 2.4%, your MPG is about normal. When that rises, come back and report. Right now you might be chasing a problem that doesn't really exist.

 

So .4 is normal which tells me I am not sure if the mechanic knows what they are talking about. I brought him a new thermostat and sensor and he was still reading the same thing. This is the scary part...he is telling me that it is the ECU which I find it is hard to believe since I have no bad codes. I guess I need to pick up my car and stay with what you guys are telling me. He is supposed to be the best European mechanic in town. Saw everything at his shop except for Jags.

 

He’s just confused. He’s right, the number is off, but since he hasn’t worked on your car/engine before, he’s not aware of the OBD2 report/mixup. It’s a normal reading unfortunately. Cross of off the list.