Hi Guys,

Upgraded from my 2002 XJ8 Sport to a beautiful Black 2006 XJR, Black Leather Aluminium door and dash trim, Rear Entertainment system, 20" Sepang alloys, 130K on it, but having said that, it's been very well looked after, and has only covered just over 1000 miles in the last year and a bit. Got it for what I think was a steal from a guy in Edinburgh. who was selling off his late fathers estate, including an E-type, and a 1972 Yellow Rolls Corniche.

Tidying up a few minor issues with it, had it a few weeks now, all good, except, had the Air Con regassed as it was not working at all, so was well pleased when it took and held a regas, replaced 2 broken dash vents, 2 dull wing repeater lamps and bought 2 XJR wing badges. not sure if these are suppose to be on it, but all it has is the boot badge and a rather naf plastic rear number plate plinth with a faded "supercharged" badge on it, that's coming off asap.

Anyway normally the first thing i do when I get a new car is get it up on a ramp and give it a right good going over, but I have literally been so busy, I haven't had a chance. but hopefully soon. All fluids and lights are fine, no leaks, no burning smells, plenty meat on the brakes, a folder full of receipts for work done, including a gearbox oil and filter change in June this year.

It drives really smoothly, loads of power, a nice V8 rumble from in the cabin.

The only other obvious problem so far is the MIL comes on every now and then with a P0171 code, no other codes confirmed or pending. Most of the faults in the list for this code, normally come with another code, which would point to a specific component, fuel filter, fuel pump, MAF, EFT, and other sensors, but P0171 appears to only affects Bank1, so it can't be any of the sensors listed, as if they had a fault it "should" affect both banks, so Id get maybe a P0174 as well. So just on that alone I believe I can short list the possible faults to, Bank1 and one or more of, a Misfire, a restricted Fuel Injector, the bank1 HO2 sensor. I suppose I still can't rule out an air leak, but I feel that an air leak "should" affect both banks.

Sorry this is more of a "think out loud" than a question, but any input would be greatly appreciated.

Thanks for reading
Brian.

 

Hi Brian


The Supercharged 4.2's did have a few issues with some of the inlet gaskets to the charge air coolers at the top. Sometimes you can get away with loosening the bolts and readjusting them ( they have some movement ) can help. Other things I've come across with these is 02 sensors, seen quite a lot of them go faulty, and if left long enough, the cat itself will fail.


Just make sure you don't have any actual misfires at the moment. Check all the basics, air filter and fuel filter are fairly new. Make sure all the intake pipes are nice and tight, no vacuum leaks. Once you've check and ruled this out, you can try swapping the upstream 02 sensors from one bank to the other to see if code shows for bank 2 this time.


Let us know what you find

 

Thanks for that, all sounds good, soon as I get a spare few hours I will go over all the items, was going to change the filters anyway.

I washed the car today, and used one of those Air Con Bombs inside to sanitise, so I had it running as I washed it, and that's when i noticed that there is a subtle "hunting" at idle, that seemed to gradually get less distinct as it warmed up. I'm guessing a possible air leak, maybe like you say gaskets or loose bolts.

 

Yep, quite possible.


Next time you start it from cold ( sitting over night ), have a can of brake clean and spray around the air intake pipes, around the throttle body, the charge air coolers, etc. and see if the idle changes when that happens. This will help locate where the vacuum leak is ( if any ).


Also, about the wing badges. In the USA, we had the R badge below the side indicator for the North America market. Here in new Zealand where I am now, they only have the badge on the boot lid. Must have been a market spec.

 

Thanks JBzXJ40, will give that a go.

I put the "R" wing badges on above the wing repeater lamps, I think they look ok, and stand out as the car is Black.

 

I finally got a chance to get it up on a ramp last night, underside looks good, bushes all look reasonable, no movement, but think I'd consider changing them all for poly bushes, where possible. Only thing I could see that needed fixing was the under tray, which is cracked and broken in a couple of places and held up with tie wraps.

I also found a vaccum pipe off under the engine cover, one of the thin tubes that goes all over the engine, and into the PCV unit on the right hand bank, I thought that I had found my P0171 cause, but it's back again, so will have to go looking again.

I tried to use the phone early yesterday and it came up with the message telling me " handset in use", I then remembered I had removed the centre console a few days ago to replace the Dash Air vents and removed it again to check the wiring, found i had left a plug out at the rear of the console, behind the vents. plugged it in and all good again.

I had my blue point hand held scanner plugged in last night, and went on a night time drive, recorded some live data, and freeze frame data, but I can't find my hook up cable to plug it into the PC, soon as I find it, I will upload the files.

I started the car and started driving, then had to stop and I spend 5 mins tapping the time clock as it wouldn't light up , before I then noticed that the buttons around the touch screen were not lit either, and thought, I had done something else when I had the console out, before I realised the daytime running lights were active and I needed to actually switch on the lights to get them all to light up.

Brian.

 

OK so I can't get my Snapo Microscan to work on Windows 10, I also have an Autel Maxiscan MS509, which also will not connect to my PC. SO I will have to just type in the data from the freeze frame, and Live data.
MaxiScan

Stored codes :- P0171 System too lean Bank 1

Freeze Frame Data :-
Fuel Sys1 CL
Fuel Sys2 CL
Load_PCT (%) 41.2
ECT (C) 167
SHRTFT1 (%) 19.5
LONGFT1 (%) 19.5
SHRTFT2 (%) 3.1
LONGFT2 (%) -3.1
RPM 1511
FRP (kPa) 53.1
MAP (kPa) 22.2
VSS (km/h) 25
SparkADV 32
IAT 95
MAF 4.179
TP (%) 22.4
AIR STAT OFF
Runtime (sec) 130
EGR_PCT 63.1
EGR_ERR -4.7
EVAP_PCT 0.0
FLI 94.9
BARO 29.5
VPWR (V) 13.886

There is more, but I think these are the important ones.

 

Confirms the P0171. Time to check for air leak(s).

 

Yep, your fuel trim for Bank 1 is high, should be below 5%. If you cant hear anything physically, then I would try using the brake clean trick, but try to do it when the engine is still cold.


The other thing I see that is a little weird to me in the readings is the PCT Load, 41 %, which tells me you're pressing on the gas ( almost half throttle ) yet your MAF is still reading 4 ( grams/sec ), vehicle speed is 25 km/h. Your MAF reading should be higher than that as your not at idle. Idle is usually around 6/7 from my past experience. I have seen where the MAF sensor can cause lean codes, keep this in mind if you don't find any air leaks.

 

had a listen today and can't decide if there is a "hiss" or just belt noise. if the weather dries up this afternoon, I will get stuck in.

Yeah, I had noticed on live data with the engine off the throttle was sitting at around 14.5%, and at WOT it was showing around 78%. I would expect it to be lower at rest and higher at WOT.

 

A leak you can't hear is usually the cause - if there's a leak.

 

You can buy a party fog machine from eBay, hook it up to the intake and fog her up. You'll see the fog coming out of your leak. This is how I found a missing rubber o ring for the brake booster at the intake elbow behind the supercharger.

 

I was looking at smoke pellets from screwfix, they come in a tub of 10 for about £4, or 50 for £15, not sure how much smoke they would produce, but for £4, worth a try. But a fog machine, might do even better.

 

So I tried the smoke pellets, alas, not enough force to push the smoke around the intake, so Will get myself a fog machine and give it another go.

I Removed the spark plugs and gave them a clean up, A bit of a pig to get out, but I got there, Bank 1 were all sooted badly, Bank 2 were still a bit black but not as bad.

Checked as many pipes and hoses as I could but seen nothing untoward, but did notice a bit of coolant around the top if the expansion tank, and on inspection, found that if I push the thinner top hose just a tiny bit, I get a squirt of coolant, so looks like there is a break in the pipe, does anyone know if there is an upgraded Tank available, like maybe metal replacement?

 

Go a fog machine yesterday, set it up on the car today, engine was warm as I had a few things to do before I got to it.
used an old radiator hose, that fitted over the machines outlet perfectly, removed the filter box and intake hose and shoved the other end into the intake, blocked around it with rags and fired up the fog, not a sniff of smoke from anywhere except the very small amount leaking past the rags.
Next I got it up on a ramp and took off the undertray, the idea was to remove both upstream O2 Sensors and swap them around, as JBzXJ40 suggested, unfortunately, the Bank 1 upstream sensor has been cross threaded and was a pig to get out, the Bank 2, came out no problem, i tried very carefully to screw that one into bank 1, but wasn't happy, and didn't want to end up with 2 cross threaded sensors, so cleaned them both up and refitted them where they came from, Bank 1 went back in and tightened up, but didn't want to force it as it felt tight but would still turn, thinking, maybe it's never been fitted tightly enough and is letting gas out, could this be the problem?? anyway, ordered a new one up, be here on Monday. then I will use the new one in Bank 2 and get a thread chaser or a tap & die set to help clean the threads on the Bank 1 Cat, and fit the old Bank 2 sensor, failing that, i may need to replace the Cat.

After I took out the spark plugs and cleaned them up the Bank 1 STFT went from 19.5 to 18.8 and apart from the odd fluctuation where it dropped to - figures, it pretty much stayed there, after i did the smoke test and the O2 sensors, it has jumped up to 20.4. but the LTFT has stayed constant at 19.5.
Bank 2's figures are spot on.
I will upload more data from the reader soon.

I also found a brand new Jaguar Radiator Header tank on Ebay for £58, half price, snapped it up and fitted that this morning, also a bit of a pig to fit, Literally no room for the shovels I have for hands, 3 other hoses routed over the top of the bottom hose, which is on with one of those self locking paper clip things, managed to get that off and not lose it, then the hose still wouldn't budge, had to mess about for ages to free it, but got there in the end.

 

Maybe a blocked cat.

With an air leak you'd expect LTFT(s) to drop when you rev (parked, hot engine).

 

Hi folks,

I'm reading this with great interest as I seem to have almost exactly the same problem with my 2006 XJR. No misfires, no power issues, it's running just fine. I just had what started as a very sporadic (every 5,000 miles or so) P0171 code. I has slowly become more frequent to a point where I have to do something. It doesn't trigger under light or heavy loading, usually about 25% throttle at 70mph(ish) having just accelerated up from low speeds.

I have tried the throttle body cleaner trick to find a leak and not a twitch in rpms, so for now, I'm going to discount this as the issue.

Over the weekend, I did swap over the upstream O2 sensors, took it out to re-create the trigger and bingo, it threw a P0174 code. So, I decided it was a bad O2 sensor. Unfortunately, it has since thrown both P0171 and P0174 codes, so it's more than just the one sensor. Perhaps it's both??

Next time it triggers, I'll record the data and list it for any advice you can kindly offer. One thing I do remember though from this afternoon is that at 22% throttle at 70mph, the MAF was 5lb and the fuel pressure was 45. From what I see, this looks low.

I'm definitely an amateur who knows enough to be dangerous, so thanks everyone for any help you can offer!!

 

Start with hot engine, parked, or you drown in near-useless data.

 

Could it have thrown the P0171 code with the "new" sensor because the fuel trims hadn't had time to reset?, seems strange that it sets both, when only one showed a code before. Maybe if you do a hard reset, and then let it all relearn.

I haven't had a chance, yet again to do anything, it will be the weekend before I get near mine, but I was planning to replace the Bank 1 Upstream sensor, Ideally I would want to swap the 2 sensors around first, but with the threads knackered on the Bank 1 sensor, I would be better just renewing it. But i read on another thread earlier that on these cars, the downstream sensor does have a bearing on the fuel trims, so was thinking of just changing both on Bank 1, the downstream sensor seems to be about half the cost of the upstream, so not a great expense to change them both out.

Another thought, what if the original bad sensor has cause the second in that bank to go off, and now that you have swapped the upstreams it makes no difference because the downstream for that bank is goosed too? or maybe just clogged up with soot because of the over fueling, maybe swap the downstreams too then see what happens.

 

Guys,

Thanks for the comments and advice. I wish I had the ability to get live data from my OB2 scanner, but it's not that advanced. I can only get freeze frame data when it actually triggers the MIL. I did do a full erase last time to be sure anything else is now new. I only went to work and back today (90 miles) and it didn't throw up any codes. I'm going about 250 miles tomorrow, so let's see what that does.
I like your idea Brian, guess I could swap both downstream sensors to see if the P0171 goes away completely on the left bank.

I'll report back tomorrow.

Thanks!!

Chris.