Since my inital post I've again done a couple of scope tests and also monitored the inlet manifold vacuum.
When I repeated the initial test monitoring the pulse width it made a liar of me by not increasing the pulse width at all during the rough running phase as it did before! Manifold vacuum dropped from about 19" to 15" during the rough phase as well.
As before once it passed through the rough phase of about 20 secs all started to return to normal.
I put it to one side and repeated the test later in the day and this time monitored the coolant temp as well. The temp signal started at about 4.5v and as it warmed seemed to steadily drop and again during the rough running phase didn't seem to do anything weird. All other results the same as before including normal pulse width of about 3.5 to 4msec at idle.
However this time I decided to let the engine fully warm just to see if anything else happened.
When it was fully warm I had a repeat of the injector pulse off scale again! In fact I think the injectors were being turned on continuously, rough running, tending to stall, smoke out the back etc etc. I also noted that during this mayhem the coolant temp signal had also dropped to 0!
I switched the car off, let it sit for a few minutes and it fired up and ran ok or as well as before. Pulse width had returned to normal and coolant temp about 0.8v, what it was before once fully warm.
Not being fully confident in vac gauge use I hooked it up to my own known good Pug 306 and had a play. Vac at idle about 18" rising slightly as it warmed ie about the same as the 307. I then induced faults by disconnecting an injector and then a plug lead. Vac dropped to 15, again about the same as the 307. To me the question is; is the vac dropping because of a mechanical fault or because something else is causing the engine to run poorly which will also make the vac drop?
Interestingly after the previous bad overfuelling issue the MIL came on and the code for No1 coil pack fault was present. This car had the coil pack replaced by the dealer and maybe they didn't clear the code, maybe the overfuelling was so bad causing a misfire its taken as a secondary problem by the ECU?
I'm beginnning to smell a rat with this as it seems amazing that it can have so many faults at once! I thought that the CTS and Injector voltage falling to 0 during the overfuelling saga may indicate an ECU supply/earth problem and hence poor control by it maybe.
Has anyone used one of the "First Look Sensor" tools sold by Senex and also by Pico with their scopes to determine engine mechanical condition?
I should also do an old fashioned compression and maybe cylinder leakage test.
This is getting to be a challenge to say the least!