Hi all, I recently had a P0171 code (lean bank 1) and noticed a leak in the plastic intake elbow. The scanner then was showing around 20% LTFT at idle. Since replacing the elbow, the fuel trims returned to normal.

The code came back and the LTFT shows bank 1 at 5.6% and bank 2 at 3%, so bank 1 is definitely higher, but is there a reason the code is being generated at only 5%? STFT is within spec, but I noticed once that bank 1 had a higher LTFT than bank 2, but with a significantly lower STFT. Not sure if that meant anything but usually the STFT is similar.

I recently changed the fuel filter, cleaned the MAFs, tried BG44k fuel treatment, but the code keeps coming back. Will be taking it to my mechanic, but wanted to understand if this is an issue and why?

I’ve been scouring the forums and doing some diagnosis but can’t seem to find a solution that works.

 

Are you reporting the freeze frame data from the code? (I doubt it, because it will show much bigger trim(s).)

If you're reporting trims other than then, you're not seeing what the car was doing when the code flagged.

 

Have you read live data on the O2 sensors. If you look back at my issue, I chased it for ever, and found lazy O2 sensor.

 

Many seem to classify, or view them as a wear part, and just replace them much like spark plugs, belts, etc.

 

I’m newer to this so just trying to learn, but I did have a real vacuum leak that tripped the code, but now that its fixed, would the same code be tripped again for a different item (e.g. lazy O2)? What would be the best way to diagnose it?

I’ve attached the freeze frame data but I’m not sure what looks wrong

 

Your trims are too high on both. They are similar both left and right. Don't think it's O2 sensors. Seems like vac leak, as both are same ratio. Do your trims drop at higher rpm vs idle? I see the data is at 1514 RPM.What are the current codes.Need readings at idle and higher rpm to determine.

 

Hi Afraaz3,

It is not uncommon for an air leak that affects both banks to trigger a lean code in only one bank. As Mark mentioned, your engine is running lean in both banks.

A very common area for intake air leaks on the supercharged engines is around the Helmholtz resonators that are molded into the air intake pipe between the MAFS and the metal pipe on top of the supercharger. These resonators help control resonances to reduce induction noise.

On at least a couple of these cars I've found that where the bottom cylindrical resonator connects to the main pipe the ultrasonic weld was failing, creating an air leak right at the seam, which made it difficult to see without manually moving the resonator side to side relative to the main pipe.

On another car, I found the plastic on the resonator to the left (while facing the engine bay) was deteriorating at one of its end "corners."

In all cases, cleaning and sanding the damaged area and patching with plastic bonding epoxy cured the leaks.

Another common leak point is the plastic pipe to the cam cover vent on the right bank (left when facing the engine bay). The vent looks like a PCV valve but isn't actually a valve. Replacing the O-rings on that plastic pipe has cured P0171 on a couple of cars I've serviced (XJR & S-Type R). I don't think this is your only problem but it could be contributing to P0171 triggering without P0174.

Also, I have found that using TB cleaner or other flammable spray is not very effective for finding leaks on these supercharged engines, even while watching the fuel trims on a scan tool. A smoke machine will expose leaks in 10 minutes or less, and you should re-test after each leak is cured because there may be more leaks farther downstream.

If you still have lean codes after curing or ruling out intake plumbing or vacuum leaks, the intake manifold gaskets may be suspects.

Cheers,

Don

 

I could not find mine with TB cleaner or propane. Smoke it !!!!

 

Bank 1 is about 8% at idle and bank 2 is at about 4%. Under throttle they both stay under 20%. Thoughts?

 

Try reading about my past issue. Many top veteran forum members were involved to solve my lean issue. It appears that your trims are up and down, by your graph. I can't clearly determine rpm on the graph. It would help to see both stft and ltft and rpm. Lower down on my post (pg 2) some of my issues may sound familiar to you. Also as you will read, we figured it out by reading voltages on the sensors. Have you had it smoked yet? Both sides are out of limits L and R almost identical. This surely looks like vac leak vs O2 sensors. Your first freeze frame appears @ 55mph. Your first trouble shooting readings should start in the drive/garage not under load. Reading while moving introduces to many variables right now at this stage.

https://www.jaguarforums.com/forum/x...74-sv8-177741/

 

Update: I got the car smoked at a local shop and we saw there was quite a bit of smoke coming from the intake area. It could of course be either the gaskets, or the intake itself. That being said, is there a reason this could would be flagged mainly at higher speeds around 55-65 mph? It went away last week but then comes back intermittently so I want to be sure it’s just the gaskets if possible.

Is this a job worth doing myself given labor is quoted at 6+ hours? Any paint points like easily broken hoses, plastics, or hard to reach bolts that make this a job worth having someone else do? It’s quite a bit of cash I would hate to waste on just a gasket job

 

Best way to learn what you have, how it works, & what is wrong, is to fix it yourself.

Get off your rump, on your feet, & get busy.

 

Smoke'em if you got'um!! Your lucky you found your leak with a smoke test. Some of us could not find our lean code cause after many smoke tests.

 

If the intake manifold is removed, i would replace those eight gaskets inside as well.

The valley hose, thermostat with housing, water pump, tensioner, idler pulley bearing, with a new belt while your there.

Look at the hoses, replace any suspect ones, you should be on your way to enjoying your Jaguar.

 

Thanks all, I’m looking through the JTIS manual and see the 4.2 NA is used in the illustrations. Is there any difference in doing this job on the supercharged? I can’t seem to find some of the easily labeled components (e.g. Engine cover brackets) and some shops are charging more labor (between 6-8) for the R version.

I mostly only have amateur experience doing suspension rebuild and haven’t touched engine work. This is the R so I don’t think there’s a valley hose under the intake since it’s under the supercharger, the water pump is the metal version I believe, and the prior owner already did the idler, tensioner, and pulley. I will check the thermostat housing to replace with a new metal one if it’s plastic.

 

If anything, change the valley hose, or you will be removing the whole thing again in the future. The labor involved in changing the valley hose make the part itself really really cheap. No one in there right mind on this forum would pull the SC and not change the valley hose.

 

Thanks, I haven’t gotten a consistent answer around manifold removal for the supercharged engine, but its sounding like on these engines, the whole supercharger needs to come off, making this a significantly more difficult task than on the NA engines? Let me know if that sounds correct, or if the manifold is removable without messing with the supercharger.

In that case, I’d probably want to have the supercharger rebuilt, change the valley hose, knock sensors, and the manifold gaskets while i’m In there. On the R, I heard the water pump is metal and doesn’t need replacing. Is that correct and is the thermostat housing metal as well?

 

Hi Afraaz,

I don't know if you are using the electronic version of JTIS or the pdf Workshop Manual, but in the pdf manual I believe there is a separate section on the 4.2L S/C engine that should answer at least some of your questions.

On both the N/A and S/C engines the water pump housing is aluminum but the impeller is plastic, because the OAT (Organic Acid Technology) coolant is poor at protecting metal impellers from electrolysis and cavitation erosion, so be sure the new pump you buy has a plastic impeller. The one Jaguar currently supplies as a replacement is made by Airtex and is available at Rock Auto for less than $40.00.

Your thermostat housing and outlet pipe are plastic and I don't know if aluminum versions are available, but replacement plastic ones are available from sources like our forum sponsor SNG Barratt.

EDIT: I just received an email from forum sponsor Welsh Enterprises and they have the thermostat housing and thermostat currently on sale. Check to be sure it is the correct part for your car:

https://www.welshent.com/Jaguar-Ther...m_medium=email

Cheers,

Don

 

I want to try this smoke test! is this something i can do at home? kits available? I am all about diagnosing failure modes!

 

If your a smoker, you will need a piece of the right size hose, to connect, then puff away.