I recently had P0171 and P0174 codes on my 2004 XJR. Lean running at idle. Not sure what the actual resolution was or not, so far so good. Needless to say the car failed inspection due to the check engine light. I am interested if anyone has had similar issues or resolution. sorry in advance about the rambling attached tale.

in my attempt to resolve, I thought that the fuel injectors may be dirty leading to misfiring and indicated by extra O2. This is certainly cheaper and easier than O2 sensor replacement. First of all I filled my tank and added two bottles of Chevron fuel injector cleaner with Techron. 15 gallons per bottle so this was a heavy shot. This has worked well for me on other vehicles in the past and comes highly recommended by a well respected mechanic. After 200 miles the check engine light remained on and restricted performance indicator would come on time to time. I then removed the hose connected between the air cleaner and supercharger and removed two small hoses associated with the larger hose. I cleaned all connections looked for obviously signs of air leaks, ie dirty,dust trails and saw one o ring that was somewhat dirty. I cleaned all connections and reinstalled. then used my OBD tool to reset codes. The car passed inspection, but I never saw any major areas of concern and wonder if the the fuel injector cleaner solved the problem all along??
RyeJag

 

Most likely it's a vaccum leak which can be tricky to find. Start checking all the hoses you can see under the hood & under the car.

 

A good bet is it the full load breather, failing the breather tube to the MAF

As it happens I was just about to order both breather hoses plus the full load breather
I'm approaching 150,000km's and its time to do all the hoses that have never been replaced and these to prevent the codes you mention

Cheers
34by151

 

Hi 34 what breathers are you talking about exactly, didn't know the Maf Had a breather!

 

Ah do you mean the Crank case breather hose? What would cause these codes if only happens not under load?

 

Sorry my mistake I meant the throttle body

S/C and non SC have different breather hoses but the parts on the valve covers are the same

The breather on Bank2 (side with the air cleaner) goes into the intake tube near the MAF
Bank1 has the "full load breather". This looks like a vac actuator but is actually a valve
Its is connected to the throttle body. The part number is AJ83695

Both breathers have a mesh screen in the valve cover. This servers both to stop blowback and to reduce the oil scavenging effect

S/C models have an extra vac hose at the throttle body that is used to power the S/C bypass actuator

The EGR system also has some vac hoses as does the secondary air injection system

The usual cause for P0171 is the "full load breather" followed by the hose
For P0174 its the other breather hose and or and intake tube leak

I would just replace both breather hoses and the full load breather. These are all inexpensive parts

Cheers
34by151

 

34 can not having the Oil filler cap done completely up cause a Vacuum leak? I say that because I have been having Bank 1 and 2 lean with short term trims at idle of 19-24this started after an oil change, checked the cap today and it felt tight then it clicked once more and when I connected My OBD I now have -0.8 fluctuating +3. My Long terms where 19.5 but under load ST's dropped to 0.3-3 but LT's stayed at 19.5 due to idle ST's being high. My restricted performance would come on at say a traffic signal then once. Under way would go off just like Ryejag. Sorry to high jack this thread Rye but thought this may be relevant.

 

Yes if you don’t have the system sealed you will have a leak, This includes the dipstick, oil cap and the fuel cap

The system counts on being sealed. The pressure is regulated by the "full load breather"

You can try clearing the faults then do a reset (battery off for 30mins) of the ecu

You will need 2 drive cycles before you know but the reset will clear the long term fuel tims. If you still have big bank differences you will know

I would still replace those 2 hoses and the full load breather a they are cheep and will cause this error at some point. So at the least call it preventive maintenance

Cheers
34by151

 

34by151
all very education for me no objection to hijacking the thread.

This raises another question. Sometimes after the car is started up there will be a small cloud of blue "burning oil" colored smoke. The car does not use very much oil at all, and I thought this could be some valve guide leakage while the car is sitting unused for a few days, it is not my daily driver. Could it be the the MAF valve or breather are not operating correctly and rather than to burn the oil vapors a little bit a time while driving normally, the oil condensate is burned all at once upon starting?

RyeJag

 

Sorry for bad news but Blue Smoke on start usually indicates worn rings or valves
I'd do a compression test first

Cheers
34by151

 

well I also have the lean codes , replaced all hoses & valve breather , removed throttle body cleaned it , also the fuel pressure sensor was clogged when i pulled the vacuum hose off , then installed wrong MAF sensor thanks to dealer for non SC v8 then had running rich codes , now have new MAF sensor and the running lean codes are flagged again , I Give up

 

After all that you need to reset the ESC using the battery off method
On mine I reset the codes, flashed the ecu update. Once i had done the 2 cycles I reset the ecu again

The point being is you need to clear the long term adaptions

If you have Torque you can monitor the 2 short term and 2 long term adaptions
Both short term and both long term should roughly match as you drive
If you are getting a big difference between banks you still have an issue

Cheers
34by151

 

I wish i had the software to update it , Im starting to think that I have a leak under the charger on the intake or something my idling long term is +14 %a +13% on B at idle then at 2500 it goes down , I cant find any leaks anywere Im so Po ****

 

Have you tried the unlit propane torch trick (you can also use small sprays of easy start)?
Monitor STFTs (which I'm assuming are high) will dip when you hit the leak if there is one.
The other possibilities are a dirty or defective MAF - there's plenty of info on how to clean it - or low fuel pressure due to a bad pump or clogged fuel filter.
You can check that at the Schrader valve on the injector rail.

 

Try resetting the adaptions first
Using the battery off method

Once you do that start chasing down the items in this thread

Cheers
34by151

 

thanks, Yeah I reset it several times and drove it 100+ miles , also I Pulled off the fuel pressure sender on rail wich has a vacum line on it the unit was clogged with gunk bad I cleaned it all out ,also replaced fuel Filter under fender, pressure seems hi if anything to me 55 lbs +- , I have not Done the propane trick yet i will soon, the STFT are +- are not way off at all, just LTFT , I did notice a small leak around throttle body were brake booster goes in not much at all , it just make sense I dont think +13,+14 on LTFT are that big of a deal its not 20+ I dont see why its flagging errors


any one have correct numbers for fuel pressure , stft,ltft ?????

 

Fuel pressure sounds plenty, not sure what it should be for an SType.
Your STFTs are within normal (+/- 3% or so) because LTFTs have gone up enough to compensate.
You'll see the STFTs go negative if you hit a leak.
I think a LTFT > 10 % is enough to set your P codes.
They both should be near zero.
YOu need to fix that leak - it's surprising what a small leak can do.
Tho other place on XK's is the underside of the bellows section after the air filter.
Again, not my engine so I don't know if you've got that potential problem.
It won't hurt to clean the MAF anyway.

 

MAF is new ,I just checked the numbers again , +18% Both LTFT , 0-+5%on STFT went around every thing on the intake with propane Didnt see any Numbers jump around .

id like to no what the numbers are supposed to be on the manifold pressure

 

Yes, I forgot you're not the OP who seems to have disappeared, also you've got an R.
I don't have JTIS for an S type but for an XKR 4.2 the rail pressure should be 5 Bar 72 psi. 50 psi is right for a N/A engine so your pressure may be low.
This can be due to a clogged fuel filter, faulty pressure sensor or duff pump but I'd expect you to have misfire or hesitation problems if the fuel supply was restricted.
Doe it run OK?
Why did you change the MAF?

 

It runs great ,I changed the MAF because it was dirty but I also was running a K&N air filter , Now Im back to stock filter , iv went over everything with a fine comb the most fuel pressure I see is about 59 PSI on the laptop while driving and I did change the fuel filter , what was weird was i had the wrong MAF in it for non SC 4.2 and it said it was running rich but man it ran better than it ever did it seemed to gain 50 Hp with the wrong maf sensor in it . Now I got that straight correct part number in it, and now its running lean , she is going on a 200 mile trip in it , il see if there is some new codes when it comes back, also i cleaned the fuel sensor on the rail it was clogged with gunk at the vacum line connected to it , when i disconect the vacum line from it and put a stopper in the vacum line , I see know real diff in the fuel pressure .