Hi Everybody,

First of all, excuse me for my approximative English : I'm a French Guy passionate by Jaguar.
In france, we still have Diesel models but I come for my petrol version : Jaguar XJR 2007 4.2 SC.I’m having an issue with my Jag: codes P0172 and P0175 keep coming back, sometimes accompanied by a fuel smell under heavy acceleration.
Here’s what has already been replaced on the car (which now has 226,000 km):

• Fuel pump in the tank
  
• Spark plugs
  
• Ignition coils
  
• Stainless steel exhaust system with 200-cell catalytic converters (and oxygen sensors)
  
• Fuel injector cleaner added to the fuel
  
• MAF sensor cleaned (I believe it was last done in 2021)
  

I’ve identified a vacuum leak at the throttle body mounting bracket, which I still need to fix (apparently a known issue).

Correct me if I’m wrong, but this would only make my rich code problem worse, right?
I’ve checked the EGR pipe, and it appears to be intact.

(Bit of work done myself on this car : trans fluid change / front shocks / air suspension compressor / Airbag light)

Any suggestions?
Already took a look on subjects of the forum ...

Thanks a lot!

 

Hi Trousset. It can be anything related to intake leaks: throttle body, EGR valve, hoses, manifold gaskets. Perform a smog check on a cold engine. It costs nothing and will help you to avoid unnecessary parts replacement. Recently I've had a leak from the EGR valve, not from the metal hose, but directly from the bottom of the coil, there's no gasket there; the black plastic is only pressed against the base. I would never have figured this out without a smoke generator, I would have been looking for a broken pipe, etc.

 

Repair the vacuum leak at the throttle body and then have a smoke test performed to determine if there are other vacuum leaks around the inlet manifold. Since the DTCs are for both cylinder banks, there is most likely a common vacuum leak.

If you have an OBD reader, look at the Long Term and Short Term fuel trims (LTFTs & STFTs). Once the vacuum leak is repaired, the ECM/PCM will compensate by making the fuel mixture more lean.

 

Thanks for your answer.
So you think the vacuum leak can cause rich codes?
I read P0171 (too lean) for a vacuum leak instead of too rich (P0172).

My LTFT are -13%/-15% at idle
It can reach -17% when i press the gas pedal.

Thanks !

 

Thanks !
In fact I have an intel vacuum leak where the brake booster lines connect behind the throttle body.
My doubt is that we often read lean codes for this type of leaks but not rich.

No matter, I have to fix this leak.
I’ll do it myself, I already see there is no more place to work, but this is the game of Jaguar’s owners…

 

@trousset , sorry to hear about your issues.
Given that you are smelling raw, unburnt fuel in addition to the DTC, I would first suspect a faulty sensor. What is your fuel rail pressure reading? What about MAF at idle and under load? Another candidate is the MAP sensor. Since it is both banks, I don't think a bad injector is likely. Is it possible you have exhaust leaks at the manifold/downpipe connection?

-j

 

@Jacuar Thanks for your answer !

1h ago, I took a picture of data’s 2/3m after the cold start.
I think that MAF values are a bit high.
As you can see at the top of the MAF, I think it has already been changed in 21.
A cleaning didn’t change anything.
So this is not the culprit for me …

Don’t know what is the “normal value” of the MAP for this 4.2 SC Engine.

I also thought about an exhaust leak but I don’t think so : no calamine near to the cat when I’m under the car.
A bit difficult to see the manifold because of the shield, but no “tic tic” noise when cold or something else…

 

Hi
@PeterX358, @Jacuar , @NBCat !
Just changed the vacuum seal!
Not as complicated as other people can say!
But not a lot of space.

However, still have the problem (and worse) because Now i have LTFT -15% and STFT -6%.

Do you have any suggestion ?

Thanks a lot !

 

@trousset congratulations on replacing the throttle body gasket, a good thing to address regardless.

Unfortunately, an intake leak will not cause a rich condition, it does the opposite (too much air relative to fuel = lean code). An intake restriction, such as a dirty air filter will cause a rich code (too little air relative to fuel = rich code).

The following are the faults that will trigger the rich codes:

Restricted air filter
Leaking fuel injector(s)
IP Sensor fault (high fuel pressure)
EFT Sensor fault (high fuel temperature)
MAF Sensor fault (high intake air flow)
HO2 Sensor(s) (1/1, 1/2) harness wiring condition fault
ECM receiving incorrect signal from one or more of the following components:
ECT Sensor, MAF Sensor, IAT Sensor, IP Sensor, EFT Sensor, TP Sensor

Are you getting any other codes besides P0172 and P0175?

 

@Mac Allan , thanks !

In fact, I had the same opinion that an air leak don’t cause a rich code.
But I had to fix it…

Could you scroll up and take a look to my MAF and fuel pressure values ?

I don’t want to blame fuel injectors because it’s a bank 1 and 2 fault, and a fuel cleaner didn’t change anything.
Coils, Plugs and Air filter changed.

Unfortunately, I don’t have any other codes…

Any suggestion ?😀

 

@trousset When you replaced the exhaust system did you put in new oxygen sensors or did you reuse the old ones?

 

Hi guys, let me jump in with the same issue on my newly acquired 2005 XJR - I did pretty much the same thing as the OP with no success so far.
I`ve been seaching for air leaks as well but any leak will give you a lean condition. I pulled the vacuum hose on the fuel pressure sensor and the Short Term Fuel Trims went from -12% to +10% due to the additional unmetered air. So it can`t be an air leak that`s causing the issue.
I read in another post only to use a Denso 197-6040 MAF sensor but the MAF in the pic (and mine) are different numbers (I have the same sensor as the OP).
The fuel pressure stays pretty much around 3,8 bar even when I pull the vacuum hose - shouldn`t there be a change?

How can you tell that any of those sensors isn`t working as it should? Are there reference numbers e.g. for idle?

 

@trousset thinking about it and realizing that you have the superchargered engine, an intake leak *after* the supercharger might cause a rich code. The same MAF is used in both the naturally aspirated and supercharged engines, so I would imagine the ECM has to make a boost calculation adjustment. I'm not certain, but theoretically if the boost pressure is greater than or equal to the vacuum, you could have air escaping rather than excess air getting sucked in to the intake. So there could be more fuel relative to the ECM's expected air volume.

Perhaps someone with more supercharger expertise can chime in.

 

Here are my baseline values for my Super V8. Not quite at normal operating temp.

 

Those are pretty much the same numbers I have - today I changed the MAF sensor to the suggested version and the MAP(!) which changed absolutely nothing. The only difference I can see is the throttle position percentage which shows just 5.5% in idle while yours shows over 14%. I don`t know if that affects anything but the next step would probably be a new fuel pressure sensor and a set of new injectors as everything else is pretty much new now :-(

 

Maybe it is enough to replace the rubber gaskets of the fuel injectors. In any case and although in one of the previous posts the causes for the rich codes were mentioned, I have attached the DTC list for your information.

Best regards,

Thomas

 

I have this exact code which doesn`t go away after deleting the P0172/P0175 which is mentioned in other posts as being "normal" and that it could be ignored. In the DTC list it says "DTC P1000 is flagged after DTCs have been cleared, all engine management OBD diagnostic monitor drive cycles HAVE NOT BEEN COMPLETED". Maybe I`ll start from there but why should the rich conditions go away from that alone.

 

On these cars what does the throttle actually control? The throttle controls the amount of air entering an engine, fuel is controlled by the ECM. To make the lean vs rich problem simple -- excess air or fuel restriction = lean, air restriction or excess fuel = rich.

Given the 5.5% at idle, that's a ~60% reduction in air entering the intake, which I would think will cause a rich condition (too much fuel relative to air). Are you seeing any codes other rich codes?

 

Thanks for the input, there`s only the rich codes and P1000 which I can`t delete (yet). I`ll check the percentage range of the TB from idle to full.

 

At this point don't worry about the P1000 code. Each time you clear codes, that causes the P1000 code. The P1000 code means the onboard diagnostic system has not completed its readiness tests, and it takes several drive cycles to pass all the readiness monitors.