Deferred success

The good news is that the engine now appears fully sorted. The two problems that I'd observed - low compression and a faulty MAF can be blamed on a faulty compression tester and a bug in the laptop software. Phew. A lot of time wasted trying to track down non-existent problems due to faulty diagnosis tools, but at least I'm happy with the state of the engine now. Better wasted time than a dead engine, although it means no M3 engine for now...

Pete lent me a different compression tester, which produced numbers in the range 160-175 (cold, dry), which is slightly above what Haynes says I should expect, and all within 10% of each other - so this is completely OK and suggests that there is no compression issue. Assuming, of course, that Pete's tester is not faulty - but given that he's used it before and mine has only been used on the seven, and also that I wouldn't expect it to run at all, let alone with no obvious symptoms, with a PSI of 35 (which is what mine measured), I'll assume mine is broken.

The MAF issue seems to be simply that carsoft wasn't displaying sensible values for airflow on the laptop. We replaced it with a pot, and twiddling the pot made the engine stall, so the ECU is obviously reading it and using the data from it. But still the laptop displays non-changing values as I twiddle the pot, which fairly clearly points to a software bug. Unplugging both MAF and throttle position sensor causes a stall, again, as expected; unplugging just the MAF causes a little twitch in the revs, again, normal. So all signs suggest a laptop software bug.

On Thursday, Will came over and we spent the day going over the car before MOT. Will spotted a potential issue with how the handbrake attached, and very kindly went and made up some pins to attach it with on his lathe (although I secretly suspect he was just missing his lathe after a year apart from it). He also managed to resolve the dragging rear brakes... or so we thought. We also tightened up the suspension bolts, cleaned up some wiring under the bonnet, and probably did some other minor things that I've forgotten.

Today was MOT day. I'd stupidly booked it for 8am so had to get up at silly o'clock to drive there. Insurance sorted (turns out sevens are really cheap to insure, which is cool), we set out, me wrapped up in snowboarding gear. It was wet and cold, so I didn't try giving it much in the way of throttle, so sadly can't report on how nippy the car felt.

Unfortunately, halfway there, the car was getting less and less responsive, and I had to pull over and stop. It turned out that the rear brakes were well on their way to melting - I'm not sure if this was because the handbrake had been on very slightly, or Will didn't get the rear brake adjustments right. I suspect the former, because both were equally affected... wonder if I should have fitted a handbrake switch. After ten minutes, we decided to try carrying on, which probably would have worked, if I hadn't run out of petrol.

I sent Emily off to buy some, and eventually we made it to the MOT centre.

Unfortunately, the short of it is they abandoned the test due to a loose steering rack, and leaking brake fluid. I'm sure the former is just a case of being loosened by the vibrations of being driven for the first time, so an easy fix (tighten the bolts). The latter might well be the fluid having boiled, since I had zero drips in the garage (although of course this was the first time I'd used the brakes significantly), but I will need to investigate this and make sure all the connections are tight.

I trailered the seven home (thanks Simon for the use of the trailer)... repairs start tomorrow; the MOT is now next Saturday. Technically it will be a first time pass as they didn't perform the MOT today, just took one look at the fluid leak and didn't bother, so that's what I will be telling people.

Videos of the first drive to follow...