First of all, I have already perused threads on this but am now at a loss.
Took the car out today and running fine. I suddenly had to accelerate hard to make a lane change and when I did, the car stumbled badly and lights came on and restricted performance. I backed off and the car seemed to run fine. I hit it again and the car stumbled badly again. Cleared the codes and tried hard acceleration several time with no issues at all other than my persistent chirp from 6th to 5th gear downshift which sometimes throws a code and sometimes no. Anyway, drove home without issues. My wife took the car out later and it apparently did the same thing to her without hard acceleration. Checked the codes. P0171 and P0174 and I know what they mean. Checked for vacuum leaks all over the engine and even sprayed it with carb cleaner while idling and got no change in idle so probably no leaks. Revved it up in the driveway and it stumbled all over the place. Replaced the MAF since it is not that expensive(to my surprise). Revved it up in the driveway again and it still stumbled and threw the codes.
Any ideas? Why would this come and go and come back all in one day?
Other than the fact that it is a Jaguar?


Thanks

 

You will need to disconnect the battery or remove 'stay-alive' power to the ECM to erase the 'learned' fuel trims. Simply clearing the DTCs will not reset fuel trims!!!!

bob

 

This should be interesting...I don't know; but hope someone does.

 

Not sure that I totally get that response but easy enough to do. We shall see what a battery disconnect accomplishes and respond later.

 

Your fuel trims will show whether it's a leak - there are MANY threads about using them. If you've had the battery off you first need to let them relearn of course.

If they show not a leak, then (in no particular order):
1. could be blocked cat(s)
2. failing fuel pump / blocked filter
3. failing coil(s)

 

How old are your VVT O-ring seals, and are they showing any signs of weeping motor oil below them?

 

Did you buy the right air flow meter? There are many that do fit, but are somehow working differently and giving different readings not expected by the ECU (seems to go against the usual understanding that incompatible part should just not plug in, but whatever). Go by the DENSO number. You need DENSO 197-6030 (does not have to be Jaguar).

That test with carb cleaner proves nothing. You need to do the work and replace all those o-rings. Every hose to the throttle body is a simple NORMA connector (pinch-and-pull), all sealed with o-rings. Replace the VVT seals if you see oil (or just replace them, $20 a pair). Check the dip stick o-ring and the PCV valve. All cheap and easy stuff. Check the big intake hose, top _and_ bottom for cracks.

If you have faults under hard acceleration, check the motor mounts. On failure, they can let the engine rock more than it should and introduce air leaks that are normally sealed. The usual test is to press the brake in Drive (car not moving), and provide some gas, and check if the engine somehow moves/rocks/lifts "too much".

To move forward, you will need to get a tool that reads the fuel trims, like a cheap ELM327. This will also let you monitor the fuel pressure (btw, when was the filter changed last?).

Best of luck, keep us posted.

 

My car was working properly, however my mechanic suggested me to replace two hoses (the two that goes from the engine to the oil radiator), now the car smokes white just once when it starts (but it's like a cloud, white and smells good, not like oil), then nothing. I'm getting the codes lean bank 1 and 2.
Is it any relationship between those hoses and the problem I have now? Because I've sent the car to the mechanic working fine.

 

First, thanks for all of the responses. I have yet to check everything. Drove the car today and it behaved great except for one time under hard acceleration. All other times no issues. No sign of any oil around O-ring seals. I have an ELM 327 and was using it today but did not see where I could monitor fuel pressure or fuel trims. Not really sure what to look for with fuel trims. Is this the O2 sensor reading?
Shows 2 O2 sensors on the Dashboard from the ELM327. One changes and the other always reads zero.
Thought about failing coils too but I have never seen them screw up and later act good. That doesn't mean they cant I guess.
I guess it confuse me in that it won't seem to stay broken.
Intake hose looks good. Dipstick O-ring causing this? That is a new one on me but I will check.

 

Just did a search for "fuel trims" and came up with nothing. Am I doing it wrong?

 

Something is wrong - I just did a search on title only containing 'fuel trim' and got several hits.........

Here is a link to a thread that taught me a lot about fuel trims
https://www.jaguarforums.com/forum/g...ed-quiz-49317/

 

Tanks again to all of you and a special thanks to clyons for the link to fuel trims.
Since I cannot see them with my ELM327, I am wondering if there is a better app to use with the ELM327 than the one I am using which is called OBD Fusion.
Suggestions?
Also, since the trims come from the O2 sensor and I am seeing only changes on one sensor, I have a O2 sensor issue. Bad connections or dead sensor, not sure yet. Would al agree on that?

 

I use TorquePro on Android. People talk about Dash Command(er?) on Apple products.

Check this page. Might help with the exact spelling for the fuel trims: obdfusion

Best of luck, keep us posted.

 

The elm327 can provide fuel trims and a lot more if the software asks it for them - change the software if it hasn't the feature.

 

Okay, in an attempt to unleash the power of the ELM327, I downloaded an app called OBDCarDoctor. It showed me some interesting data that you with more Jaguar experience might help me decipher.
At idle, ST Bank 1 oscillated from 3.12 to 3.91 and SY bank 2 from 2.34 to 3.91. LT bank 1 sat at 19.53 and LT bank 2 sat at 17.97.
I removed the dipstick and then also tried unscrewing the oil filler cap and both immediately gave me the lean codes for both banks. Nothing unexpected there.
I held the car at 2000 RPM and ST bank 1 varied from 10 to 12.5 and bank 2 from 7.3 to 10.94 with LT 1 at 5.47 and LT 2 at 4.69. Raised it to 3000 RPM and number went down more.
Fuel pressure at idle was around 380 kPa.
Took it for a drive and under hard acceleration, both ST banks went to zero and LT 1 to 1.56 and LT 2 to 2.34. Car ran fine. Fuel pressure varied from 282 to 483 when I backed off hard which sounds okay to me.
Added some fuel as I realized that I was about to suck fumes and ran some more.
No codes and no issues other than the 6th to 5th chirp that I shows up occasionally and wont go away despite multiple fluid and filter changes.


Check trims when I got home. over a 30 second period, ST1 varied from -5.47 to 0 and ST2 from 0-3.91. Repeated this a few minutes later and ST1 varied from 0.78 to 1.26 and ST2 from 0 to 1.30. Not sure why that changed.
MAP steady at 31kPA and fuel pressure at 380 kPa
Fuel pressure at a steady highway speed stay around 380kPa give or take 5kPa
So, no codes and no stumbling but lot of information.
I wondered if the low fuel tank level could be part of this but could not prove that.
FYI, this car site 95% of the time and is driven less than 500 miles per year. Fuel break down?
It is rarely if ever driven hard as it only has 300HP so I drive it easily. Maybe it needs an occasional flogging?
I will continue to drive with the ELM327 active and my phone synced to it but not sure what to do now.
All ideas and suggestions appreciated before I give up and trade it for a BMW 330ci.

 

LTFT at idle should be single digits. You have a massive air leak. The air intake pipe on my 06 had many leaks in the accordion section and LTFT's were only around 10.

 

Well, that begs the question as to where it is. I have checked several places and see no signs. Intake pipe seems good. Thought I would hear something as I do when I lift up on the dipstick tube or loosen the oil filler cap a tad. Wiggling and moving seems to produce no changes. Not sure what other seals might cause this nor where they are located.
the LTFT is always in single digits when driving but not at idle which would make sense if the leak was not bad enough to be incapable of being compensated when the air flow is higher under load.
Not sure where to look next nor why it now behaves so well when driving.

 

I would keep an eye on this one. To my knowledge, it should be a pretty rock solid 55 psi (~380 kPa) and not change (say, within .5 psi). This fuel pressure is always relative to intake pressure, not atmospheric pressure, so double check the vacuum line to that sensor (at the end of the fuel rail, passenger side). That vacuum line should be plugged to the underside of the sensor. If it is unplugged or split, it will lead to the wrong fuel as well as an air leak.

If the pressure dropped at high rpm, it points to some obstruction, likely the fuel filter.

Have you checked any of the Norma connectors around the heads, and to the throttle body? These are simple pinch-and-pull, and the o-ring can be changed. Have a assortment.

Have you checked the air flow meter part#?

 

You may need to have a smoke test performed to find the air leak.

 

Ignore STFTs except if you're hunting for an air leak using propane or the like when they go mad if you hit the leak.