So it started with a few symptoms: First was a slight hesitancy at 2400rpm, barely noticeable, but enough to warrant some investigation. Secondly the popping noise on the bank 1 exhaust, which has been attributed in several posts to various things ranging from bad exhaust valves to leaky secondary injectors (as above) to ‘they all do that sir’.
The V8 works on the wasted spark principal, so I did a continuity check from the corresponding HT leads: (thanks CaptainBigleux)
Cyl 1-4 was 36MOHms, and increasing (similar to charging a capacitor…not good)
Cyl 2-3 was 33KOhms…OK
Cyl 5-8 and 6-7 were not able to be tested as the electrode detached when I took the HT leads off. Obviously…not good.
Suspect some water had got in there at some point…as CaptainBigleux mentioned.
So, at this stage I ordered a new set of HT leads from JAE, sulked a bit, and started to look into how to remove the plenum chamber. Then I called my local mechanic, then I sulked a bit more then whipped the trunk out decided to have a go at it myself.
Fortunately, there was a fairly well illustrated post on LEW (http://www.lotustalk.com/forums/f164/plenum-removal-injector-upgrade-178353/) that helped back-up the brief description of the plenum removal procedure in the service manual. I wouldn’t say it was easy, but it came off eventually with the help of a Jedi mind trick to detach the Idle Air Control connector. I tried mirrors, headlights, flashlights but nothing worked. Your hands always get in the way, and you have to think backwards….better just to do it blind. I eventually removed it using 8” long nose curved pliers. It was a case of feeling the connector and then locating the pliers on the wire loops. Fun.
I replaced the HT leads one at a time and labelled them with those clip-on numbers. When I got to #8 the coil connection felt more loose than the others. Closer inspection revealed a rusty terminal that obviously was not going to heal itself. Back on the phone to JAE for new coil packs. Decided to change both as I did not want to go through this joy again.
The new coils measured about 11KOhm on the secondary side (15KOhm via the HT leads), and 0.8Ohms on the primaries. Satisfied with the electrical side of things I set about installing the new coil packs, only to discover that the 6mm hole patterns didn’t line up. I opened the holes up to 8mm and they went in OK. The coils sit inside the ‘V’ and there is very little room for all the wires. It took a bit of trial and error to get them neat and tidy. I would recommend replacing the M8 bolts with allen screws to make installation easier. I managed the re-installation with a short section of ¼” stock to drive an M8 socket. During this process I noticed that the spiral wrap that protects the HT leads had disintegrated. I verified the melting point by testing it in the oven. The existing stuff meted at around 250°F. Tried the cheap crap from the local auto parts store (“oh this can withstand any temperature…”), melted it at 200°F in the oven, then sourced some Teflon (450°F) spiral wrap from Brown Aircraft Supply. I ordered 8ft, which is plenty for the HT leads and enough left over to do the O2 sensors (different topic).
“Re-assembly is the reverse of the above…” or so they say. I had good notes on everything, but after spending two weekends trying to get the plenum back on I gave up and had it trailered it to my local mechanic, which I what I probably should have done in the first place.
So, back on the road. Ran it through the OBD drive cycle today and it is running as sweet as a nut. The hesitancy (suspect this was coil connection #8) and the popping (unburnt fuel in the cat) have gone away. This has definitely been a learning process and hopefully there’s some info here that others may find useful. As always, YMMV and as with everything Lotus your best friends are patience, a magnetic retrieval tool and ibuprofen.