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I know there have been multiple threads regarding this issue however i'd like to post my OBD II readings hoping for some advice.
Vehicle is 2008 Super V8 with 80,000 miles.
So upon purchasing the vehicle, a really rough idle was noticeable after starting, however as it was in the workshop i had it checked and have had the TB dissasembled and cleaned.
All seemed fine at least i thought so and i ve taken the time to concentrate on other issues disregarding the fact that codes P0174 and P0171 would pop up whenever i ran torque pro on my phone (OBD II scanner thru a bluethooth module).
Clearing the codes doesnt help and they will re appear within 2 ignition cycles usually P0174 Current Fault and P0171 Pending Fault although sometimes P0171 pops up as Current Fault as well tho much rarely.
I have changed the fuel filter, used some injector cleaners a couple times, changed the air filter, inspected all hoses for vacuum leaks,cleaned the MAF (also took out the MAF from my other X358 4.2 na but no difference) and today have dissasembled the whole intake
up to the throttle body to inspect it once again.
TB seemed clean tho i've sprayed it with some carburator cleaner again however this hasn't helped any. I have also noticed that the TB is not 100% closed and there is a tiny gap that can be closed upon pressing on the TB wing with my finger (not sure if this is correct or not - the tiny gap)
As for Vacuum leaks i have been spraying the carburator cleaner all over the place in every possible place but no changes in rpm have occured. I have ran across every hose and pipe, checked and changed my oil dipstick o ring but to no avail.
I have to mention that there is rough idle but only for a couple seconds when the vehicle has been standing over night and the engine is completely cold, once it is warm its almost undetectable.
So here are my torque pro readings maybe someone might help as to what should i look at next:
So my thoughts are:
1. Vacuum Leak - still somewhere and im missing it.
2. Exhaust Manifold leak or gasket
3. Injectors
4. O2 sensors - but would 2 banks be affected by a faulty O2 sensor on one (unless both O2 sensors are defect) ??
Ahh and here is a pic of the TB from today:
I thought I would deal with this myself however i am about to give up and let some real mechanics do their job (tho i don't trust anyone with my Cat)
Both bank 1+2 LTFT +19.5%..So not exhaust manifold/gasket leak, injectors, or o2 sensors.
The TB is not meant to close 100%,
You should use TB cleaner not carb cleaner to clean the throttle body.
You need to be monitoring the STFT's for bank 1+2 when looking for vacuum leaks, when spraying the carb cleaner, not the RPM..
Have you checked for conformation of a vacuum leak by compering your LTFT's at 650 rpm and 2500 rpm (In park with engine up to temp).
Both bank 1+2 LTFT +19.5%..So not exhaust manifold/gasket leak, injectors, or o2 sensors.
The TB is not meant to close 100%,
You should use TB cleaner not carb cleaner to clean the throttle body.
You need to be monitoring the STFT's for bank 1+2 when looking for vacuum leaks, when spraying the carb cleaner, not the RPM..
Have you checked for conformation of a vacuum leak by compering your LTFT's at 650 rpm and 2500 rpm (In park with engine up to temp).
Sorry, I did use a TB cleaner but i guess thats not the issue.
During driving today at a 90% load at 3450 rpm I got 60 PSI fuel pressure with 1+2 LTFT at 3-4 %
The higher the load the lesser the problem at least thats what it feels but a 0-60 sprint is over 6 seconds plus you can just feel that delay once you kickdown (its a split of a second but enough to know something ain't right).
[QUOTE][
4.2 NA or SC engine? If NA then yes, one pump only. I thought the Super V8 model carried the SC engine.../QUOTE]
I haven't seen a NA in a super either. ?????? Need to confirm the model.
When FT drop at 2500 rpm is usually is vac leak. It's RPM not load.
Last edited by Mark in Maine; Sep 8, 2019 at 09:09 PM.
4.2 NA or SC engine? If NA then yes, one pump only. I thought the Super V8 model carried the SC engine...
[QUOTE=Mark in Maine;2124081]
[
4.2 NA or SC engine? If NA then yes, one pump only. I thought the Super V8 model carried the SC engine.../QUOTE]
I haven't seen a NA in a super either. ?????? Need to confirm the model.
When FT drop at 2500 rpm is usually is vac leak. It's RPM not load.
To be clear I am talking about the 2008 X358 4.2 Supercharged ending VIN: H24...
I own two, the other X358 is 4.2 NA.
Ok, I thought i have one pump this is how it looks:
behind driver behind passenger
Shouldn't there be a connector on top of the passenger side if so ?? (Harness - Jaguar (C2C37645)) ??
Hi, you're correct after 2006 the supercharged models went to one fuel pump.... and the general conclusion is that they run at a slightly lower pressure.
I had a similar issue to you - before I changed the supercharger and I would suggest that you check vacuum leaks at the below points - in no particular order. However I would say that there are some common suspects, mainly the brake booster point on the intake and also the supercharger outlet ducts.
Secondary air injection lines - they are hard plastic and become brittle, also the vacuum tank in the wheel well may not have a good seal.
Supercharger outlet ducts,
part load breather hose & full load (but I'd say less so),
The intake pipe especially at the corrugations,
Brake booster take off - o-ring
My issue was the fuel purge valve solenoid point where mounts to the intake below the TB, the bracket was not holding a good seal and was allowing un-metered air in.
The below image was after i had got everything fixed... the fuel pressure looks fine to me. I see a max of 75psi ish on full throttle.
I'll keep on looking, maybe do a smoke machine test.
The points You mentioned are all worth looking at, tho accessing points below the TB might be easy if I had a trained racoon to do it for me.
One other thing worth mentioning is that the other day while checking all the lines i ran into a broken pipe that runs to the fuel pressure sensor. I've replaced it with
a reinforced rubber hose and tightened with clamps. This however did not fix anything and i suspect i accidently broke the plastic hose myself right before when i was
inspecting it - as You said those plastic hoses at their age of over 10 years are soo brittle.
You'r readings are similar except for pretty good trims compared to mine now. Yes the pressure jumps to about 70 psi and performance wise at higher revs the car
seems to do fine (so im betting on a vacuum leak somewhere as well).
Anyway here are my readings from today with min and max data from a 10 km drive while the snapshot is taken at idle:
I'll keep on looking, maybe do a smoke machine test.
The points You mentioned are all worth looking at, tho accessing points below the TB might be easy if I had a trained racoon to do it for me.
One other thing worth mentioning is that the other day while checking all the lines i ran into a broken pipe that runs to the fuel pressure sensor. I've replaced it with
a reinforced rubber hose and tightened with clamps. This however did not fix anything and i suspect i accidently broke the plastic hose myself right before when i was
inspecting it - as You said those plastic hoses at their age of over 10 years are soo brittle.
You'r readings are similar except for pretty good trims compared to mine now. Yes the pressure jumps to about 70 psi and performance wise at higher revs the car
seems to do fine (so im betting on a vacuum leak somewhere as well).
Anyway here are my readings from today with min and max data from a 10 km drive while the snapshot is taken at idle:
im pretty sure the LTFT’s only go to 19.5% so it would be interesting to see the short term trims also?
Are you able to spray some flammable spray ( carefully!) near to the intake components and watch the short term trims in real time on your phone?
can you drive at a steady speed and watch the short term trims?
So here are the readings on a hot engine parked at idle:
So I did spray the cleaner all over the place and i did get a hit ! (at least i think so) .... Spraying at the rubber joint of the intake manifold and the TB generated a slight jump in revs and a drop in STFT. Hopefully i'll be able to check it out tomorrow. Btw LTFT during driving drop to around 3-5 % while STFT would hit around - 3-4 % but it just shows how the ecu is compensating for the lean conditions and then vice versa when extra fuel is injected. I'll post up more when i locate that vacuum leak. Cheers.
Sorry to join your thread so late but I'll add a couple of comments. 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 that I don't think has been mentioned 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).
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.
After some time and about 2 weeks in a garage (had the mechanic do the job in between other jobs) the vacuum leak has been finally located and problem solved (I hope).
The parts above had to be changed due to either being suspected of causing the vacuum leak or while searching for it have been damaged by my clumsy hands or for being soo damn brittle. The EGR coolant hose was surely my mistake when foolin back there with a screwdriver (tryin to push the vacuum pipe behind the TB). Also the rubber flange that connects the intake manifold to the throttle body had a pin size puncture and had to be changed.
Now this rubber flange is part of the alloy intake manifold on the SC 4.2 engines and is not available for sale. Did some research here and on my own and bought this:
It had to be cut to match the height of the old rubber connector but eventually it works fine (its not as elastic as the previous rubber - some carefull fitting needed).
So I picked the car up today and all seems well (no lean codes, throttle response seems ok, fuel trims ok).
Will do some more performance testing in the upcoming days but hopefully this should be it !
I Thank All contributing to this post and hope it helps others in the future (now know what a pain in the *** the lean codes are to diagnose and locate !).
New intake pipe fitted during the whole deal U can see the blue rubber flange connecting the TB and intake manifold The fuel pressure regulator was also changed and the visible pipe going to the regulator changed as it was brittle and cracking as well. First thing done actually.
P0174 and P0171 on super V8 + data output
