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My check engine light came on for,
P0174 bank 2 combustion too lean
P0171 bank 1 combustion too lean
P0101 mass or volume air flow circuit range/performance
I drove down to a quarter tank of gas and added Liqui Molly & drove her to almost empty, hoping this would clean the fuel injectors. The check engine light is still on.
What should I do next?
My car is a 2008 XJ8 L with 43,000 miles
I'm in the USA
Thank you for your help!
Last edited by GGG; Jul 6, 2016 at 05:55 PM.
Reason: Emphasise Model & Year
The manual explains and gives the most likely causes for each code.
P0171 and P0174 are very common codes and the most common cause is an air leak in the intake somewhere between the MAFS and the cylinder head (this includes the intake air plumbing, throttle body gaskets, intake manifold gaskets, etc.). A much less common cause is fuel filter restriction. Fuel injector restriction is another possible cause, but it's extremely rare that injectors in both banks would be sufficiently clogged to trigger both codes. The same applies to engine misfires - usually only one of the two codes will be triggered because the misfires are only in one bank (often just one cylinder).
P0101 can also be triggered by an air leak, or a blocked air filter, corrosion on electrical connectors or grounds causing high resistance, or other causes.
My recommendation would be to first check for loose connections in the plastic pipe between the air filter housing and the intake manifold. Check also for any cracks in the intake pipe or the smaller breather hoses that connect to the cam covers, etc. It is easy to remove the air intake pipe for examination. It is Part 2 in the diagram below, and you just need to loosen the two hose clamps, Parts 7:
The breather hoses will look like Parts 1 and/or 4:
If you have a flammable liquid spray such as starter fluid on hand, you can try spritzing or misting some around the various areas of the air intake and breather hoses, listening for the engine to briefly increase in rpm, indicating a leak where the starter fluid has been inhaled into the intake. Professional mechanics use a smoke system to find leaks.
I had same problem. I knew that if two banks were lean it has to be a leak. but After replacing all the O rings adding one to dipstick and finally a smoke test. No leaks. I changed the MAF sensor but not OEM Autozone. Code remains. Ordered a OEM one and problem has been gone for over a year.
These codes are triggered when un metered air enters. Either a leak or in my case a faulty sensor giving false readings.
I also had codes P0101, P0174 and P0171. In addition, I have had code P0430 for quite some time (catalytic converter bank 2 does not operate properly) with a check engine light coming and going but being on more frequently in recent time.
Long story short, I installed a new MAF sensor and that seems to have fixed the problem. I'm curious if P0430 will stay away now too. But with regard to this issue I'm rather pessimistic and will report again if necessary.The vehicle is a 2005 Jaguar XJR (MY 2006) with 230,000 km.
For those who want to know more, here is the long story. Please excuse any linguistic inaccuracies, I'm from Germany.
The symptoms only occurred with higher performance demands. Noticeably worse acceleration in general and from about 120km/h on, stronger acceleartion led to a cut of power. The check engine light stayed off (surprising).
I then bought an OBD2 reader (who is interested: iCarsoft LR V3.0, maybe an old school tool but the Jag and me, we are also old school).
I'm not a mechanic, so I can't guarantee that all of my thoughts make sense.
With the OBD2 reader I read a few parameter. Lambda values on both banks went up to 1.27 under acceleration (higher values are not displayed) which I found quite worrying. The engine then cut power. The fuel pressure was somewhere between 350 and 400 kpa, which seems to be a fairly normal value. But the MAF sensor also seemed to measure plausible values. When accelerating, the value went up to 40 (I forgot the unit).
I then unplugged the MAF sensor which provides a very easy way to check if the sensor is the problem. The engine then goes into emergency operation and enriches more. The engine performance was significantly better, no power-cuts and the lambda values went down to 0.83 when accelerating. So I installed a new MAF sensor and the problem seems to be fixed. The engine runs well and the lambda values go down to 0.83 when accelerating stongly.
Previously I had already checked the old MAF sensor and the intake between the MAF sensor and compressor for any visible damage and had cleaned the MAF sensor with no effect.
Welcome to the Jaguar Forums! It's great to have you with us!
Thank you for sharing your success with the MAFS replacement. I have also had success resolving P0171 and P0174 by replacing the MAFS, after smoke-testing the intake, crankcase breather and EVAP plumbing and resolving all leaks. The signal from the old MAFS was plausible, but replacing it cured the lean codes and significantly improved engine performance. Our vehicles are just getting to that age.
Hi Don,
thank you for the friendly welcome! I use the forum for quite some time now, to get information on various issues. Now it was time to sign in and post.
I stayed with the original part from Denso. 90€ plus shipping, pretty okay.
Update information: after about 2000km no check engine light came up so I guess the P0430 issue has also been solved by the new MAF-Sensor. I didn´t expect that because the code only refers to bank 2 but sometimes you just get lucky.
Update information: after about 2000km no check engine light came up so I guess the P0430 issue has also been solved by the new MAF-Sensor. I didn´t expect that because the code only refers to bank 2 but sometimes you just get lucky.
don’t jump the gun here. Every time I thought I cured my 0430 code it came back two weeks later or three weeks later or a month later it’s a very delicate code and it doesn’t run the test all the time and it just needs to be out just lightly for it to show. I can’t tell you how many times I thought I fixed the 0430 code in my car I need to find it came back month later.
I had same problem. I knew that if two banks were lean it has to be a leak. but After replacing all the O rings adding one to dipstick and finally a smoke test. No leaks. I changed the MAF sensor but not OEM Autozone. Code remains. Ordered a OEM one and problem has been gone for over a year.
These codes are triggered when un metered air enters. Either a leak or in my case a faulty sensor giving false readings.
I just fixed the bank one lean code (0171) by simply cleaning the MAF - the extra bonus is the car shifts alot better now. Pretty remarkable diffference.
I guess I should try cleaning my maf sensor. Does anybody know what reading I should get off my maf sensor at idle or at 2500 RPM? I just did some data recording the other night and I was getting about 4G/S at idle.
I guess I should try cleaning my maf sensor. Does anybody know what reading I should get off my maf sensor at idle or at 2500 RPM? I just did some data recording the other night and I was getting about 4G/S at idle.
A general rule of thumb is that at idle the MAFS should read in grams-per-second about the same as the engine displacement in liters (or a little higher), so your MAFS reading at idle is in the ballpark.
It's far more difficult to judge the MAFS reading at higher engine rpm. It helps if your scan tool has graphing/recording capability. Somewhere in the engine management system manuals is a chart showing typical MAFS readings at various engine speeds. Check Gus's website, jagrepair.com, for the engine management service training manual.
A general rule of thumb is that at idle the MAFS should read in grams-per-second about the same as the engine displacement in liters or a little higher, so your MAFS reading at idle is in the ballpark.
It's far more difficult to judge the MAFS reading at higher engine rpm. It helps if your scan tool has graphing/recording capability. Somewhere in the engine management system manuals is a chart showing typical MAFS readings at various engine speeds. Check Gus's website, jagrepair.com, for the engine management service training manual.
Cheers,
Don
thanks for that information I think I heard that somewhere else about 1 g/L. I was getting about 12 at 2300-2500 rpm so I’ll go check out the engine management manual. Thanks
don’t jump the gun here. Every time I thought I cured my 0430 code it came back two weeks later or three weeks later or a month later it’s a very delicate code and it doesn’t run the test all the time and it just needs to be out just lightly for it to show. I can’t tell you how many times I thought I fixed the 0430 code in my car I need to find it came back month later.
Yep, you were right. P0430 is back. Don´t know why it was gone so long. Maybe the cat just wanted to do me a favor for giving it a new OEM MAF-sensor. I guess if I would install a trailer hitch it would throw a piston at me.
Code P0174, P0171, P0101
