Hi all.
i have a 1989 he that was running perfectly however it will now only start on full throttle ,runs very poorly (wont rev) with lots of black smoke from exhaust so almost certainly overfuelling or lack of air, if i release the throttle it dies and then will not restart.
any ideas please

 

Hi Mirach

Being a Jag its a very long list but most likely to be the Coolant Temperature Sensor, as if this goes wrong then it can make her run 'Mega Rich'

 

Start by looking for any broken vacuum lines, broken wire, rodent damage, corroded connectors or bad plugs or dirty air cleaner etc

 

When checking vacuum hoses pay particular attention to the hoses to the fuel pressure regulators and the hose/pipe going wayyyy back to the the ECU in the boot/trunk

Cheers
DD

 

That much fuel is usually a failed FPR.

As Doug mentioned with the vac hoses, look inside the 2 small hoses from the FPR to the Inlet manifold spigot. They MUST be dry inside. If they are damp/wet, then the related FPR has failed, and raw fuel is being sucked into the engine.

Then in the boot, the ECU is tucked up inside the RH Buttress, and has a smallish hose coming out of the side of the casing. This hose splits. The ECU operates as follows. NO vacuam = heaps of fuel, Normal vacuam = less fuel, simple when you know it thinks.

OB is also smack on. Unplug the CTS (B bank thermo housing, 2 wires in a plug), take a paper clip, shape it accordingly, and bridge the 2 terminals IN the plug. This will "fool" the ECU to thinking the engine is AT operating temp and lean off the fuel.

The TPS may also be AWOL, age is now against that item.

 

The 'Paper Clip Trick' To Test The Coolant Temperature Sensor but a piece of wire does the same job

This was on my XJS 4.0L but works exactly the same for a V12

 

Thanks guys!! Temp sender plug rusty, gave it a good clean and wd ,fired up as sweet as😀😀

 

I had a really bad rich problem. It was a bad/dirty ground, in the bundle bolted to the inner fender near the battery (LHD).
Rob