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Your problem is different from Chris' in that his engine was running rich, and yours is running lean. The most common cause of P0171 and P0174 is unmetered air entering the system somewhere between the MAFS and the intake manifold gaskets. Here are the definition and possible causes from the DTC Summaries:
There are lots of places where air leaks can form on an XJR in the air intake, crankcase breathing system, EGR system, brake booster vacuum pipe, oil filler cap, etc. The fastest method for finding all the leaks is a smoke machine, which must be connected at various points to test the entire system. I usually start by removing the MAFS and sealing its port with duct tape. I then connect my smoke machine's large cone attachment to the main air intake pipe where it meets the air filter housing. I turn on the smoke machine and look for leaks around the various Helmholtz resonators molded into or ultrasonically welded to the main intake pipe. I also look for leaks where the aluminum intake pipe meets the throttle body and where the crankcase breather hoses and brake booster vacuum pipe meet the induction elbow below the throttle body. If you see any smoke leaking back there near the firewall, you may need to remove the windshield wipers, wiper cowl and false bulkhead to gain sufficient access to determine where exactly the leaks are.
Next I disconnect the corrugated part-load breather pipe from the air intake and inject smoke into the breather pipe to test its connection to the left cam cover and to test the cam cover gaskets and oil filler tube gasket(s). On normally-aspirated engines or later supercharged engines with variable valve timing, look for oil leaking from the VVT solenoid seals. If oil can get out, air can be sucked in. Replacing the seals is easy.
Then I disconnect the full-load breather pipe from the front of the right cam cover and inject smoke into the pipe. Look for leaks anywhere along the length of the breather pipe, and at its other end where it connects to the lower left rear side of the induction elbow.
Inject smoke into the right cam cover via the breather hose port to test the right cam cover gaskets and the crankcase vent/oil separator O-rings (the round part that looks like a PCV valve).
You may or may not find leaks at all of those joints, but it's a great idea to just replace every O-ring you encounter.
Cheers,
Don
Hi Don!
Thank you so much for your quick reply! I found the vacuum leak at the connection between the valve cover and the tube that goes to the are intake. I also replaced the spark plugs so the engine is running great now!
The bad news is that I believe I have a bad torque converter or transmission. The car drives pretty well and doesn’t slip but makes terrible vibrations and low frequency popping noises when under load around 2K rpm. This can also be heard and felt when you rev the engine to 2k rpm in park or neutral although it is much worse under load. Any ideas? I purchased the car with a load exhaust that masked everything so I guess there’s a reason I got a deal. lol. Now that it’s quiet, I can hear all of the problems.
The bad news is that I believe I have a bad torque converter or transmission. The car drives pretty well and doesn’t slip but makes terrible vibrations and low frequency popping noises when under load around 2K rpm. This can also be heard and felt when you rev the engine to 2k rpm in park or neutral although it is much worse under load. Any ideas?
Hi Cody,
Good work finding the leak!
One possible source of rpm-dependent vibrations is a bad motor mount. The motor mounts or engine mounts are filled with hydraulic fluid, and they are known to leak and fail. It's usually fairly easy to see that a mount has failed due to the oily liquid that has leaked out. The rear transmission mount has also been known to fail.
It's not terribly difficult to replace the motor mounts but you need a means of supporting the engine from above. Many of us use the inexpensive engine support bar from Harbor Freight Tools.
Your problem is different from Chris' in that his engine was running rich, and yours is running lean. The most common cause of P0171 and P0174 is unmetered air entering the system somewhere between the MAFS and the intake manifold gaskets. Here are the definition and possible causes from the DTC Summaries:
There are lots of places where air leaks can form on an XJR in the air intake, crankcase breathing system, EGR system, brake booster vacuum pipe, oil filler cap, etc. The fastest method for finding all the leaks is a smoke machine, which must be connected at various points to test the entire system. I usually start by removing the MAFS and sealing its port with duct tape. I then connect my smoke machine's large cone attachment to the main air intake pipe where it meets the air filter housing. I turn on the smoke machine and look for leaks around the various Helmholtz resonators molded into or ultrasonically welded to the main intake pipe. I also look for leaks where the aluminum intake pipe meets the throttle body and where the crankcase breather hoses and brake booster vacuum pipe meet the induction elbow below the throttle body. If you see any smoke leaking back there near the firewall, you may need to remove the windshield wipers, wiper cowl and false bulkhead to gain sufficient access to determine where exactly the leaks are.
Next I disconnect the corrugated part-load breather pipe from the air intake and inject smoke into the breather pipe to test its connection to the left cam cover and to test the cam cover gaskets and oil filler tube gasket(s). On normally-aspirated engines or later supercharged engines with variable valve timing, look for oil leaking from the VVT solenoid seals. If oil can get out, air can be sucked in. Replacing the seals is easy.
Then I disconnect the full-load breather pipe from the front of the right cam cover and inject smoke into the pipe. Look for leaks anywhere along the length of the breather pipe, and at its other end where it connects to the lower left rear side of the induction elbow.
Inject smoke into the right cam cover via the breather hose port to test the right cam cover gaskets and the crankcase vent/oil separator O-rings (the round part that looks like a PCV valve).
You may or may not find leaks at all of those joints, but it's a great idea to just replace every O-ring you encounter.
Cheers,
Don
Originally Posted by Don B
Hi Cody,
Good work finding the leak!
One possible source of rpm-dependent vibrations is a bad motor mount. The motor mounts or engine mounts are filled with hydraulic fluid, and they are known to leak and fail. It's usually fairly easy to see that a mount has failed due to the oily liquid that has leaked out. The rear transmission mount has also been known to fail.
Cheers,
Don
I just took the car on a drive and tested the engine mounts too. The mounts appear to be in good shape. No leaks from them and not much movement from the engine when holding the brakes and giving it gas at the same time in both drive and reverse.
It sounds like something that rotates is out of balance. It’s enough vibration to make plastic pieces in the car rattle. I know it can’t be anything beyond the transmission because it does it when revving the engine too. I listened to the engine and supercharger with a stethoscope and they sound fine. I think it has to be either the torque converter or transmission but I want to be sure before I tear it apart.
It’s most noticeable at 1400 to 1500 rpm, smooths out around 1800 and gets even worse than before at 2000. It happens at all rpms but is worse at those.
I should probably mention the noise and vibration gets more intense as you accelerate further into the rpm range. Whenever the transmission shifts, the noise and vibration disappears for a split second until the next gear engages. Also, sometimes on rare occasions the car will jerk when you let off the throttle after a hard acceleration.
Anyone have any advice before I take out the transmission? Also, if it is the torque converter that’s bad, do you guys have a recommendation for a good rebuilt or aftermarket torque converter for the ZF6HP26 transmission?
I just took the car on a drive and tested the engine mounts too. The mounts appear to be in good shape. No leaks from them and not much movement from the engine when holding the brakes and giving it gas at the same time in both drive and reverse.
It sounds like something that rotates is out of balance. It’s enough vibration to make plastic pieces in the car rattle. I know it can’t be anything beyond the transmission because it does it when revving the engine too. I listened to the engine and supercharger with a stethoscope and they sound fine. I think it has to be either the torque converter or transmission but I want to be sure before I tear it apart.
It’s most noticeable at 1400 to 1500 rpm, smooths out around 1800 and gets even worse than before at 2000. It happens at all rpms but is worse at those.
Hi Cody,
First of all, please visit your User Control Panel and Edit your Signature to add your Jaguar's year, model and engine details so they will appear in all of your posts and we won't have to scroll back to your first post to be reminded.
I don't recall hearing of a torque converter failure mode that vibrates as you describe. If the vibration occurs with the transmission in Park, then that would seem to rule out the transmission. If I recall correctly, the torque converter failure mode some early X350s suffered from was a hunting rpm at certain engine speeds, while driving the car. I think if you search "torque converter hunting" you may find some posts on this topic.
In the absence of misfire codes, I'm still leaning toward a motor mount or transmission mount. If you can get the car on a lift and run the engine up to 1,400 rpm, you may be able to witness movement somewhere.
If it's vibrating in park, and it's not a misfire, it's more like something is out of balance, I'd look at the crank pulley, more commonly known as a harmonic damper these days, however when they go they normally rattle like a big end has gone, it's a big old bit of kit on the Jag engine, and if it has been damaged and lost a chunk and gone off balance, it could well be your culprit, there are a few other pulleys that could also be out of balance, then if you go further back, the flywheel and torque convertor could also have gone out of balance, as they are factory balanced with weights, just like your wheels and tyres, but I'd def have a good rumage around the front of the engine before ripping off the transmission.
If on the other hand the vibration is when the car is moving, then I'd look at, the wheels/hubs, the prop shaft and the drive shafts.
Tranny is the last port of call, as it's the most expensive to remove or repair.
If it's a tricky fault, you should always work low to high, You don't want to go changing out a transmission first, only to find you still have the same fault after forking out a shed load of cash for that. hen having to start again.
Thanks guys! I’m going to do a little bit more diagnostic work before coming to a conclusion. I don’t have any misfire codes but I’m not entirely sure that’s not the problem. Maybe a partial misfire that’s not triggering the computer? I will report back with my findings. I appreciate all the help!
Thanks. I'm using Liqui P000041 Moly Ventil 1014 Ventil Sauber every 3000-5000km on my cars with great success.
On YouTube you can find a lot of videos showing how to clean the fuel injectors with Throttle Body Cleaner directly. For me, one part of the preventative service.
I finally diagnosed the vibrations after ruling out everything else for a verity of reasons. It was a very bad transmission mount. I could hardly believe what a difference it made. Smooth as silk now!
I purchased the mount from the local Jag dealership but it looks to be a new and improved part compared to the old one. Different design.
Now on to the new problem... P1338 code suddenly appeared the other day. The restricted performance light turns on for a few seconds sometimes a minute and then off for about the same amount of time. I have confirmed that I have fuel pressure and that both fuel pumps are working although that doesn’t mean they don’t have a problem. Otherwise, the car runs fine when restricted performance rev limiter doesn’t stop it.
I hope the transmission mount fix will help someone!
11-29-2020 | 11:03 AM
