4.2L engine......Getting the restricted performance quite often these days.
The plastic piping that goes along the top inside of the right side cam cover from the round valve to the back of the intake manifold; the connection at the intake manifold sure seems to be loose as it easily rotates.
I removed it and checked for leaks along the piping length, used a vacuum pump and the pipping was able to hold a vacuum.
Anyways, I have yet to find even the part number for this pipe or line.....can someone point me to where I can at least get the correct part number?
Now I have no idea if a new replacement is even available anymore.....so is there a way to use a length of hose and some type of clamp?

Thanks for any hints or leads.

Lannyl81

 

What codes are you getting with the restricted performance? Why do you believe its a vacuum leak?

 

I get the P0171: Bank 1 lean.
Engine seems to run normally, no missing or anything, so do not think it is a stuck fuel injector, weak coil, etc. Also doubt that the MAF is failing.
This is how I concluded it is a vacuum leak. Of course I could be wrong.
Do you have a suggestion?

 

Guess I am the only one with the 4.2L engine that has had the P0171: Too lean on Bank 1 error code.....
Anyways I am going to replace the six O rings on the breather hoses, see if that takes care of the problem. O rings on order, will update once I do the swap.

 

What are your short and long term fuel trims for both banks ?

If it were a breather leak I would expect both banks to give a lean reading

 

From experience, you likely have air leak(s). There are so many possible areas where leaks can develop that you are best off trying to procure/arrange for a smoke test, see where the smoke comes out and proceed with repairs from there.

The vacuum line to the fuel pressure sensor is a great option to inject the smoke into the intake.

The air flow meter may also be in play, but you normally get error codes on both banks when they fail. Other way of thinking is to just replace it, as our AFMs are common to several cars, and tend to be pretty cheap.

Best of luck, keep us posted.

 

Have you checked the underside of the accordion section of the lousy black plastic air intake tube for splits and cracks? It sits there on top of the engine and bakes in the heat, eventually getting brittle enough to start cracking and throwing various codes....

The best way to check it is to carefully remove the entire intake tube and slightly stretch that accordion section to see if broken gaps become visible anywhere around it....

 

I replaced the O rings on both breather tubes; made no difference. I still need to replace the O rings on the part breather or crankcase vent valve and will do that as soon as I find the correct size.
The first thing I checked was the air intake as I had to replace that a few years back due to it cracking. This time though the air intake is fine, no cracks, no splits, all good.

As previous posts have stated, the P0171 error code is for Bank 1 only and if the MAF had failed, should be both banks reporting lean.
Does someone have a manual that could post what the conditions are for the P0171 error code; would sure appreciate it.

There is no one around me that can do a smoke test.

Also have no software to show me the fuel trims or any live data.

 

A few additional common leak points that can trigger P0171 only are the two O-rings on the stem of the crankcase vent valve (the "PCV valve"), the Bank 1 VVT solenoid seal, camshaft cover gasket and spark plug boss seals. Also, a leak at the exhaust manifold ahead of the upstream O2S can cause the lean code as air is drawn in by venturi effect.

If you can see oil seeping out anywhere, air will be inhaled under engine vacuum.

And don't rule out the possibility that the engine is running lean in both banks, but the ECM is only triggering the code for Bank 1. As Stumpy mentioned, it's worth checking the trims in both banks.

Cheers,

Don

 

The condition for P0171/P0174 are that, based on the reading of the upstream/wideband O2 sensor in the exhaust, 25% or more fuel has been added to what the normal fuel table lists for a given load and rpm on that bank. IOW, there is so much air not measured by the air flow meter that the system has to add 25% more fuel than it normally would. More generally, that fuel correction is called a fuel trim. These can be read with a standard OBDII reader, they are not Jaguar/Land Rover specific.

For a smoke test, there are other options. There are devices for sale on eBay and other places. You can even make your own contraption by burning mineral oil with an old soldering iron. Some even do a cigarette cleverly setup on the cap of an empty oil container. Does not have to be sophisticated or even produce smoke at any significant pressure. Honestly, it is worth the effort, our intake system has so many opportunities for leaks it is not worth chasing them one by one. Another point is that the fuel trim are an indication of the sum total of all the air not measured, IOW there can be several leaks summing up to the need for 25% more fuel.

Check eBay or Amazon for a cheap ELM327 OBDII device and a mobile app. These devices are great for basic troubleshooting and the expense in minimal.

Best of luck, keep us posted.

 

I have an OBDII scanner, and I have paid to get the PIDS opened for my Chevrolet vehicles; but these do not work for the XK8. I have been using the app DashCmd for a couple of years to capture data such as long and short term fuel trims along with other parameters. However, they just do not offer PIDS for the XK8, sure be nice if they did.
What app lets you view fuel trims for an XK8?

I have seen videos in the past of homemade smoke generators; guess I had better go find those videos again.

I used some natural gas sealing tape around the O rings on the stem of the crankcase vent valve. Took it out for a short drive, just to see if the P0171 would return. It did not, although the drive may have been too short. Not going to run the engine like this for very long, just wanted to see if perhaps these O rings are the leak. Going to try one more time, then park it until the replacement O rings arrive next week

 

Quick update:
The 2nd test drive has good results, no CEL, no Restricted Performance either......so looking like it is the two O rings on the crankcase vent valve.
As I said above, will be next week before I receive the replacement O rings and know for sure....but I have hope!

Would still like to know what app shows the fuel trims for an XK8.

Thanks

 

I am an android person and use TorquePro, the paid version. You can basically "build" a screen that shows long and short term trims on each bank, load and rpm. Simplest is to start at idle where vacuum is highest and leaks would be a large fraction of the total air being pumped. Keep in mind there are separate trims by rpm and load, like in a matrix. I am not sure the size of the "box" for each trim.

All in all, and a bit arbitrarily, you need to bring those long term trims at or below 5%. Otherwise, the engine feel laggy/unresponsive. Low rpm going uphill (high load) seem to also bring ping-like sounds that are not good for anyone.

Best of luck, keep us posted.

 

Another update:
Thought I had it fixed....but nope. Wife took it out yesterday, made a trip of about 50 miles, mostly highway and no CEL, no restricted performance...all was good.
Then on the return trip, air temp about 105°F, AC on (of course) and going up a hill, she says she got a nice jolt, followed by the CEL and restricted performance yellow lite.
She made it back with no other issues, said it sure seemed to run just fine.
Pulled the code upon her return and same P0171.
Did notice that both cam covers had fresh oil under the VVT seals. I had replaced these seals about two - three years ago and I remember that I was not pleased with the fit of them (aftermarket).
I removed both of them, cleaned both seals and the cam covers, applied a small bead of RTV around the seal and put them back in. Just need to wait 24hrs now to see if perhaps this was the leak.

I am sure the crankcase vent valve was leaking as the CEL would come on after only a mile of driving. So, I did fix one leak.
Now I am beginning to wonder if the vent valve has failed somehow such that the vacuum is too high. There is no restriction to be cleaned-out using a drill bit on the left side cam cover like on the 4.0L engines.
There is always oil on the breather connections, especially the one at the rear of the intake. Nothing obvious to me with vent valve in looking at it; no cracks or anything. Not wanting to just replace it.
Any thoughts ???

Thanks again.

 

I have tried several aftermarket pairs of the VVT seals over the past decade or so. They sit there and bake in the engine bay, get hard and brittle, and seem to lose their grip every couple of years or so. They are cheap enough so that does not really bother me anymore. We have owned my wife's 2006 XK8 since early February 2012 and just from memory I believe it is currently on its 4th pair. I have the next new pair sitting on my garage shelf waiting its turn....

 

Yeah I agree....the VVT seals (aftermarket ones) are cheap enough to replace every couple of years. The applying RTV is a quick fix as we are currently down to one vehicle with a working AC since Summer is refusing to depart here in Southern AZ. I will be replacing the VVT seals anyways in the next week or so, she just needs a vehicle with a working AC.
The P0171 now only seems to appear after a run on the highway; is fine on surface streets....so far anyways.

 

Yeah I agree the VVT (aftermarket ones) seals are cheap enough and easy to replace every couple of years. I did the RTV as we currently are at one vehicle with a working AC; since Summer is not going away anytime soon here in Southern AZ....temps in high 90s and low 100s.
The P0171 code seems to only get set after a highway run; seems to be fine on the surface streets. Will see what happens the rest of the week while awaiting for new VVT seals to arrive.

 

Another update:
I was able to get my iPhone DashCmd app to show me fuel trims....and it appears I have been going down the wrong path.
The Bank 1 LTFT at idle is about +10% and stays steady; STFT is -1 to -2 and is also pretty steady.
Now when I increase the RPMs, Bank 1 LTFT goes up and up......I saw +17 at one point. Let off the throttle and LTFT goes back to about +10.
Looks like I have at least one bad fuel injector, probably dirty. These are originals and have 126k miles on them.

Question, is there somewhere to send them all out for cleaning?
Or.....is there someone known here that has a cleaned injector set for sale?
I did check RockAuto and $38 for re-man, $63 for new; each injector. Got to be another place....???

 

I forgot to mention in the above posting that the Bank 2 fuel trims were normal and did not change much with RPM.
Anyways....today's activities......I decided to swap the Bank 1 and Bank 2 fuel injectors. My thinking was that IF Bank 1 had a "bad" injector, then the lean condition would move to Bank 2.
So that is what I did this morning, got them all swapped around. I did wipe the end off with a paper towel but that is all the cleaning I did. I also checked the resistance for each one and they were within about 0.3 ohms....so all good there.
Took the XK8 for a drive later afternoon, both surface and a couple of miles of highway.....and...............nothing....no CEL, no restricted performance.....nothing!!......
Will drive it again tomorrow and then take a look at the fuel trims again.
The saga continues......

 

Well....that's interesting!!
Out driving and finally get the yellow lite, restricted performance, CEL.
Get home, read the codes, and now I have P0171 and P0174.
I had also cleaned the MAF (using the correct spray) before taking out on the test drive.
I can only view the fuel trims sitting still. But now Bank 2 is almost as high as Bank 1, 5-7 percentage points behind when increasing RPMs to 2000-2500; STFT for both are about the same, less than 10%. Bank 1 went to a high of 19.7%, with Bank 2 max at 14.5%.
I hope I just did not let the MAF dry thoroughly, causing both codes and fuel trims to go positive.
Will try again tomorrow