Update time !!! I haven't forgotten to update the post - I just haven't been able to do anything about the problem. Time, money, blah blah blah.
Recap. Since December I have needed 3 attempts to start the LC followed by 5-10 minutes of being limited to 10mph - before a restart makes things good to go (with a pretty little orange comfort indicator on the dash of course). After those 10 minutes, all is good. Runs as well as an 03 with 130k on the clock can. Starts like it should on the button for the rest of the day - even if left for 8-10 hours. Seems it needs a solid 12 hours sitting to be a problem.
As per some of the posts here (thanks for the part number
@karl2000 ), the Air Temp Sensor is indeed listed in the workshop manual as one of the suspects for the reported fault code. However, they are £140 quid. Hence the wait.
A couple of days ago I decided I had no choice, bit the bullet and ordered one. I then felt the panic and decided I had nothing to lose by seeing if I could work out if it's actually broken. Here was my thinking...
- I've got a new one on order - what can go wrong?!
- I don't know how it works - but it can only be physics.
- Remove engine cover. Unclip wire connector.
- Use voltmeter to check angry pixies are making it to the clip - assume that the measured "just under 5 volts" is ok
- Remove Air Temp Sensor. Look at it. Smell it. Poke it. Zoom in on it with phone zoom magic. Ponder.
- Note how much oil/diesel residue it has on it.
- Consider that it must be some kind of resistor with air temperature changing the flow of magic pixies through it.
- Remember the magic pixies in electricals like Isopropyl alcohol.
- Pour the pixes an Isopropyl drink. Dunk the sensor in said drink. Wiggle and woggle it.
- Reinstall sensor.
- Wait patiently for the morning to come to see what happens on a cold start.
.....
.....
- Just about starts on the first try.
- 5 minutes of being limited to 10mph.
- F#@!!
- This morning it also started first time - but with a similar (though shorter) 10mph restriction.
So that's where I'm at. Picking up the new sensor tomorrow.
I did think about measuring the resistance across the sensor connections while I make the sensor hot and cold (hair dryer and ice bucket maybe). Physics suggests the reading should change if it's working - but without having a clue what reading I would be looking for across what temperature ranges (that I couldn't accurately measure) I'm wasting my time.
Decided I'm just going to risk the money. It only takes 5 minutes to fit. A garage would probably charge me that in diagnosis fees alone just to discover it's not the sensor - that I still would have had to pay for anyway.
So.... will update later in the week once fitted.