I think I’m looking at a supercharger and manifold removal.

I’m getting a P0171 (right bank lean) and restrictedperformance almost once a day. It only happensat fairly low speeds, and after I hit normal speeds (40 or so), the RP goesaway, but the CEL remains persistent unless I clear it. This used to happen less than once a month,but in the last few of weeks it has been happening much more frequently.

I’ve never received a P0174 (Left bank lean), so I’m led tobelieve I must have a leak downstream of the SC that only inhales at lower manifoldpressures with the throttle almost closed (i.e., at lower speeds / idle).

Is this reasoning sound? I wonder, because if it is due to lower MAP with the throttle barelyopen, I would think I’d also get the warning at highway speeds when I take my footoff the gas (I never do). When Ireplaced the plugs last month, they were a little on the white side, but not somuch as to cause any real concern, and all four were perfectly uniform.

I have a FF exhaust system with separate right and leftsides. The soot build up on the chrometips is light, and the same from left to right. However, while sitting at idle, the right side doesn’t seem as “puffy”as the left. It just might actually belean, but the TRIMS “should’ compensate for this – right? I don’t think it could be an upper O2 sensor,because then my right side exhaust would be sootier from the over rich condition.

Could there be another probable cause?

I’ll apologize in advance for not having done a Starting Fluid spray test, which could confirm the suspected leak, or checking my fuelTRIMS yet; I’m just poking around the brain trust here in advance for any likely causes other than the intake plumbling. I've read several related threads, but haven't found one specific to "just" P0171 or P0174 (not both) yet. I'll keep looking though.

Thanks in advance - you guys are GREAT!

 

OK, here are the fuel trims right after I pulled into the driveway:

Idle
Short 1: 7.8
Long 1: 19.5
Short 2: 0.0
Long 2: 10.2

2,500 RPM
Short 1: 7.0
Long 1: 19.8
Short 2: 2.3
Long 2: 10.9

So there obviously should be a leak somewhere right? Well, ..... Right after I checked the Trims, I sprayed starting fluid all over the place: The Supercharger output duct, down along both sides of the intercooler, both valve cover vents, the EGR valve and all over the intake tube from the MAF sensor to the throttle body. Guess what? Yup - no change in RPMs anywhere!

So, .... Back to the Brain Trust we go. You guys have any ideas?

If we rule out a leak and the O2 sensor, what's left?!

Doncha just love this stuff? - lol

 

After looking at the numbers for a while I realized that with the left Long Trim at ten, I might have an opportunity to drop them both a bit, so I cleaned my MAF. There may well be some sort of slight leak on the right side, but if I can drop both Trims even just 5 points, I may settle in below the P0171 threshold. I'll check the Trims again later.

I'm not sure why the right short Trim was so high. I'll let the engine idle a few minutes more next time and monitor more closely.

 

They don't drop when revved so not an air leak.

That leaves everything else

MAF, maybe. Ditto injectors, fuel delivery (changed the filter?), etc.

 

Thanks Jag. Agreed - it doesn't seem like a leak now. I cleaned the MAF last night (it "was" a little dirty) and was looking forward to a nice change this morning. However, the readings stayed pretty much the same ("AND" I received another 0171 & brief RP on the way to work). I even waited for while after parking to see if the idling short Trim 1 would re-baseline to zero and what effect that would have on the long Trim. Nada. In fact, short trim stabilized at around 5.7% and never went any lower. This might indicate reduced supply, but while driving to work the long Trim would actually drop to around 15% (from 19+%) and the short Trim would go negative from time to time. So I don't think it's a supply problem. Unless, ...... How would I check the Pressure Regulator?

All the spark plugs were uniform so I'm not really suspecting an injector problem unless all four were fouling uniformly as well. I also use about an ounce of MMO in every tank of gas (this has proven beneficial in every vehicle I used the stuff), so I feel pretty good that unless there are mechanical problems, my injectors should be in good nick.

The fuel filter only has 55K Miles (and 2.5 years) on it.

The left side Trims responded normally though - the Short baselined near zero, but I'd love to find out why the Long Trim is a little high at around 10%.

What might an ECM reset do? I read of it being recommended for a myriad of problems, but I've been hesitant to completely power down the car though; I even hook-up a motorcycle battery or charger to keep the system powered during battery changes.

 

Shot in the dark: Some of the nastiest air leaks I have heard of are in the elbow/bellows of air ducts. A crack in one of those may only open when torque is applied to the engine and it rocks on the mounts. At idle, or with less torque, it may seal back up. Just a thought. AFAIK, XK8s are subject to this as the plastic intake can rub on the underside of the hood and eventually leak. I have no direct experience with this, but I was told the dealer I bought the car from had to replace it. Not sure of the intake routing on an XKR, though, could be completely different.

 

Thanks FMERTZ. Yeh - A good visual inspection of the plastic duct about a month ago turned up a crack in one of "sound tubes" on it. I patched that and didn't have a 0171 for weeks until just recently. I need to take a closer look at that duct. Maybe come up with some way to smoke check it.

The XK8 and XKR ducts are fairly similar. Their routing is identical, but I believe the R has more sound tubes sticking out of it and might be a larger diameter.

 

Scardini1,
You might try tracking the voltage from the O2 sensors and see how they compare side to side. Lean condition should be detected by the difference between up stream and down stream on each side. One of the sensors might be giving bad data but not severe enough to cause a sensor fault warning.

 

Thanks Craig. Good idea. The upstream O2 sensors are "only" 175,000 old. :-)

I need to figure out which acronyms on my tester are the O2 voltages (they're a bit cryptic). Whatever's going on is getting worse fast. I had three 0171 & RPs yesterday. I drove with the tester hooked up and the Trims all drop whenever I press on the gas, no matter how slightly. Still sounds sort of like a leak. I'm scratching my head over why the Right short Trim won't drop to zero (unless the long Trim is limited to 20%).

Obviously, The situation is easy to deal with so long as the RP disappears at normal speeds, but I'm concerned that soon it will affect normal driving as well, and of course I don't want to subject the engine to over-lean mixtures.

....sigh.... And I had gotten so used to "not" having my CEL lit all the time - lol

 

I guess I should add that other than the CEL & brief RPs, the car is running fabulously. This is such a frustration.

 

I'm starting to get worried. I spent over an hour attempting every diagnosis I could think of. I smoke checked the intake duct (no leaks), I checked both breather tubes (all clear; o-rings are fine); I used starting fluid and propane all over the place (no changes noted on the scan numbers), and I cleaned out the throttle body as best I could. I did an ECM rest to re-baseline the trims. They quickly returned to previous values.

The idle trim numbers seem worse now too. The long 1 is steady at 19.5 (which seems to be its max) and short one is hovering in the mid-teens now, but will hit 19.5 at times as well. Long 1 to is up as well; steady at about 13, but at least short 2 is oscillating back and forth through zero.

I should add that I tried to check O2 sensor voltages, however I'm not sure the scanner is looking at the upper sensors. The scanner lists only B1S2 and B2S2 (S2 possibily meaning lower sensors?)for voltage read out . Sometimes the voltages are hovering around 4.5v (good); other times the B2S2 may drop to less than .1v. Of course Bank 2 isn't my main focus (sigh). I may resign myself to replacing them just out of desperation.

And the car continues to drive beautifully. What's left to check? Even if it was a filter or pump problem, that wouldn't explain the discrepancy between left and right banks. Can my fuel pump fail slowly without affecting driveability? If my O2 sensors were going wouldn't the car be actually running rich (which it isn't)?

Any and all help is sooooo appreciated.

 

Check the life expectancy of these sensors. My recollection is that they should be replaced every 125k Miles.

Not to say it is easy, but what happens if you swap these sensors, left to right? Does the problem move as well?

 

Interesting idea fmerz. It's a real pain to get them out though. I have the Nameless Cats - I had to take the Cats out in order to put in new lower sensors. However, with 175,000 miles on the upper sensors, I think that if I go through the trouble to get them out, I'll just replace them outright.

I still think it must be something else though. If it was the O2 sensors, I'm sure my actual mixtures would be off. I just took another look at the recently removed spark plugs - they are all uniform and a nice light grey color. I was quite pleased with their appearance when they came out.

 

Unless looking for an air leak by spraying small amounts of burnable gas (e.g. propane), STFT s can probably be ignored. If LTFT(s) drop from 19-ish on revving to 2500rpm or so then you 99% do have an air leak.

STFT tend to go crazy if you spray at a leak.

 

OK, .... Replacing the valley hoses was the next major project to be tackled, but I had been putting it off until one of the hoses sprang a leak last week. It's a major job on the XKR and I'm fairly religious about replacing every consumable item I touch in the process of a project. So while about $500 worth of hoses, seals and gaskets is on their way to me I started the disassembly.

Bad news: One of the bellows on my EGR tube (from the manifold to the EGR valve) was torn open almost all the way around.

Good news: This would explain not only the overall high LTFTs at idle/low throttle settings, but also the disparity between the left and right LTFTs.

Bad news: These things cost TWO HUNDRED DOLLARS!!!

You have GOT to be s**ting me! (....... groan).

After checking many sources, it seems that our Sponsor, SNG Barratt, has them at the lowest price so far: about $200 delivered.

If anyone knows a significantly more affordable source, please let me know. I was not planning to have this project heading toward $1K. Now I wish I hadn't ordered so many discretionary parts.

Despite it all, I do love this car though.

 

Here's a pic of the crack. It actually goes 3/4 of the way around the pipe. Just out of curiosity, I'm going to take it to a local machine shop that's done some "creative" work for me in the past. I'll see what they think about welding it up. At 200 bucks for a replacement, it's certainly worth asking the question.


Another idea, which I think will work great, is to cut the bellows out completely and replace it with Hi-Temp hose. I need to investigate this a bit.

 

Yikes, this isn't the first post on a EGR pipe that produced holes/leaks.
Makes me worry.. good luck on a replacement
Also I think there maybe gaskets from the previous post I read, do a search.

 

Thanks JAM. For future reference, the symptoms were: elevated idle LTFTs on both banks with the right bank being higher. Diagnostic indicators do point to a vacuum leak (i.e., the LTFTs drop when the throttle opens), but you'll go nuts trying to find it. RP may come and go when idling or in heavy traffic, but the car will throw no codes on the open road. The pipe failure could also explain why the P0171 is so much more common than the P0172.

As I kinda expected, the shop's welding expert said the bellow metal was too thin to weld up, but that if I could find a replacement bellow (with cuffs on the ends), he could make the swap. That's a dead end, of course.

Another idea that I'm going to pursue is to try some Quik-Steel epoxy putty. I think I can shape a collar that may be structurally sound, but the material is only good to 500 degrees F. I'd be much more confident with a 1,000. The pipe is pretty easy to get to, even with the engine assembled. I'll shape the epoxy collar with the pipe in place so as to relieve as much stress as possible and see how well it holds up after I put the car back on the road.

 

I think it might be possible to braze the bellows, surprised they didn't try it. But I suppose brazing with oxy-acetylene is too old school for todays shops.

 

Or... here's a thought, look in the classifieds for someone parting out a car?? Oh yeah that's right, I am!! An entire car, all the parts. I could look for this pipe, check its condition and sell it to you for Oh... I don't know, $25 bucks??
I just don't get it!! This happens over and over. I literally have to search the posts to find someone needing a part and then contact them to get any of this stuff sold!!
I have been on many other forums dealing with cars, mostly American muscle cars, and people needing parts contact me!! What a concept.
I am not taking jabs at anyone in particular, it just surprises me how Jag guys like to spend waaay too much money for a part going on a car that isn't worth the ground it's sitting on!!! I guess because it says JAGUAR on it!? Don't get me wrong, I love the car, bought mine site unseen and got screwed by a certain dealer / person in N Carolina. That's a whole other story!! Anyway, I have mine for sale on this forum, for what I consider to be a 'fair' price and have had absolutely '0' response!!?? Only reason I am selling is because honestly at 6' 5" 240lbs, I just don't fit comfortably in the thing. With the top down I look like Herman Munster looking over the windshield. Anyway, enough ranting, I will have to look but I probably have this tube. I know I haven't sold it to anyone. Along with a lot of other parts. All it takes is an email and I am pretty quick getting back to everyone!!
Good luck!!