Sorry folks, this is a long one again!
For the last few weeks I've been having an intermittent problem that seems to happen with no specific determinable pattern whatsoever
It's happened in most gears, at all sorts of RPM, when booting it or tootling along, even sometimes when the car is started (from hot or cold): there is no regular or common driving condition when it appears and it's now getting on my nerves.
What happens:-
Car will sound like a Subaru (as if running on e.g. 4 cyls)
AFR will go very lean (up to mid 20s)
Power will reduce
A bit of spluttering
Sometimes the EML has come on until the fault has cleared or it has flashed on and off until the fault has cleared. It does not stay on when the fault has cleared and it doesn't come on every time the fault is present.
Sometimes the TCL off light will come on and remain on until the car is restarted, irrespective of the fault going away. TCL off does not always come on when the fault is present.
I've had EML briefly on on it's own, EML on with TCL off, TCL off on on it's own: every combination really.
These symptoms can last anything from a second up to, on one occasion, about 60 secs. Obviously when I can see it's running this lean it's a bit scary! The fault generally clears itself within a few seconds but can come and go numerous times through a short journey or not appear at all during a journey.
One day the fault was particularly frequent and problematic. I found a pinhole leak in the fuel supply pipe from my AFPR to the fuel rail so I replaced the pipe. I could see a drop of fuel leaking every 2-3 seconds. Nick Mann advised me to change this pipe a long time ago and I totally forgot about it. For the next 2 days the car ran great and I hoped that was the end of it.
Then the fault got more frequent and more intense.
I then changed the fuel filter (as I've been running the tank low for ages and I doubt the fuel filter had ever been changed). All 6 plugs were replaced with the same type NGK BKR7EIX iridium ones I've had in for the last 2 years. The ones that came out were a bit dirty but had no visible damage and didn't give me any concern about the plugs or anything else that their condition could point me to. These had done 20,000 miles or so and I've wanted to change them for a while and it was a good opportunity to have a look at other stuff that may be causing the problem.
Before changing the plugs I measured the resistance of 2 of the coils (perhaps... it isn't too clear to me how to do this properly and I can't work it out from the workshop manual) as a fault with these was also an option I considered. I measured the resistance from the spark plug connector on the coil to the spark plug lead connector on the coil. I hope this is the right way to measure the secondary resistance. I have no idea about the primary. Anyway I got a reading of 17.3 Kohm doing this on the 2 coils that can easily be removed with the engine cover off.
This seemed a bit high to me but as the 2 were consistent I took a gamble on the third being faulty (and having a different reading) so I bought one from Nutter John. When I got this I measured the resistance and got 9.7 Kohm. This confused me more but I now know, after looking at the workshop manual and assuming I am measuring it correctly, that at least 2 coils would appear to be out of spec (9-13 Kohm secondary resistance). I still don't know about the third coil as when changing the plugs I forgot to check it
When revving the car I could hear a hiss and, sure enough, had a small split in a vacuum pipe off the inlet manifold. Pipe changed and all dump valve, IC and boost pipes checked for tightness. No more hissing!
For the last 7 days the car has run without fault. Yesterday the fault returned when I started it from cold to move it from one work car park to another. My fuel puimp is hard-wired to the battery and I had a problem with one of the wires previously so, in the dark, I attempted to get the back seat out of the way and have a look. I couldn't easily access the area I wanted to so I just gave it a bang with my hand in frustration
Obviously this didn't make a difference to how the car was running: idling with an AFR of 20+
So, in the early hours of this morning, in near total darkness, I lifted the bonnet to have a poke around whilst the fault was present. I had noticed previously that the plug lead to coil pack connection seemed a bit looser that I'd like and that the Magnecor KV85 ignition leads were a bit tight fitting in terms of length so I proceeded to ensure that the lead connections to the coil packs were pushed all the way on. What a nice little shock (literally) I got from one of the leads/coils. I couldn't see any sparking in the darkness but there is electricity 'leaking' somewhere around one of the coils/leads, as my numbed fingers will atest!
I've just had a good look around in the daylight and changed one of the coils for the one I bought off Nutter John (the one I got the shock from).
I also noticed that there is a small hole in the insulator of two of the leads (one being the one I got a shock from). The hole on both leads was orientated downwards towards the block. I have twisted them so that the hole is now upwards... clutching at straws but my thinking is that it would make more sense to have them this way if the spark is grounding to the engine through this hole.
Now I'm at the stage where I think it's definitely spark-related.
QUESTIONS
Can anyone tell me, in idiot terms, how to measure the primary and secondary resistance of the coil packs. I've searched and still can't work it out. I know, from the workshop manuals, that the values should be: primary - 0.5 to 0.7 ohms; secondary - 9 to 13 Kohms.
If I'm measuring them correctly then the secondary resistance of at least 2 of my coils is way out of spec. It doesn't seem likely that the car would run as well as it does (most of the time) if this is the case?
From the photos I've attached do you think I need some new leads or will this not really cause any problem (I think I already know the answer to this one so has anybody got some good condition leads for sale?)
Lead1.jpg
lead2.jpg
The coil pack I put on today (9.7 Kohm according to my measurements) looks slightly different to the original ones on the car and the electrical connector was very tight to get on. Are there different types available or is it just a slight design change?
coil.jpg