Greetings. Been a while since I posted anything here but now I have a reason.

Got the Restricted Performance warning yesterday on my 2003 XKR. Quick check with Torque app showed P0171 fault code (Fuel Trim too lean, Bank 1) and the engine sounded a bit rattly (nothing too bad).

As suggested elsewhere here I cleaned the MAF sensor and all the seals from the air filter box to the throttle body. Didn't see any visible cracks or holes on the tubing. The engine immediately sounded a lot better (=normal) after this so I cleared the fault code and took her for a spin. No problems so far but was wondering if there's anything else I should keep an eye on?

Thanks!

 

If you have TorquePro already, keep an eye on the long term fuel trims (LTFT), especially at idle. The code comes on if the LTFT goes above 25, I believe. The fact that your code is not coming back (remember this is a 2 trip code I believe) does not mean your LTFT are great. They should technically be zero, but I suppose low single digit is fine on an older car. If your LTFT are in the teens and higher, you need to go hunt for all possibilities of air leaks:

All the vacuum hoses around the head have o-rings. Change them.

If not done before, replace the hard oily leaking VVT seals.

The hard pipe for EGR has bellows that crack.

Etc, etc.

Have a look at the numbers, especially that there is a LTFT by bank, so you have something to go by.

Air flow meter have gone down in price very significantly. Consider just throwing in a new one.

I am going through a cleanup like this on my ow car, and it is great fun to replace a couple of o-rings, and see LTFT in the high single digits go down under corrective negative short term fuel trims. Its the "gamification" of car maintenance, if you will.

Best of luck, keep us posted.

 

Thanks a lot for your answer. I indeed have Torque Pro but I haven't really used it that much. Will look for the LTFT and keep an eye on them.

Cheers,
Kari

 

Possible causes:

• Contaminated fuel injectors
or see below

 

So I haven't really had time to do anything more on my car but I took her for a 10-15min spin and took the readings in the above screen shot. The short term trims stabilizez around zero but the long term ones remained higher. My question is how long is the long term? I've only driven the car twice for about 15mins since I cleaned the MAF etc. Should I give it a few more runs before jumping to any conclusions?

 

You now need to work through the possible causes on the right hand column of the table I put up - above.

 

First, you might want to swap your gauges left to right. Bank 1 is passenger side on a US car. Makes it more obvious to match the screen to the engine from the driver's seat.

I believe long term trims are updated from the average short term trims every few minutes (I seem to remember 2 min), so not very long. Trims are a 3D landscape, if you will, where the trim value is the height, and RPM and Load the other 2 dimensions, so it is not just one number.

On the face of it, you have air leaks mostly on bank 1 (high LTFT at idle). I believe the code triggers at 25%.

Best of luck, keep us posted.

 

Thank you all! Most helpful. I will take a look when I get a moment.

 

Mine was the VVT seals easy fix.

 

So I'm gearing up to do whatever I can myself out in the court yard with only hand tools available to me. I am able to lift the car a little bit with a jack and put it on axle stands but it's pretty tight to get under there and do anything useful in there. Do you think all of these are DIY jobs without the need of shop air:


Replace air filter
Replace MAF sensor
Replace camshaft cover gaskets
Replace spark plugs and their seals
Replace VVT seals
Replace any O-ring I take out

Any other DIYable jobs I could do while I'm at it?

Regarding the O-rings, does anyone have information what possible sizes I'd need?

Thanks,
Kari

 

So I finally got to actually doing something proper about this. I'm starting with the RH side where the LTFT constantly showed elevated trims. While stripping everything out of the way in order to replace the cam cover gaskets and vvt seals among other things I accidentally snapped the hose going from the PCV valve into the TB elbow. It seemed to be very brittle and almost snapped by just looking at it. Maybe this was leaking already and was causing the problem in the first place? I'll post a photo later...

I managed to get JTIS working on my Windows 8.1 but it's a little clunky to use imho. Can I somehow use it to find part numbers? If not then can some one give me either the part number of the hose or a better way to identify the parts and they numbers? Failing to find a new part, has anyone attempted to fix these reliably somehow?


EDIT: Here's a couple of photos. How is that hose supposed to come off from the TB?




Snapped PCV hose.



How is this supposed to come off?

 

Got her back together again after doing the following:

- Replace Bank 1 cam cover gaskets + retaining bolts and grommets
- Replace PCV valve
- Repair broken breather hose from PCV valve to TB
- Replace Bank 1 spark plugs
- Clean MAF sensor and replace O-ring
- Replace air filter
- Replaced oil filler cap with new
- Replaced oil dipstick with new
- Replace breather hose O-rings

While I was at it I tried to clean everything I touched as clean as I could get them.

After doing an ECM reset and driving the car for several hours in varying driving conditions the long term fuel trim on Bank 1 which was about +18 at idle before dropped to about +13.3. Slight improvement but I'd like to get this down more. How can I diagnose this a bit better and what would you recommend to check or even replace just as a preventative measure?

Time for a smoke test perhaps?

 

VVT seals? Known to leak. Cheap, and super easy to replace. Typically leak oil, meaning it probably leaks air in, too.

Now that you have numbers to gauge your progress, you have transformed chasing down these air leaks into a video game...

 

Feeling a little stupid here... Does my 2003 XKR actually have vvt? See picture below. The gasket kit that was supposed to be for my car did come with two new vvt seals but I just could not tell where they should go...

 

You are right, my mistake. No VVT on XKRs.

 

Did a home made smoke test today with the small fog machine I have. I've never done anything like this before but having seen a couple of youtube videos I thought I'd give it a go:

- Disconnected the air intake duct from the filter box and sealed it as good as I could
- Made sure the TB stayed open by jamming it with a soft piece of rubber hose making sure I didn't scratch any of the surfaces there.
- Installed the air intake duct back on the TB
- Disconnected the part load breather from above the TB and sealed the hose as good as I could
- Inserted a silicone tube to where the part load breather usually goes on the air intake duct and injected the fog from there

After a while I didn't see any fog coming out of anywhere so I thought I'd "pressurize" the system a little by blowing into the silicone tube. The only places I saw a little fog coming out was my temporary seals.

Since changing the gaskets and o-rings etc (see previous post) did not have a massive effect I'm beginning to think this might not be a vacuum leak after all. The spark plugs I replaced were quite dirty so I'm thinking the fuel injectors are probably pretty dirty as well. I'm planning on replacing the fuel filter and then running some BG44K cleaner through the system.

Any other ideas?

Just out of curiosity is it a massive job to replace the fuel injectors?

 

So you have LTFT1 at 18 or 13 or so at idle? But what is it if you then rev to 2500 or so and let it settle a bit?

 

Yes, LTFT1 used to creep up to about +18 before I did anything. After done what I've described earlier it's about +8 when the engine has just about reached normal operating temperature. From there it creeps up very slowly (within 30 minutes or so) up to about +13 the hotter the entire system becomes. So there probably was some vacuum leaks which I managed to improve a little bit.

The LTFT1 does drop down to about +6..8 when I rev it up to about 2500 rpm and let it settle. I know traditionally this is considered to be a sign of a vacuum leak. But here's an interesting bit that I just discovered today. When the engine is cold the downstream O2 sensor gives me readings. After a while when the system heats up the sensor goes to 0 volts and stays there.

Could it be the catalytic converter has gone bad? The sensor gives a reading while using it's internal heater and then when that drops off in closed loop, the cat is not heating up enough for the sensor to give out anything?