hmm... on some cars a dirty MAF shows as P0172/P0175 (rich not lean codes). Grrr...

 

Update:

While no more warning lights or messages have appeared on the dashboard, code P0171 reappeared this past weekend followed shortly by code P0174. Because my more thorough cleaning of the MAF sensor temporarily killed these codes for several days last week, I have to assume that the MAF sensor is gradually going belly-up after 108,000 miles. Found a new Denso MAF sensor on amazon.com for $62 and ordered it. Once it shows up we'll see if it fixes this issue once and for all. Stay tuned....

 

Do you mind sharing the part number?

According to this, Denso does not make an air flow meter for us:

Find My Part | DENSO Auto Parts

Air flow meter stuff is frustrating. New ones are very expensive, and refurb units are insanely cheap (down to $15 on eBay). I ordered one of the cheap ones recently, and it just did not work. Air Temperature was spot on, fuel trims were very low at idle (no air leaks?), but jumped way up while driving, telling me this part just did not fit. I returned it for a refund. I would love to hear there is a working new part for $60...

 

fmertz,

The part number I ordered from amazon.com is Denso 197-6030. Check your current MAF sensor. While the original part number is probably different, it should be stamped with the Denso logo....

There is a forum member here who determined that our XK8 Denso MAF sensors are shared amongst several Japanese car models. He ordered a Denso MAF sensor for a Mazda 6 from China for $16 with free shipping through ebay and is currently running it in his 2003 XK8 with no issues. Perhaps he will chime in here and provide more details....

Using your Denso parts search link above, when I select "Mass Air Flow Sensor" and then enter part no. 197-6030, it indeed shows up as valid. So I have my fingers crossed that this component will indeed resolve my issue....

What codes were you getting to cause you to order the cheapie sensor that did not work properly?

 

there are 2 different threads in the XK8/R section discussing alternates. One lists all vehicle makes and year that share the same MAF and the other references Mazda

I did a advanced search using key word "Denso MAF" and restricted it to the XK8/R section

https://www.jaguarforums.com/forum/x...cement-118214/


https://www.jaguarforums.com/forum/x...toyota-147115/

 

I also hope it fixes your problem, so I'll know what to order next.

I had no code, but the engine was acting sort of funny. I fully admit that I might be a victim of data perfectionism, but the intake air temp is returned as sort of high on this original sensor, even after a couple of deep cleaning. It is pretty systematically 8-10 deg F above ambient. When I read the fuel trims, they are low at idle, but higher than I want at higher rpm (in the teens). I think my AFM reads low, so the feedback mechanism is compensating for it with positive fuel trims. It is not high enough to trigger a code (above 25, I believe). As the trims are low at idle, I discounted the possibility of a simple air leak for now.

The cheapie sensor gave me near perfect air temp (within 1-2 deg F), but the trims were all over the place: long term in the high teens, and the short term going back and forth from -15 to +15 within a few sec. Engine was lumpy, took a lot more "gas" to get off the line, and was surging at constant speed. So I returned it, and put the original back.

Altogether, I would like to find a reliable new part at a decent price, so I hope this part you located works out.

 

As a point of reference, our local Jaguar dealership wants $228.50 for a new MAF sensor (part number C2S2670). Searching the net reveals multiple alternative sources for this same part number with a relatively wide range of prices from about $225 all the way down to just over $100. I hope my $62 Denso 197-6030 MAF sensor turns out to be compatible and will indeed cure my issue. I'll find out once it shows up in my mailbox....

 

Update:

The new Denso MAF sensor from amazon.com arrived last evening. It is an exact match to the original MAF sensor in design, shape, and fit. I installed it and took off on several drive cycles. Unfortunately, P0171 and P0174 returned on the second drive cycle. This morning I verified that my 2005 S-Type's original factory MAF sensor is indeed identical to my wife's XK8's original factory MAF sensor, even down to the same numbers stamped into the plastic (1X43-12B579-AB). So I swapped my S-Type's MAF sensor into my wife's XK8 and took off on several drive cycles. Again, P0171 and P0174 returned on the second drive cycle, and this time the "Restricted Performance" message appeared and disappeared a couple of times on the dash and the check engine icon illuminated and stayed on. So I think we can now rule out the MAF sensor as the cause of my issue....

I called my trusted local indie shop (Flying Circus English Cars in Durham) and relayed my experiences to them. They told me that given the P0171 and P0174 codes I consistently get, they would initially suspect the fuel filter, the air filter, or the spark plugs. I last changed the fuel filter and the air filter less than 18,000 miles ago when I performed the car's 90,000-mile service so while I cannot rule them out, I would be extremely surprised if either was the cause of my issue. Granted, the spark plugs are original factory plugs now at just over 108,000 miles but I know from more than a decade of previous experience that both NGK and Denso iridium plugs are the best in the world and typically do 150,000 to 200,000 miles with zero problems....

Flying Circus does not suspect my oxygen sensors because both P0171 and P0174 continue to be thrown together. They say that typically an oxygen sensor failure will throw one or the other but not both. They say it is extremely rare for the oxygen sensors on both banks to fail at the same time....

So I will allow the XK8's engine to cool down a bit and then have a look at the air filter (which I believe will still be clean) and the spark plugs (which I expect to still be pristine but perhaps I will be surprised). Flying Circus said that at 108,000-plus miles, they think my problem is probably originating from the original factory spark plugs....

Any additional input is welcome....

 

At this point, I feel you need more data. A cheap ELM327 with TorquePro (or equivalent on iPhone) would give you all the key parameters, like fuel trims (short and long term, from each side), air temp, air flow, fuel pressure, intake pressure, rpm, load, etc. This is a VERY inexpensive tool that nobody should be without. Check eBay.

Without seeing the fuel trim numbers, and how they behave with rpm, it is hard to recommend any next step.

If you are very bored, I suppose you could check the EGR pipe. It is behind and sort of below the throttle body, under a heat shield. It is a hard metal pipe with bellows that have been known to deteriorate over time, and allow air in.

Also, take the big intake pipe off (between the throttle body and the air box), and double check it for leaks. If put back incorrectly, it can rub on the hood liner and develop leaks.

Last, double check the o-ring at the base of the air flow meter. There have been report of ill-fitting o-rings before. You might have to compare and transfer the original one to the new sensor. Also, check that it does not get pinched because the sensor goes straight down, there is no twisting to put it nicely in place. This could be another air leak.

Best of luck, keep us posted.

 

fmertz,

Thanks for the feedback. I'll check the areas you indicate. In September 2012 I replaced the plastic accordion air duct that runs between the air box and the throttle body due to the accordion pleats cracking and opening up. I don't think it has had enough time to crack again but I will not know until I check. I've read about that EGR pipe but never checked it so now is probably the time to do so....

By the way, I'm going to leave my new $62 Denso MAF sensor from amazon.com in my S-Type for a few days and hopefully verify that it indeed functions properly. My guess is that if it works in my S-Type (with the 3.0 V6), it should work in our XK8s as well. We'll see....

 

Update:

I re-installed the car's original factory MAF sensor and noted that its O-ring is properly seated and tight. The air filter is still very clean as I expected it to be at less than 18,000 miles. The September 2012 plastic accordion air duct between the airbox and the throttle body looks good and is still completely intact. From what I can see and feel of the metal EGR pipe underneath the throttle body, it also looks good and feels intact. The various air hoses that I could see and feel with the airbox and air duct out of the way look to be properly attached as expected....

The factory-installed NGK IR IFR5N10 spark plugs now have more than 108,000 miles on them and while a couple of them had a bit more wear and build-up on their iridium tips than I would have expected, they still looked pretty good to me. Their tip residue was essentially tan in color and I assume that still means they have aged properly (as I was taught back in the 1970s, tan is good). No oil in the spark plug wells at all - they remain shiny and squeaky-clean. The plug tip gaps were all between .89 mm and 1.0 mm and I have not yet checked to see how that compares to what their gap should have been when they were new....

So maybe the car does indeed need new plugs. My Jaguar service manual for this XK8 calls for new plugs at 100,000 miles but as I mentioned before, I've had such good success running both NGK and Denso iridium plugs in other vehicles for well over 150,000 miles that I automatically decided to keep running these factory plugs back when I did the 100,000-mile service last year. I'm going to search for new NGK iridium plugs online, see what kind of deals are out there now, and then make a decision on whether to order a new set....

 

Question:

If my original factory spark plugs now at 108,000 miles are indeed the problem, wouldn't they be throwing misfire codes (P0300 through P0308) instead of bank 1 and bank 2 lean codes (P0171 and P0174)?

 

My sense is that spark is a heavily monitored parameter. Just open the book and check how many different codes can pop up for ignition-related problems. I feel that if your plugs were "bad", some code would pop up specifically for it.

What kind of gas (octane) do you run in this car?

 

It is my wife's car. She always fills up with 93 octane at our local BJ's Warehouse Club where we get a 10-cent per gallon discount using our BJ's MasterCard at the gas pumps....

 

To the extent that you would consider this a "no brand" gas, (thinking additives/cleaners, here), you might want to throw a can of injector cleaner. Probably not going to help...

 

I add a 20-ounce bottle of Chevron Techron at every oil & filter change / tire rotation I do on both of our Jaguars (6,000-mile intervals). I may do so now but like you, I do not expect it to help....

 

Change the plugs and see how it goes however, if you still have the codes then do a smoke test. If it is a good shop they can make a few checks with OBDII test equipment. Quit throwing parts at the car.

Gus
www.jagrepair.com

 

Gus,

I have only thrown one part at the car - a new Denso 197-6030 MAF sensor for $62. The good news is that it is now running perfectly in my 2005 S-Type, proving that it is indeed compatible with these cars. I'll eventually put it on my garage shelf because sooner or later, one of the Three Amigos (Rick {joycesjag}, Wayne {cjd777}, or me) will need it....

Earlier this afternoon I caved in and ordered 8 new NGK IR IFR5N10 iridium spark plugs from rockauto.com for a grand total of $76. They should be here on or before next Tuesday. I hope they indeed do the trick. Flying Circus believes they will. So does Wayne. We'll see....

 

If they're not sparking right then you get unburned fuel/air. That reads as air to an O2 sensor so you get lean codes. This is a great example of why really we should not call them lean codes! They are "excess O2" codes. (Commonly but not always due to an air leak, which can mean lean.) Steve Perry (xjrguy) put a good couple of lessons about this on the site (Gen Tech I think).

That said... yes you might get misfire codes but perhaps not till the plugs are very bad. And anyway it may not be the plugs, as it's hard to see more than one (i.e. at least 1 per bank since you have codes for each bank) going bad at the same time.

But.... they're due to be changed and I'd do them if only to rule them out. (I found they come out much easier with a pretty warm engine.)

 

As I reported earlier, two of the eight original spark plug tips were more worn and had more build-up than the other six did. One of these more worn plugs was on bank 1 and the other more worn plug was on bank 2. Perhaps that fact increases my chances of the new spark plugs resolving my issue....