Hi

I have a 1986 XJSC HE that stalls at idle.
Doesnt matter if engine temp is cold or hot. It wil run at 1000+RPM if I hold the accelerator, but once I take the foot off it just gradually dies and stalls. It does this in Park. Haven't tried in gear.
I have replaced the Primary and Secondary Ignition Coils with a new Bosch type. I have replaced the Lucas AB14 Ignition Amplifier with a brand new identical unit. I have mounted the amp forward of the radiator in the old secondary coil location. I have also rectified a few bad ignition terminals, including the injector signal wire.
It feels like it needs more fuel...
Car has 210K. Its a 5.3 Unleaded, non-air pump model. Distributor Cap, Plugs and Leads have all been replaced at 180K.
Car had been sitting for past 6 months. Prior to that it stalled at speed, but was fine at idle.

I have read a few previous posts, but some fresh opinions would be appreciated.

Cheers.

 

FYI, new coil is:
Great British Cars: Jaguar V12 uprated coil DAC6093, Jaguar

New module is:
Great British Cars: Electronic Ignition Module / Amplifier For Jaguar DAB112, Electrical

 

First up, YOU ARE NEW, so welcome to the real world of motoring, fun will be had, and eventually the Jag will be sorted hahaha. ENJOY.

My first suggestion would be to ensure the throttle discs are set to the correct 0.002" disc gap. Then reset the throttle cross rods correctly.

Whilst you are at the throttle discs, get some clean rags and some "carby cleaner" solvent and give the throttle housings and discs a GOOD clean, as they do build up "black goo" that reeks havoc with idle cold or hot, mmm.

I am going to assume you gapped the spark plugs to 0.025"?????.

The fact it stalls cold or hot is sort of eliminating the AAV for now, but it may re-appear.

Many other items may be related to the issue, but I like to start with the basic simple stuff first, it usually fixes things without grief and mega $$.

 

Welcome to JaguarForums NPH.

I concur with everything Grant mentioned however I would also check the AAV (Auxiliary Air Valve) if after you have check/cleaned all that he recommended and still have a stalling problem.

Simple check of this would be to disconnect the hose between the valve and the intake manifold (sometimes this is easier said than done because this hose is fairly ridged). You will need to partially block the opening on the manifold with something (hand, rag, piece of wood, etc.) There is a lot of suction here so make sure nothing gets pulled into the engine when you start it.

The idea here is to see if the engine still stalls when this hole is opened up. You want to be able to move whatever you have blocking this hole so you can let in more of less air. Try starting the engine with the hole totally unplugged (be ready for the engine to run at a much higher RPM).

Play around with the opening to see if you can hold a good RPM.

Before starting this test... you may want to check to see if any air is being pulled into the AAV, by checking the inlet inside of the air filter. (follow the inlet hose to the air cleaner). Should be a good amount of air going into the AAV when cold, and less after the engine warms up.

Reply back to let us know your findings.

 

fuel pump or IAC.

 

Thanks for the suggestions guys, will keep you posted. (Don't hold your breath though!)

 

Ok, I fixed it.

Culprit was a a brittle and frayed wire coming out of the Ignition Module and going to the Injector Sensor wire.
From memory, this Injector sensor wire is shrouded by an earthed interference braided outer wire. It also terminates to another wire that goes back up the loom somewhere. At times the sensor wire would short to earth, losing signial to the ECU for the injectors.

Whilst at it, I purchased a new Ignition Module, and mounted it forward of the radiator. Where the secondary coil was.
Both Primary and Secondary coils were replaced with a single unit.
If you want to do the same, be sure to isolate the signal wires coming out of the distributor. These also need to be screened to earth.

Fuel pressure tested fine.
No air leaks past throttle bodies. Vacuum test good.
New 670CCA battery also helped too.
I'd love to replace all wiring looms in the engine bay. The heat is a killer.


Regards
Nick