CitroJim wrote:Took my V6 to karate this morning. It's definitely running very beautifully and better than it was before the new belt and all the recent TLC
Is it the new plugs, all the cleaning of the inlet tract or the fact the engine ECU has been reset for the very first time in my long ownership of the car? It was the first time for me the battery had ever been disconnected...
It isn't valve timing as with the old belt the timing was observed to be spot-on..
Simon, I'd be interested in your views as the difference is tangible
Interesting Jim - you'd have to describe the nature of the difference in performance in a bit more detail to make a guess, but it could be a combination of all three.
As you say it's probably not the valve timing, assuming all the cams were able to pin perfectly - on my old V6 the timing was basically right, but two cams were about 1/4 of a peg out so wouldn't quite pin down until being tweaked - after we fixed that there was little if any improvement.
Cleaning the intake tract around the butterfly can make it a little bit more snappy and responsive when you take off from stationary with a very light throttle as a gummed up butterfly introduces some dead band in the bottom end of the throttle range.
How were the old spark plugs, and did you change them to a different type ? I've come to the conclusion recently that the ignition system on the ES9J4 is a wee bit marginal for the job at hand in terms of spark voltage/strength - it's a very high compression ratio engine (which means high peak cylinder pressures and high required spark voltage) plus its waste spark which increases voltage demands further as the spark has two gaps to jump in series. When everything is in tip top shape I'm sure its fine but throw worn plugs, leads or coils into the mix and an intermittent misfire can easily develop especially at full throttle...
The spark plug leads don't seem as tough and reliable as you'd hope - I had quite a bit of trouble with the plug leads on the old V6 (the originals had intermittent breaks in two of the wires that could be measured with a multimeter and one replacement set were faulty in some way too) and I'm pretty sure that the leads on the new V6 are faulty too. A couple of times now the performance of new V6 has gone down hill quite a bit especially at full throttle and I need only wiggle the broken spark plug lead guide around on top of the manifold and the performance is instantly back to normal - so I'm guessing it too has intermittent breaks in one or more wires.
Is it possible one of your spark plug leads is the same and has an intermittent internal break when flexed in a certain way which has just found itself sitting in a more favourable position after the manifold has been out and gone back in ?
The battery off ECU reset definitely can make a difference - but only in cases where the ECU has learnt bad data due to a pre-existing condition. For example when I first got new V6 the performance was really flat and poor all the way that I drove it home, until I did an ECU reset when it came back to normal for a few weeks.
I'm not sure how it had got itself into that state - one theory is that a combination of very hot (28+ degrees) sunny weather and the long trip back from Plymouth on 95 octane fuel was enough to force the ECU to knock the timing back quite a bit, since knocking can be worse with very hot temperatures...
If I had to guess I would say the change that you see is mostly ignition related, as I'm certainly seeing a big change in performance with my new one just by moving the plug leads around a small amount...if the improvement in performance on yours disappears again I'd suggest changing the spark plug leads next time the manifold is off if you've never replaced them before...
Shame the vendor does not seem to say if it has a leather interior. I guess as it's a V6 it will.
