As a result of trying to cure an intermittent high idle on my 96 4.0l x300, I am becoming more confused by the list and various names of the potential parts which may or may not contribute to the problem. So, apart from possible fixes, I would like to be absolutely clear in my mind as to what I am dealing with. Incidentally, mine is an (Irish) European car, so it would help if the terminology used applied to this particular market.

1; Crank position sensor/s. Located on the flywheel housing and somewhere else beneath the engine?

2;Throttle position sensor. Is this mounted on the actual throttle body? If so, what is the device at the front of the engine, cylindrical and roughly where a distributor might have sat in the past?

3; Idle speed control valve, also known as idle speed stepper motor? Is this located on the throttle body? Small cylindrical device with a plug/wires fitted to the top. Held in place by two small screws.

4; Throttle pentiometer sensor? What and where is this or is the same thing as 2 above.

Any other relevant components that I am missing that might be relevant in this regard.

Many thanks

 

Great thread. I'm in need of the same information. Hope Mototcarman chimes in.

 

Here you go from downunder, NOT Irish, but close.

1) CAS (crank angle sensor) mounted on the timing cover, LH side at about 10 o'clock looking at the front. NOTHING on the flywheel on an AJ16.

2) TPS (throttle position sensor) mounted on the underside of the throttle body. Oil filter needs to come off to get at it.

2A) That whizzy thing living where a distributor used to, is in fact the cam angle sensor, and is used to time/fire the fuel injection sequentially.

3) YES.

4) Same as 2 above.

ENJOY.

 

Further to the above, I just noticed a post regarding an EGR Valve. Maybe this could be aded to the above with a view to expanding and explaining same? A stickie perhaps? It's just that there seems to be a myriad of possible causes for a single issue, that knowing what exactly we're dealing with can only help.

 

Great stuff, many thanks for that!

 

I think the EGR valve was fitted on all US spec 4.0L naturally aspirated X300s, but only 96MY and 97MY US spec XJR6. I don't think it was ever fitted to any European spec X300s (NA or SC), though there might be a few specific countries in Europe that had this engine spec.

On naturally aspirated AJ16 engines the EGR valve is mounted on the top of the inlet manifold between runners 3 and 4. On the XJR6 it was fitted at the rear of the exhaust manifold. The valve is black and cylindrical about 4" long and 2" diameter.

On high mileage cars the valve can stick in one position due to carbon deposits. This can lead to exhaust gas recirculation (EGR) at low loads when the valve would normally be shut, and this in turn can lead to poor combustion and misfires.

 

The EGR valve is that black thing mounted between the throttle body and the manifold with the electrical connection.