Smooth start up Rough Idle 1988 XJ-s HE V12 CEI ignition (Australian Delivery)

Thanks Greg, What sort of money are they going for in the US? I might try RockAuto they always seen pretty reasonable, and they deliver to Australia; although if I could shop by a Chevrolet model it might make it cheaper than having Jaguar in front of the search: any model you can suggest?
Thanks, Chris

Christopher - RockAuto has the ACDELCO D1906 for USD 41.79 - they do show the specs for it and the GM OEM part numbers - Tex.

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It’s a very good thing to change your Ignition Amplifier, but it only controls spark.
Your blowing smoke/too rich is a separate issue.
Check the Base Fuel Map (details in the Book) and if your 0² sensors work.
Is the vacuum line at the ECU intact?
Did you ever check your Coolant and Air Temp Sensors?

Good evening Aristides, yes spark is currently an issue as the car idle is very rough i.e. the exhaust pattern would suggest I have a quite bad or irregular spark; I am firing intermittently on both banks (LHS is worse than RHS). So spark could be an issue as well as the other symptoms observed, which are:
a. Too rich: smoke appears at throttle rev, above 2500 - 3000 rpm;
b. No power on acceleration: timing set to 18 degrees BTDC at 3000 rpm vacuum advance isolated.

Checks made:
a. Vacuum hiss noted at ECU feed hose in boot;
b. CTS is new: stops car when disconnected, runs/idles just as bad when terminals shorted together;
c. ATS did actually make a small difference when disconnected - slightly higher revs; no difference when shorted.
d. Inlet manifold vacuum as above.
Thanks for all your advice.

Thanks Tex, on inspection of my Amplifier, I’m oredering a new one. The wires are all very brittle (in fact the zenner diode one broke off the resistor block when I was checking the amp module for serviceability). I have reconnected it with a very ordinary soldering job but it is very much on its last legs. Cheers Chris

Thanks Richard, the main reason for making sure the TPS was serviceable is that according to Grant Francis the TPS, and the throttle butterfly settings are fundamental to establishing a basis for the idle, and advance settings in the tuning continuum. I’m following the bouncing ball at the moment, and trying to be as methodical as I can. Cheers Chris

I don’t believe you should be able to hear a hiss from the ECU in the boot/trunk. There is a sensor in the ECU that measures the vacuum. It has a diaphragm in it, I think that diaphragm might be ruptured. I’ve been told that this vacuum measuring part fails often.

If you’re always getting the idle reading, you won’t be getting more fuel when you accelerate. I have a test rig for a 3.6 ECU & happy to test it for you. You could just try sucking on the vac pipe into the ECU.

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G’day Jim, I meant when I disconnected the rubber pipe from the ECU I could hear a hiss and feel a suction. So this component of the contiuum is working.

My car is a V12 but I imagine there are very few differences between ECUs knowing Jaguar’s prediliction for standardisation. So where do you live? I’m in Newcastle Australia.

Thanks Dieselman, I must admit I have been reluctant to conduct this test as I am very hesitant to stick anything into the cylinder and turn the engine: you mentioned a ‘follower’ is that a special tool or just a stick? However, as a mitigation, when we had the car apart in Darwin we did reset the cams when we replaced the cam chain and tensioner using a Jaguar cam setter: because an idiot in the workshop rotated the engine with the distributor out.
Intake vacuum is 15 Hg/" as measured at the RHS inlet manifold

I’m hoping its a simple case of a bad ecu. These Lucas ignition V12s are not that complicated. It may take a lot of work to get them to run perfectly smooth, but they should easily run.

G’day Grant, sorry to disturb you, but I’m not having much succes on getting my '88 XJ-S HE to run smoothly, and I seek any advice you maybe able to offer. I’m assuming you can see the rest of this thread and that I have followed your tips and advice re setting up the engine for tuning, as well as the very welcome advice offered from other members.
A bit of history, the car had a leaking rear main bearing seal, and I had the lads in Darwin (Darwin Radiator repairs and auto) have a go at replacing it. One of their less skilled techs rotated the engine whilst the crankshaft and cams weren’t connected to each other (having dropped the crank down to access the seal - yep)! Recognising that this was probably very bad, I got them to get the cams and crank realigned using the Jag cam shaft jig, replaced the waterpump, camshaft chain (rooted), and tensioner. Cams were in good nick.
After much effort trying to get the car to run smoothly, I was posted to Newcastle, car still very unreliable - started well, and ran but was susceptible to stalling at idle. At this stage I took the car off the road to overhaul the rear cage, and when completed restarted into the tuning issue again. Initially the car started and ran ok, with a slight miss at highway speeds, gradually getting a worse stumble until it ran very roughly, and stalled at idle: roughly half an hour from cold. So I put the car on a dyno here in Raymond Terrace: Car running lean, power at 150 HP.
Had all the injectors off, cleaned and flow tested at the dyno place, new filters, new pintles, replaced all underbonnet fuel line, ferrules, and fuel clamps.
I addressed the lean problem by checking fuel pressure (39psi, new fuel filter, sump tank clean (it was clean), blow through fuel lines (clear), Fuel regulator RHS = OK, LHS rooted, I thought beauty solved it! sadly no difference, other than now I appear to be running too rich.
So now I picked up on your various posts on how to make your XJ-S reliable - jump in it and drive to Adelaide reliable etc. Accordingly, I have done the following:
a. Throttle discs/bodies cleaned;
b. Throttle discs set to 0.002" gap. Made sure rods weren’t impeding closure;
c. TPS set to 0.32 - 0.36v mine is at 0.325v (my original TPS was rooted now replaced);
d. Plugs initially set and gapped correctly (probably a bit sooty now);
e. New fuel regulator (LHS) replaced (original one rooted);
f. Timing initially set to circa 10 BTDC at idle;
g. Followed your “HE Tune up Grant’s Way” which sadly didn’t improve things:
(i) idle can be improved by rotation of dissy although still rough/missing badly;
(ii) performance can be improved by rotating dissy but still stalls at idle.
h. I checked that when rotor at 1A the harmonic balancer timing mark was at 10 BTDC;
i. CTS renewed although it was good;
j. ATS checked ok, although as you noted it doesn’t do a great deal;
k. re checked the AAV, working, I had earlier got a new bulb assy from Jonas in Latvia/Finland…;
l. Set the timing at 3000rpm at 18 BTDC (against your direction but just to see how far I was out - not much);
m. Vacuum advance works;
n. Inlet vacuum is 15 Hg/" measured on RHS inlet manifold;
o. I have now removed the cold idle setup on the RHS leaving the dump valve, connected to the Vacuum advance as per Caspar Graham (You tube - Aussie Daimler V12) in the vain hope that a component of that system was rooted and affecting performance.sadly no improvement;
p. I checked the amplifier unit, mine isn’t in very good condition, although working? Wires inside are brittle, Zenner checked (it is acting like a diode but that’s as far as I can check). Cap measures ok at 1uF. Tacho works…I have ordered a new amplifier unit from SNG at vast expense;
q. Adjusted the ECU knob left and right which didn’t seem to do much, so I returned it to the mid-point. ECU Vacuum feed is good, hiss when disconnected, and definte vacuum detected.

So that’s where I am at. Any advice gratefully recieved, because I’m running out of good ideas.
Cheers Chris

Most people use a long screwdriver, but a wooden/plastic stick would ensure no risk.

The idea is the follower simply rests on the piston crown and rides up as the piston rises.

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