I have a Series 3 XJ6 here in Thailand which is UK spec (right hand drive and Emissions B). RHD is correct for here.

When I bought it a little over a year ago, it had been unused for about 5 or 6 years according to the vendor, and was not a runner. I have done a lot of work on the car and got it roadworthy now, after quite a long battle.

I have gone over the fuelling system on my car quite extensively, and the work done includes:

• New fuel tanks
• New fuel pump
• New fuel filter
• 2 out of 3 solenoid valves for fuel changeover replaced
• All new hoses for the fuel system
• All injectors professionally cleaned, including the cold start one and new micro filters fitted
• Injector harness fitted with new connector plugs and all wiring metered out between ECU, AFM, Injectors, CTS etc. (I found two open circuit wires to AFM which had been causing over-rich running problems)
• New coolant temp sensor
• Throttle butterfly set to 2 thou’
• New hoses on Extra Air Valve and the air block with the idle adjustment. New breather vent boot.
• Fuel pressure checked at fuel rail and in spec
• Timing checked
• All vacuum hoses renewed and incorrect connection via ported vacuum from throttle body disconnected and plugged – vacuum connected to rear of manifold plenum. I am convinced there are no vacuum leaks any more.
• Idle set to 900 RPM with A/C on and transmission in P (this drops to about 550 RPM in D)
• Full throttle vacuum switch checked and working ok.

The problem I am having is that the car tends to stall at junctions when the engine is not yet fully warmed up. It will start again pretty much straight away after stalling. Once it is up to temperature (it just goes into the green on the temp gauge, and seldom far into that region), then it behaves fine. The general performance is good, and it pulls well. The tickover is slightly lumpy, but I read that is quite common.

I have removed the Extra Air Valve and tested it. After chilling in the freezer, the orifice opens right up. At ambient temperature it is a little less than half open. When heated up with the hairdryer it closes to just a slit, and with 12V applied to the connector, it closes up completely. So the EAV seems to be working properly. I do have 12V and ground on the pins of the plug to it when the fuel pump is running.

Can anyone think of anything else I could try to prevent it from stalling when cold? I don’t want to increase the tickover setting any more as it is OK when hot, and in fact with A/C off in P it is up to about 1200 RPM anyway which is quite high. Over here, the A/C will be in use all the time as the climate is hot. I have not done much with the idle mixture adjustment on the AFM, other than tweak it a bit to get max idle then use the idle adjustment screw to set the required tickover.

Any suggestions you might have would be gratefully received.

 

a faulty coolant temp sensor and thermo-time sensor comes to mind. Did you replace those?

 

I have replaced the Coolant Temp Sensor

From what I understand about the Thermotime Switch, it only operates for a short period at start-up to activate the cold start injector. As the car starts easily from cold, I haven’t considered this to be a potential problem as I don’t think it does anything after start up

 

ok, so if this only happens when cold, and only temporarily, then the extra air valve might not be doing its job.

 

That was my thinking too. Hence why I removed it and tested it under various conditions. It seems to be performing exactly as it should!

 

since this is a UK-SPEC car., I assume you don't have a extra air switching relay mounted next to the AFM ? or you do?

 

Correct the car does not have that

 

You've covered a lot of bases.

One thing that comes to mind when discussing cold running problems is the double-fueling problem and fix.....

XJ 6 Series III 4.2 - Cold Start EFI Overfuelling

It's not an exact match for your symptom but might be worth a look.

More later. I'm only two sips into my first cuppa coffee and the brain isn't quite alive yet

Cheers
DD

 

Right!

The TT switch doesn't operate unless the key is in the 'start' position and the engine is stone cold

Cheers
DD

 

Thanks for the suggestion about the capacitor, Doug. If the engine is over-rich when cold, perhaps it could cause it to stall at low revs. Today I drove the car to town to buy a capacitor. I was watching the temperature gauge and the car stalled at the first three junctions with temp under 70C, but the next junction, by which time the gauge was at about 75-80C, it did not stall, nor did it thereafter. So the quoted figure of 72C in that bulletin sounds like more than coincidence.

I shall fit the capacitor tomorrow morning and report back if it makes any difference or not.

 

Can someone show a photo of the acceleration enrichment circuit please?

 

I'm not aware of a circuit identified that way.

However, there is a 'full load' circuit to enrich the fuel mixture under heavy load. It is operated by a mechanical switch. Is that what you're thinking of?

Cheers
DD

 

From one unfamiliar with this engine management system:

1. 550 idle is a bit low for a cold engine. Is there a means of upping tht and not having too many idle RPm with the engine warm??

2. My idea of a good warm idle is as much as can be tolerated and not have transmission creep at a stop. Particularly with the AC on!!

Kudos, you have come a fur piece!!!

Carl

 

So I soldered in the capacitor yesterday evening, and have just been for a test drive in the cool of the morning.

Good news! She didn't stall at any of the junctions.

Looks like this is the required fix. Many thanks for putting me onto it.

 

Great to hear your issue is solved.

Andy, kindly do me a favour by showing me a photo of the capacitor you soldered, I need to check and try doing same to my car.

​​​​​​if you have before soldered and after soldered photos please send.

I need to see that capacitor

Thanks

Mike

 

I didn’t take any photos, but this pic was on the Jag-Lover’s forum showing how the capacitor is fitted....although slightly out of focus:

 

Apologies since I did not read all the links but was this “fix” implemented in production in later SIII’s?

I ask cuz my 86 never had this issue

Thanks - Randy

 

No


Some do, some don't.

Cheers
DD

 

Mine doesn't have the capacitor, not sure if someone has tempered with it from how it shows some tapes on it.
Can I get the whole cable unit to buy from SNG?

 

It looks very much like your car has had the capacitor mod in the past, but someone has removed it again. Perhaps they found it and did not know what it was for, so cut it out.

I would recommend fitting a new capacitor there. The taped wires are the two wires across which it is fitted.

New injector wiring harnesses are available from Autosparks but they are VERY expensive.

By the way, are you based in Accra? I was working in Ghana all through 2018 and loved it there. We started in Tamale and later were in Kintampo, Bimbila and Atebubu. Such friendly people everywhere.