**Correction** Sorry, It was really late when I posted #16. I thought that your last snapshot was back at idle, but was at 3K.
Simple picture from the snapshots
Stft-
idle - slightly rich within tolerances
1600 - goes lean - sort of high side of tolerances
2400 - goes to rich side - well within tolerances
3000 - stays well within tolerances

Ltft-
All RPM - Rich - Off the charts rich

It doesn't seem to be vac leak, as trims would constantly clime or drop thru RPM change, not only at 1600.
Also the LTFT are doing everything they can to maintain close to 0 by trimming down.
O2 sensor voltages might tell us more. Especially at 1600.
All your shots do not point to vac leak, intake, as your running rich, not lean which is caused by unmetered air.
It will probably point to- O2 sensors, leaking fuel pressure regulator diaphragm, faulty evaporative emissions components, leaking injectors, MAF sensor problems, high fuel pressure,or coolant temp sensor problems. You most likely will not be pulling the intake.
Let's start at O2 sensor readings and go from there. Some sensor has a dead spot at 1600.

 

Hi Mark,

That is so helpful. Thank you. Yes I don't want to go pulling apart the manifold if I don't need to.

So do my screenshots look rich on both banks? Or just one bank?

I have already replaced various things in order to solve this problem, coolant temp sensor and thermostat housing including thermostat etc. One thing I have found is that the problem goes away after I clean the MAF sensor but simply comes back in about 4 or 5 days later. I did open a forum topic a while ago on my MAF readings as I was wondering if my MAF is causing this issue as each time I clean it then the problem goes away for a while.

I've done a video of the O2 voltage readings at certain RPM which I will upload once I've got it off my phone.

Thanks again for all the help.

Cheers,

Chris

 

Replacing the 02 sensors was a lot easier job, than the internal intake manifold gaskets.

Did all four of mine chasing the vacuum leak, until finally doing them.

Finally keeping the check engine light from coming on

Hope the 02 sensors solve your issue, the manifold job isn't all that bad if necessary.

 

Cheers Wingrider. I've had the throttle body, EGR, fuel rails etc off as part of the failed fuel injectors and thermostat housing replacement so I think the manifold job would be ok to do but I just want to avoid it if I can.

Thanks,

Chris

 

AH, more of the past comes out now. What was done with the TB, EGR, and injectors? Also we should be able to rule out temp sensor as it was replaced. After confirming O2 sensors, we can look at the MAF readings before and after cleaning., as it changes things after cleaning. I wonder what the trims are after cleaning the MAF? Have you cleared ALL the codes? Wonder if the MAF has a dead spot @1600?

 

Hi Mark,

I've had this vibration issue for a long time now and just haven't been able to get to the bottom of the cause.

I had a minor coolant leak which turned into a major leak and I thought the problem might be related to the coolant sensor due to the leak. The leak was because of a crack in thermostat housing so I replaced the whole housing including the coolant temp sensor and the thermostat. I replaced the water pump at the same time as it had not been done before and was worth doing whilst I was in that area of the car. I had to remove the throttle body and EGR valve to replace the thermostat housing as they have to be removed on the NA version. That did not fix the vibration at the revs.

I've had two failed fuel injectors (both went open circuit) on bank 1 (they failed a different times) so they have been replaced as well. I have also changed the spark plugs, oil and filters and the problem still remained.

So I then cleaned the throttle body and the problem was still present.

I cleaned the MAF sensor and the problem went away for about a week and the car drove great. After that week the problem returned.

I asked the forum about what the correct MAF readings should be as I am suspicious that this problem is being caused by the MAF.

I cleaned the MAF again and the electrical connector and the problem once again seemed to go away for a while.

Do you know what the MAF readings should be at certain RPM when stationary? If I know what they should be then I can test and see if there is something not right with those readings.

I'll upload the video later today of the O2 voltage readings.

Thanks,

Chris

 

Hi Mark,

Here is a video of my O2 voltage readings together with RPM and fuel trims at various RPMs. The car currently has no fault codes registered and none pending either.


Thanks,

Chris

 

Anyone else see strange things with the O2 sensors? His stft are up and down at stable RPM. While his LTFT is buried rich.

 

If I remember correctly forum members had me check O2 sensor current @ ma vs voltage. Should be steady at about 0.02 or 0.03. Also read thru
https://www.jaguarforums.com/forum/x...74-sv8-177741/
This many help you see how we came to the solution. O2 sensor ma is discussed #32. But both banks reading LTFT really rich has me confused, as both O2 sensors would have to be reading bad. You also may want to read MAF numbers as this would affect both banks, and improves after cleaning. If you MAF is incorrectly reporting, then the ECU would be compensating for incorrect values.

 

Thanks Mark. Yes this is why I am so confused. I just can't seem to get to the bottom of the problem. But I do know that cleaning the MAF helps for a while. I will get MAF readings whilst the problem is present and then try to clean the MAF again and see what the readings then are afterwards.

 

Hi Mark,

Unfortunately I have been a bit busy with work to look further into this problem. I have now obtained the MAF readings which are in the video below.

I took the readings with the engine at full temperature and whilst stationary. I have taken the readings at idle and then had to rev a bit to get to the right RPM where the problem is most prevalent . I then towards the end rev the car to 2000 RPM.

I've just got to find the time to now clean the MAF and see if the figures change afterwards.

Can you see anything wrong with the MAF readings before I clean it?


Thanks,

Chris

 

Don't have time tonight to research, but will tomorrow night

 

Thanks Mark. Really appreciate the help.

 

I now have just had a fault code as well. P0158 (02 Sensor Circuit High Voltage Bank 2 Sensor 2). I was looking at replacing the sensor but I've read that it may not be a problem with the sensor that causes this code.

I've now cleaned the MAF sensor and the car ran great with no visible vibration for about an hour and then started to vibrate and run rich again. I have taken a video of the O2 and MAF readings after the clean which I will upload later.

Thanks,

Chris

 

Mark - where your issues caused by a faulty upstream or downstream O2 sensor? I've tried to get readings from the upstream ones but my diagnositc reader cannot seem to obtain them. They just show 0 volts all the time.

 

Well guys, I have now had another fault code whilst driving. P0430: Catalyst System Efficiency Below Threshold (Bank 2). No sign of P0158 anymore. I managed to grab the freeze frame data this time so I'll upload it later.

 

Here is the freeze frame data from when the P0430 occurred. Does anyone think this is just because the car is running rich or because of a faulty O2 sensor or something else?


Freeze Frame Data for P0430 Fault Code

 

And I also cleaned my MAF.

Before the MAF clean these where the O2 voltage readings at idle and at full operating temperature.


O2 readings at idle before MAF clean.


After cleaning the MAF here are the O2, MAF and RPM readings across the range from idle to 2000 rpm and back to idle. Also these are taken at full operating temperature.


O2 voltage readings after MAF clean and at full operating temperature.

I may be wrong but my O2 readings do look different at idle between before and after the MAF clean. Could this be the problem?

Does Bank 1 Sensor 2 look odd compared to Bank 2 Sensor 2 as there is a difference between the waves.

Thanks

 

Firstly happy new year guys. Now that the Christmas holidays are out of the way I've started to revisit this problem.

The car has not been used for just over three weeks and has ran great for a couple of days. However, yesterday the car is vibrating again at that rev range, surging when cruising along and often appears to hesitate when accelerating.

I've now captured further readings for trims and O2 readings. I've now managed to get my reader to capture the mA readings from the upstream O2 sensors. I will upload the video later when I get it downloaded from my phone.

Interestingly my O2 upstream sensor on Bank 2 shows 0 mA constantly whereas Bank 1 shows a reading. Could my upstream O2 sensor on Bank 2 be bad? Should there be a reading from it or is 0 ok?

I've also noticed that my Air Intake Temperature is reading 161F (72C). It looks very high. Is that also ok and within normal ranges does anyone know? My outside temp is currently 46F (8C).

Thanks,

Chris

 

Hi all,

I've now got the video from my phone.

It shows 0 mA on Upstream O2 Sensor Bank 2 Sensor 1 for some reason. Not sure if that is correct. At least I now have those readings as well.


Thanks,

Chris