My XJR is being weirder than usual. I have a number of electrical oddities that make me think the ECU is bad. First, its in limp mode, limited to 3k rpm. The idle is occasionally very high, other times pretty normal. The little dash cluster screen mpg is giving me absurdly optimistic numbers. Etc...

I have previously cleaned the grounds in the engine bay, and today I visually inspected the ecu for any water damage and it looks clean and dry. Is it possible to reflash these or do I have to find a good used one?

 

The supercharged engine has a 2nd fuel pump controlled by the ECU that does not come on until a certain RPM

You can jumper the second fuel pump to see if it works

this would be socket 3 to 5 located fwd of the car battery

To operate the vehicle with it Jumper'd as you would have 2 fuel pumps running in the engine starting sequence is questionable and may over fuel it , the fuel pressure regulator may no be able to bypass enough if the injectors are not consuming a lot of fuel and you would end up with a higher then designed regulated fuel pressure ( 43 psi )

 

What DTCs (if any) are logged in the ECM?

Any RESTRICTED PERFORMANCE will leave codes.

 

There's no codes for engine or transmission. Today I started pulling the intake apart. Already found one torn rubber elbow and a snapped bolt that was probably causing a second leak as well. The entire intake past the supercharger is soaked with oil and sludge.

 

I don't have the supercharged version but one thing common to them both is an ineffective air ail / separator located inside the valve cover for the breather gasses going back through your intake

On yours you have the impellor bearings that have a certain service life from reading others

When I got mine, the residue was on past fwd of the butterfly and on to the inlet air temp sensor

You may have to clean both the mass air flow sensor and the inlet air temp sensor as the sensor values may be off throwing off your engine regulation with no codes

You have a different MAF sensor part # specific to the supercharged version

There is a TSB on a better air / oil separator you can ponder for the future

03.1-15 (jagrepair.com)

Other then the TSB there is other air / oil separator options but for now you just need to clean the sensors

Your supercharged version has a history of the valve seats fouling and a good hard drive helps

What are the electrical oddities you are observing as that's my jam ?

Your MAF sensor on the middle wire ( color Green / Pink ) will read 1.2 volts DC at the correct idle speed ( it has to remain plugged in )

Your throttle position sensor on the middle wire ( color Green / Yellow) should read 0.60 volts DC at the idle stop

You can test this with the engine not running with the key in the run position

It should climb smoothly as you rotate the throttle butterfly by hand very very slowly

It can also be tested at the ECU connector between socket Red 7 and Red 12 but you will be looking for smooth resistance

See page 55 and 90 , not sure where your IAT sensor is located

www.jagrepair.com/images/Training Guides/801S - 2000.pdf

 

I do not know if the ECMs are the same EXCEPT for the PROMS for each model and market.

You can try to get a replacement module and 'swap-in you original PROMS?

Here is what we did a few decades ago when I worked at the dealer.

 

To find a specific supercharged ECU would be very difficult but PROM swapping may be an option from my understanding

But you may have an issue with the TPS matching the ECU orientation

 

Maybe so but I have several WDS and IDS computers so.....................
Recalibrating the TPS would not be a problem for me.

I sold all my 6 cylinder Jaguars so I cannot try the ECM PROM swap idea.

I do have some PROMS from the Recall days. I forget which ones.

 

It shouldn't be the MAF, I actually tried swapping MAF's previously and cleaned both of them. It didn't change anything. I will definitely be checking the supercharger because the intake smells really bad, and I've heard lots of complains about stinky supercharger oil.

Oil separator TSB looks interesting although when I tried to find the kit JLM 20709, I found a few people complaining about theirs falling apart. I think it would still be worth it if I can find one.

I nearly have the intake out, what a huge pain. Its all shoved in there like a big puzzle and it comes out as one giant wobbly assembly. And then they ran a wiring loom through the intake runners. I suppose I really ought to add a plug there but I don't think I will.

 

The supercharged version MAF of the engine being a different part # can get mixed up

You should have # LNA1620AA

Genuine Air Box-air Flow Meter-4.0 Litre Supercharged (4.0 Litre Supercharged) For Jaguar Xj 1995 - 1997 (from 720125 To 812255) Classic | Jaguar Land Rover Classic Parts

My opinion is to clean the sensors to get the engine to regulate properly and pursue the oil in the intake later

There are other catch can setups for the air / oil separator

Without disturbing or removing the TPS have you ran it through it's range and don't have a bad spot ?

THE MOUNTING POSITION IS CRITICAL SO YOU DON'T WANT TO REMOVE IT

 

Does your engine get into close loop mode / regulation with the ECT getting above 88 C ?

This is a common thing to this engine and may be a factor in not reaching higher RPMs

 

I have the right MAF, checked it again. I finally got the whole thing apart, it's so unserviceable. I've begun cleaning everything just with dish soap and water.

That sort of paper wrapped tube from back of the throttle body had some small tears in it, and the throttle body is very filthy. The EGR was clogged shut, you can see where a shop poked through it with the inner piece of an old shift cable. I will finish cleaning that out.

None of the throttle body pieces had any gaskets on them, is that correct? Seems like there should be something there.

 

For the normally aspirated there is no gasket between the TB and the intake manifold

genuine Inlet Manifold-4.0 Litre-supercharged (4.0 Litre Supercharged) For Jaguar Xj 1995 - 1997 (from 720125 To 812255) Classic | Jaguar Land Rover Classic Parts

There is one on the IAC valve that is often missing

Just look at it as the bolts tend to shear off , loctited

 

Genuine Throttle Body Assembly-4.0 Litre Supercharged (4.0 Litre Supercharged) For Jaguar Xj 1995 - 1997 (from 720125 To 812255) Classic | Jaguar Land Rover Classic Parts

 

If it's possible that your ECU has gotten wet then it will do all sorts of weird things. That's if you have a bit of rust and the car is rained on. Maybe check the connector in the footwell if so.

 

It appears he may have opened up the ECU but the water damage can uccure as the wires go into the ECU connector on the upper facing side

There is also the issue of the sockets not biting the pins on the ECU effecting the socket crimps to the wires because of missing socket tabs different then corrosion

My wording got mixed up / editing

The Econoseal 36 wire connectors are available with new sockets

 

A bit of an update. I've just mostly been cleaning oil off everything. I do not think the supercharger is leaking anymore. Once I cleaned it off, it hasn't shown any drips or new stains. I checked the oil and found its smells more awful than I had previously imagined. It's definitely not the same smell as the rest of the intake! I will be changing the oil while I have it out, but that's it.

The throttle body seems to be in bad shape. The outermost link with the long slider is working well (I think that is the cruise control?). The inner link the throttle cable goes over doesn't seem to work anymore. It doesn't move the throttle plate at all. It's return spring is also very weak. Plus, both of them are so loose on the axle that the inner link can foul the IAC(?) valve. And that little black arm on the end was just hanging there loose. I'm not really sure what all this was supposed to look like when its working properly.

 

There is an issue with the throttle return not coming back to the Idle stop , yours may be doing the same

This is addressed by a TSB R493 ( Bob gave you the link in his reply ) that targets the normal aspirated version off the top of my head , I do not have the supercharged engine version

Other then the TSB parts replacement some have put a external return spring on the throttle linkage

This could account for the idle not being consistent and returning the TPS back to the idle target of 0.60 volts DC on the middle wire , and this is very precise

Once again do not remove the TPS from the TB just yet but do test it with a meter for resistance if the connector is removed not being powered by a precise 5.0 reference volts DC

There is an adjustment stop screw on the butterfly to not touch as well

The upper long slider link in your pics is the cruise control

Does yours have traction control identified by a tall cylindrical actuator in front of the brake anti - skid module on your right side for your left-hand steering model ?

EGR valve poppet clean ? While you have access to it it may not be the correct one in TSB R493 if ever accomplished

Editing

 

The Supercharged car is covered in the TSB (R493) on page 13 of the document.

 

It has a new EGR valve. I tried cleaning the original one, but after driving about for awhile I found it got stuck again. The valve on the top exhaust side is the only valve for the EGR right? Or is there a second piece to it?

I do have traction control and ABS but I was told they didn't work by the previous owner. He just left it unplugged, which I've continued. Progress has been a bit slow now that Thanksgiving vacation is over. I've been ordering new gaskets and o-rings and such.