I've repaired the interior heater pump motor that's in in the engine bay behind the engine and now the engine won't run properly.
To make some space to do the job I took the throttle body off and undid about half a dozen electrical plugs, all of which I've since cleaned with electronic cleaner spray and dried with a hair drier, but things are still the same. The engine revs right up by itself on start up then settles down to an erratic tickover before either stalling or revving up again, it's undriveable.
There are multiple error codes:
Air flow (MAF)
Air temp (IAT)
Pedal position sensors A and B
knock sensor
Multiple cylinder misfire detected.
There's no way all the parts have failed at once. I've cleaned all the connections multiple times and I'm confident they're clean, dry and together properly. And I've checked all the fuses. Maybe I should try and cancel the codes, but as I don't really know much about the electrics I'm worried that if I did that I'd mash up things further.
Now I'm stumped and I'd really appreciate some input.
Thanks in advance.

 

Clear the codes and then see which ones pop back up. Post the result and we can then take it from there.

 

Agreed!

Clearing the codes won't 'mash' things up further, so let us know.

It's usually only one thing wrong that sends a multitude of error codes out like this (the voice of experience talking here).

I know this might sound stupid, but make absolutely sure that the rubber gasket on the bottom of the flexible black plastic air flow tube that connects to your throttle body (coming from your MAF sensor) didn't accidentally fall off.

Also I recommend removing that same air flow tube and check closely for any cracks or burn-throughs (happened to me) that might have manifested itself during the original removal.

Having an absolute air-tight seal from the MAF sensor to the throttle body is imperative.

The guy I bought my cat from sold it to me for $6,000 less than book price simply because he couldn't get the check engine light to stay off. His local Jag dealership couldn't figure it out either. A bit of black silicone sealer on the bottom of where the 'flex' occurs, and problem solved. It had a small burn-through.

Keep us posted.

 

Thanks chaps.
I cleared the codes and fired her up again.
The first time whilst still running erratically it went to 'restricted performance' and gave misfire codes for all eight cylinders and 1316 which is the injector circuit apparently.
I cleared the codes yet again and it gave me error code1642 which is 'fuel pump monitor circuit'.
Bowmanconsult. I might be being daft but I thought the MAF valve was at the exit of the airbox, if I'm right there isn't a small pipe from this to the throttle body, just the main large diameter air feed pipe running from the airbox to the throttle body. There is a corrugated small diameter plastic pipe running from the back of the throttle body which splits into two before the other two ends clip onto either side of the intake manifold. The seals on the three ends of this pipe are still there, I've just checked, but the pipe is very old and hard so I think I'll take it back off tomorrow in the daylight and check it for cracks.
Thanks again.

 

1642 is actually a CAN bus fault, probably caused by the code reader. (Generic code lookup tables are not always correct for Jaguar).

As a guess, are you sure that you re-connected the vacuum hose to the fuel pressure regulator?

I would suggest you check you measure the fuel pressure at the schrader valve on the fuel rail, given your symptoms.

 

Thanks White XKR
That's interesting about the codes.
I hadn't actually removed the fuel pressure regulator vacuum hose as I'd only removed the main throttle body, the top part, and the hose looks okay. I didn't realise there was a schrader valve, but I've located that now. If I don't find any air leaks in the morning I'll try to find a gauge for the fuel pressure, I suppose it's specialist piece of kit but I'll ask at the local car parts shop. I don't suppose you would know what pressure I'd be looking for would you?
Thanks again, it's great that you'll both spend time helping me, I really do appreciate it.

 

It should be about 42 PSI idling. This schrader valve is the Ford style, which is slightly smaller than most schrader valves, so make sure you have the right adapter.

 

You're a mine of information.
I don't know if the quality is much good but I've just spotted Bergen ones on Ebay for about £30 (UK).
Thanks a lot.

 

The first thing to do is to try to retrace your steps in the removal process. It sounds to me like you've plugged something in the wrong hole. Look at every single thing you took apart.

 

The large diameter air feed pipe is exactly what I was referring to.

If it's brittle but still intact, it might have developed a crack at any of the corrugated areas when it was removed and may be allowing too much air to pass through.

Worth a look.

 

Thanks both.
I'll take the throttle body off again tomorrow and check everything meticulously.

 

Silly boy!
As soon as I removed the throttle body I saw that the breather pipe from from the left hand rocker cover hadn't been refitted to the manifold so it had been sucking in air, I don't know why I even took it off. Then when I started the engine it ran perfectly. Before I asked the question yesterday I was thinking the problem was electrical, it was your answers that pushed me in the right direction.
But my relief was short lived as I've found that on the one side of the subframe the top wishbone mount holes are elongated, so now I'm thinking I probably need a new subframe, unless it can be reamed and bushed, any ideas there?
Anyway, thanks for your help everyone.

 

How badly elongated is it, worse than this?




I have seen that others have had a sleeve put in.

 

It probably is worse than that, the hub slops slops backwards and forwards quite a bit.