Today I had a couple of hours free, so I set about replacing the crank sensor plug.
I initially wanted to replace a chunk of harness, and actually bought some nice flexible silicone wire to do this.
However I tested the original wires, and found them to be absolutely fine, so I made an executive decision and simply replaced the old plug, with a shiny new one.
When ordering the plug, I decided to spend a few £ more and bought gold plated connectors, instead of the factory tinned connectors.
The first job was to get the plug to where I could actually work on it, without being stuck head first in the wheel arch.
This particular branch of the harness also has the turbo actuator plug on it, but luckily nothing else.
So I disconnected the crank sensor plug and turbo actuator plug. After this I needed to remove the air intake pipe, between the air filter and turbo intake pipe.
Once out the way, the engine cover came off, which allowed me access to feed the now free harness branch up to the top in to view, once all the clips holding it in place were removed.
After I could see the plug in question clearly, I tested the integrity of the 3 conductors right back to the ECM multi-plug, all were showing just a couple of ohms resistance. At this point I decided to simply change the plug.
The first job was to disassemble the old plug, as I wanted to know how to put the new plug back together correctly.
I was 99.9% sure, but just wanted to be 100% sure, as I'm OCD!
So I started taking the plug into its component parts, seeing exactly how it had been assembled in the factory. Obviously I needed to keep the 3 connectors in the same positions in the new plug, so those were noted.
Once apart with the connectors exposed, I cut them off, as they were being replaced.
I then took the seal off wires, and finally the plug body, the lid of which has the 3 holes for the wires to emerge.
I then stripped 5mm of insulation from the 3 wires in readiness for soldering. I'd already decided to fold crimps with pliers and solder them too, as I didn't have the tiny crimper tool needed for them. Besides I prefer solder joints, as I believe they're less likely to become bad connections in the future, especially if they're likely to get wet.
Before I fitted the new connectors, I slid the new plug body lid over the 3 wires, making sure the order was correct, followed be seal, which held the plug body lid on the wires, which were now ready for tinning.
Soldering also gave me the opportunity to try out my new Pinecil USB C powered soldering iron from Pine64.com, which I bought about 12 months ago, and hadn't used, other than a quick test when it arrived.
I used proper juicy lead solder, as I can't be doing with the lead free stuff, particularly in on important joint like these.
Needless to say, the soldering iron did what it's supposed to do, and the joints are nice and secure.
At this stage it was just a case of putting the new plug together, so it mimicked the old one.
I then checked the fit in the new crank sensor
before I fed the harness back down it's correct route, so the 2 plugs ended up where they needed to be.
At this stage I removed the old crank sensor from the engine, and fitted the new OE Febi Bilstein replacement I'd bought.
The new plug and sensor socket were given a liberal coating of silicone grease, which will keep any water out, and help the seals seat correctly.
The turbo plug was similarly treated, to prevent water ingress, and the harness was zip tied back on to the clip, helping prevent movement of the harness.
I also noticed that there was evidence of a tiny coolant leak, with a couple of red drips on the lower half of the engine. The coolant has dropped about ¼ of a litre since November, so I'll not be doing anything about that just yet. I also noticed some oil dripping off the lower boost pipe between the intercooler to the throttle body, so it appears there a leak there somewhere too. Unfortunately the bumper needs to be removed to get to the intercooler end of the pipe, so that's a job for another day.
To finish off, I put the top of the engine back together, then went inside, inserted the key and pressed the start button. The engine cracked over it's usual 1 second of cranking, then fired up as normal.
On the test drive it seemed no different to how it had been since I replaced the sensor at the road side last month. After I'd fitted that sensor, the occasional dropout when hot hadn't reoccured, however there was still an obvious misfire under 75% throttle or more when cold.
At least I know that the sensor and plug are new, so the random hot dropout should be a thing of the past, as I believe this was caused by the plug to sensor connection breaking down when hot.
I'm not sure of the cause of the cold misfire, but as it only does it first thing in the morning, and I feel it's likely just 1 cylinder, but I can't see if that's cured until Monday.
I guess it's possible that the weeping boost pipe is the cause of the cold misfire, although I'd have thought it would do it all the time, not just when cold.
Investigation will continue on that particular issue.