Progress

So the new Lambda sensor turned up during the week. Fitted it and was disappointed to find it made absoultely no difference.

So then spent the rest of the day trying other things. First up was checking all the vaccum hoses. I hooked them up to the trackpump and gave them a good high pressure blast, but nonw were blocked. So I did the same thing on the plenum vaccum inlets and they were all clear too.

Then I swapped the throttle body unit with all three sensors from the GTI on to the Rallye and as expected (but I wanted to be sure) that made no difference either. By this point I was running low on ideas, but decided that I would also investigate another issue thet car has been experiencing.

This is the oil pressure light coming on dimly. I first noticed it in spring but it didn’t seem to make any sense as it couldn’t be correlated to any other issues. I decided to investigate any way and found that the wires to both the oil pressure sensor and oil level sensor had become very inflexible undoubtedly due to the fact that they receive several hundred degrees of radiant heat from the exhaust manifold. They are normally protected by an aluminised heatshield, but this had been butchered at some point and there was no barrier to shelter them from the high temperatures.

So I unplugged them both and also disconnected the alternator and pulled this section of the engine loom up to the engine bay to make working on it easier. I cut out the heat damaged sections and fitted in new wiring (from a new spade connector back for the pressure sensor and I had to open up the special connector plug and use some new bullet inserts for the level sender and feed new wire back from these).

With an earthing wire from the connector on oil pressure wire to the body, I started the car up and it ran perfectly. I couldn’t really believe it. So I refitted everything and started fabricating a new heatshield for the wiring. Everything back in place, started the car again and it was back to sound like a Massey Ferguson. At this point I may have cursed a bit.

So back under the car! I disconnected the oil pressure and level sensors and earthed the pressure sensor wire to the body again. Started the engine again and it was still running badly. Disconnected the alternator and it’s fine. Weird!