Having just replaced the oil pressure switch by removing the intake to gain access, after refitting the intake with new gasket, engine stared fine a tiny bit erratic at idle not too concerned with, however from the next day the engine stared getting worse even though the revs are fluctuating just above 800 to just above 750. As of today a week later from the work done the engine sounds slightly rougher and the check engine light came on, fuel fail 44 reported. Plus I also feel the car is using too much fuel.

Has anyone have any ideas on a solution

Regards

 

Try replacing the lamba probe.

 

The labda sensor (bosch) is not yet 2 years old, and the car was fine before the work was done.

After a battery reset the vcm is showing no error and no check engine light but still idling rough

 

Look for a vacuum leak around the intake. Vacuum leaks can cause ECM to compensate by running rich

 

If it was fine before, you have to assume its something you did. I really like using an automotive stethoscope. With just the hose end run it over the intake and all the hoses listening for a small vacuum leak.

 

There is a valve on the back of the AIR injection pump which is vacuum activated. Its a 1/8 hose, could you have left that off? (I would have missed it I wasnt paying attention).

 

Where is the location of the AIR injection pump hose?

 

Why did you take off the intake manifold in the first place to replace the oil pressure switch/sender.?
It can accessed by a long socket system or a crows foot spanner.
I know it is in a buggar of a spot but using the right tools makes it easy.
My first XJ40 came really cheap because of a massive oil leak which turned out the sender had failed and was the source of the leak.
Took 20 minutes and fifty A$ bucks for a new sender to fix,

 

Depends on the model year. Not so easy on late model in my experience - and of course whether a sender or a sensor is fitted.

Larry

 

In my experience, on most North American LHD XJ40s, access to the oil pressure sender is so obstructed from both above and below that it really is easier to disconnect the intake manifold and tie it back out of the way, especially if it's your first time dealing with the sender. If you've done it before, you can do it blind, by feel, but it's no fun.

However, on an X300 it's easy to access from below, especially with the oil filter removed, because there are fewer obstructions.

Cheers,

Don

 

The XJ40 I referred to was a 1994 model ie the last of the series with battery in the trunk etc. however it was a right hand drive.
Looking at a left hand drive I must apologise because I can see what a horror job it is with extremely limited access to the area.
Cheers

 

I replaced the one on my 94 without removing the intake but I do have a pretty extensive tool set with lots of extensions and wobbles so it is doable for me.

 

Going back a bit, the air injection pump is right there in your way on the left side and the valve I was referring to is only a couple of inches of tubing off the back of it.