I am getting a pronounced vibration under load. It is most evident at about 70 mph when I try to take a hill or accelerate from that speed. It manifests itself both as a vibration through the body and roughness from the engine.
I have no fault lights, the engine and transmission mounts are new. The car seems to run and drive fine otherwise.
I have superficially inspected the driveshaft and the rubber joints only show minor surface cracking. Nothing catastrophic is evident.
Any thoughts?

Also, happy holidays to all.

 

First place I would look is coils and LTFT and STFT

 

Coils are new. Should I check fuel trim at speed?

 

Well, if you have new coils, my next move would be to scan for all codes, even though you may not have an illuminated CEL.

 

No codes.

Bank 1 - STFT: 1.1%; LTFT: 11.72%
Bank 2 - STFT: 1.6%; LTFT: 9.38 %

These readings are at idle and at operating temperature.

 

What are you using to pull codes? And when was the last time you have had an injector cleaning and/or fuel filter replacement?

 

I have a OBD II reader on my computer that interfaces with the diagnostic port under the dash.
Fuel filter is fairly new (less than 6 months). Injectors have not been cleaned. I have run a couple of cans of BG 44 through a while back.
The car runs reasonably well and does not necessarily lack power during this event. It will power through the rough patch and if you get the revs higher or are at a different speed the event is less prevalent.
I was wondering what the likelihood of a driveshaft/flex coupling issue?

 

LTFTs are high. If you check again that they are and then rev to 2500 or so what do they do?

 

If it were issues with the driveline, it would present itself pretty much every time, all the time. With fuel trims attempting to richen the mixture by as much as it is, you could easily have lean misfire under load. Without using SDD, you may not see some codes, or flight recorder info. I can say it is more than likely not far from setting lean code at the LTFT you have. At this point I would check for any vacuum leaks and insure hoses are tight and seated, wash the MAF, and do a battery reset and then drive the vehicle again and review trims after 50 or so miles. 44K, while a good product, will not always do what an injector clean will do, and if after the 50 or so miles LTFT is still as high as it is now, I would suggest an injector cleaning. SDD can also help you diagnose live data to help you understand what is going on.

 

Thanks again for the input.

Bank 1 - STFT: 7.03%: LTFT: 2.34%
Bank 2 - STFT: 4.69%; LTFT: 1.56%

This was at operation temperature and about 2500 rpm.

Idle was:

Bank 1 - STFT: -0.78%; LTFT: 14.06%
Bank 2 - STFT: 1.56%; LTFT: 8.59%

Okay, it set some misfire codes recently. P1313, P1316, and P0301,0303 and 0305. Just Bank One cylinders. I cleared the codes and they did not immediately re-appear.

 

You really need SDD to help you diagnose. Your problems deal with both sides actually, it's just not severe enough on bank 2 to set codes just yet. You are going to cause catalyst damage if you continue.

Note regarding misfire monitor DTCs:

If, on the first trip, the misfire is severe enough to cause excess exhaust emission, the individual cylinder DTC plus DTC P1316 will be logged. The CHECK ENGINE MIL will not be activated. If the fault reoccurs on the second trip, the individual cylinder DTC plus DTC P1316 will be flagged, and the CHECK ENGINE MIL will be activated.

If, on the first trip, the misfire is severe enough to cause catalyst damage (more severe than excess exhaust emission), the CHECK ENGINE MIL will flash while the fault is present and the individual cylinder DTC plus DTC P1313 (bank 1), DTC P1314 (bank 2) will be logged. When the fault is no longer present the MIL will be deactivated. If the fault reoccurs on the second trip, the CHECK ENGINE MIL will flash while the fault is present and the individual cylinder DTC plus DTC P1313 (bank 1), DTC P1314 (bank 2) will be flagged. When the fault is no longer present the CHECK ENGINE MIL will be activated.

You can review your code information here;

 

First, let me thank you for your assistance. It did not go unappreciated nor neglected. It took a while but I purchased a fuel injector cleaning kit (Mitivac) and tried it yesterday. The trim numbers did come down in my first short drive.
I am going to drive down to the local Jaguar club event tonight and will see how she does on the highway. I will have more quantitative information after that.

Best and again, thanks.

 

For what its worth, I once had a similar roughness at highway speeds and it turned out to be my transmission mount.

 

I had the same problem. The rubber around my driveshaft was cracked. There was enough play to where I could wiggle it around by hand. I replaced the shaft and the trans mount and its been very smooth ever since.