Hi everyone again – good to see the engaging discussion and Bleasie – good to see you back on the circuit and that your hard work with the original Cabriolet register lives on.
(PS. all of my comments refer to the 3.6 6 cyl AJ6 engine)
At the end of the day, there are several components in the fuel injection system and unless you are well versed in fault diagnostics (which I guess most of us are not) and if you don’t have an “expert” at hand to pin the problem down to a specific component, then fixing these problems tend to be a process of tiresome elimination – so its best to pick the cheapest/easiest things first as its easy to spend a lot of money replacing perfectly good components (I’ve got a few in the garage!).
Back to AJ6 engineering which Stig and Alex mentions, this is a top outfit run by Roger Bywater – what he doesn’t know about the Jaguar fuel injection systems isn’t worth knowing. I think the mod that Stig has had done is referring to an idle richness problem on the 3.6 engine and AJ6 Engineering fit a small potentiometer in the ECU as part of this mod – this pot can be adjusted to give the best idle running (instructions are supplied with the mod). I don’t think that this problem would contribute too much to the flat spot which we are discussing – I had this done when trying to sort my engine out but it was the throttle pot replacement which eventually fixed it.
However, it may be a good idea to send the ECU to AJ6 for checking (not particularly cheap but good for peace of mind).
I sent Roger my engine ECU after the engine conked out (and after checking everything else in the ignition system) and he found a load of dry joints inside – upon refitting the repaired ECU, it was like having a new engine – fabulously smooth and improved power and fuel consumption compared to before.
Laurence – back to your comments – I bought a replacement throttle pot from SNG Barrett, but the other Jag parts specialist probably also stock these.
Also worth checking is the vacuum pipe which runs from the engine to the ECU in the boot – simply remove the pipe from the side of the ECU and if the idle changes dramatically, then the pipe is OK.
Don’t forget the injectors – these are all old engines now and any engine will benefit from an injector clean/check – there are a few places who do these – I’ve used “Injectortune” for this – remove them, send them off and you get the same ones back completely overhauled.
You may have gathered by now that I’ve been completely through the injection and ignition system on my engine in the quest to get it running like a new engine – I think that I’m more or less there now.
Don’t forget that these engines need to be used and don’t be afraid to use the power (when you legally can) – a good “clean out” works wonders!
Hope that these ramblings help……..