I am fairly sure this one hasn't been covered before or at least I can't find anything on it.
A couple of weeks ago I did what has turned out to be something stupid, I took the car through some deep(ish) water, now it wasn't crazy deep maybe 4 or 5 inches I think but since going through the car has decided to start surging. somewhere around 1500 to 2000 rpm, it's quite pronounced and makes the Jag pretty uncomfortable to drive, there are no fault codes showing although the fuel trim levels seem to vary a lot between banks. I'm not familiar with what the fuel trims are but I would assume that the readings should be similar between banks.
Question is, What could have been disturbed by the water to cause this? it may be a coincidance but I think it unlikely. the engine pulls just fine and you can drive through the surging but I would be grateful of any suggestions I can try. !

 

Does it surge when the engine is hot?

 

Yes it does, in fact it is much worse when its hot, running cold is almost normal.

 

Seems to be a very unusual fault.

I can only suggest that you check the fuel pressure with the engine running.

There is schrader valve on the end of one injector rail (with a blue cap).

The valve is the same as that on a tyre if you don't know.

 

Thanks for that, yes it is unusual, it has been suggested that it may be the fuel pump, I am getting that checked out but I am not that hopeful because of the specific range of the problem.

 

Just thinking that water could have got into the transmission connector, and false data is passing to the ECU from the TCM which is inside the transmission.

 

Thanks, I will ask them to take a look at that also.