The local place who has done some simple jobs on my 04 xj8 put a crankcase full of synth blend in my car with 120K on it yesterday and my CEL immediately came on. I drove it back in there and they reset the code with a shrug of the shoulders basically refusing to acknowledge they could have done anything to make this happen. On a previous service they left the main air intake partially open to atmosphere causing CEL and a burned up MAF sensor. They apologized and made good on it. This time I found no signs of air leaks from any "service" they might have done. But the stick shows a bit higher than full. Could too much oil in the sump cause problem in the crankcase ventilation which seems to be tied in with overall air breathing path? I don't know whether to make them take out the excess as possible cause or just move on. Thank you.

 

What code has been set?

 

I woke up in the middle of the night realizing I had failed to mention it is the same ones I always get: 171 and 174 for too lean each bank. I used a wifi dongle with torque pro on my tablet to watch stuff while driving. Very dangerous, I know. LTF runs very high ~+18 on both banks all the time. STF fluctuates right around zero sometimes going + or - briefly. Timing is from 25 to 45 degrees advances almost all the time. AF ratio runs right around 14 + or - a few decimal points all the time. O2 sensors are all over the place and show heightened sensitivity to throttle action but are between 0.8 and 0.1. These values are about the same even after clearing the code and CEL off. When it pops back on, I see the same values on these parameters. THank you.

 

It's got nothing to do with an oil change.

 

If they drop when you rev then you've an air leak. Lots of posts about what to do next.

Be aware there are multiple codes containing 171 / 174 so you will find life easier if you use the full codes.

It _could_ be but need not be something knocked/damaged during an oil change but don't assume so.

 

Codes showing are 0174 lean mixture for one side and 0171 for the other side. When you say "they drop when you rev" do you mean the STFs? The O2 values track the pedal pressure very tightly but always return to some kind of homeostasis during smooth cruise.

 

When JagV8 suggests you use the full code, he means to include the letter prefix, which in your case is P for Powertrain, as in P0171 and P0174. There are other P codes, as well as B (Body) and C (Chassis) codes, with the numerical sequences 171 and/or 174, so it's important to include the P.

You can download the Diagnostic Trouble Code Summaries Guide at the link below:

Jaguar X350 DTC Summaries Guide

I think we are a bit confused because your original question was whether the oil change shop could have triggered the fault codes, but you seem to also say that you "always get" these same codes. So if you have had them in the past, was it simple timing that made you wonder if the oil change shop might have triggered them again?

Since the most common cause of these codes, when they appear together, is a leak in the air intake plumbing between the Mass Air Flow Sensor (MAFS) and the intake manifold gasket, it would be worth carefully inspecting the large black plastic air intake pipe that connects the air filter housing with the throttle body for loose or improperly positioned ends or hose clamps, and for any cracks or other damage that could allow air to enter the engine without having been metered by the MAFS.

Cheers,

Don

 

Yes I realize I am doing some conflating here and apologize. My first brush with these codes was on 02 X-type which turned out to have a cracked vacuum line to the brake booster. When the referenced codes first appeared on this car (months ago before this oil change) I aggressively taped up all hoses and fittings coming off the valve covers that make their way via PCV or other means to the air intake side PLUS I improved integrity of air filter box and MAF and everything before the motorized butterfly plate. This banished the codes until this oil change event. I can see no damage or failures in air path anywhere upstream of the butterfly motor plate. If I clear codes, I can drive 100 miles before they reappear. The LTFT numbers have been high ever since I began monitoring via dongle with no CEL.
Yes I am asking what are chances this is a coincidence when readings via torque-pro and dongle in real time are not different now with CEL on than they were before "servicing" and no CEL.

 

They take 2 warm ups to flag. A small leak commonly cannot be seen visually but is readily detectable. There are MANY threads about these you can just read!

 

Bottom line to your question Thomas is almost certainly coincidental, but, as Jag V8 already replied, not impossible. The filter is underneath. when the under scuttle is removed, there should be no vacuum lines near it. You don't even need to remove the vanity covers on top to fill the oil so little chance a vacuum line was disturbed. So unless some knucklehead attempted to pull the PCV to fill the oil...you'd need to go down the conspiracy line of thinking to link the two problems.

Even if a vacuum line was disturbed, your next step is to troubleshoot the codes following the recommended steps in the manual, most of which are covered ad nauseam in the forum if you search for P0171 and P0174. They aren't particularly difficult problem codes to resolve.