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Getting Nowhere Fast.

After getting her painted, and changing the registration over, you would have thought that Vikki was finished. Oh no. Not in the slightest... 

She hasn't been out a lot this year, mainly down to the weather. But one of the big excursions saw her at this years Shuttleworth car show, where I met up with Peter & Robin who came over in their sportsters as well. During the course of the day, we all noticed that from certain angles, the paint work on both the driver's sides wings was 'crazed' - but it appeared to be under the paint. It's one of those things you need to see to understand, and unfortunately the light has to be right, and even then it doesn't show up on photos. So I can't give you an example. 

Anyway, as it looked as if it was a flaw in the paint, I took it back to Normandale for them to have a look at it, as they said they'd rectify anything if it wasn't to my liking. They took one look at it and knew exactly what the problem was - the gel coat under the paint had cracked, as it was to brittle. When the wing flexed whilst Vikki was out on the road, the fibreglass bent, and so did the paint - but the gel coat didn't.

Anyway, this meant that all the paint had to come off, the gel coat had be ground back and then it all had to be redone - this time with some flexible filler. And as it wasn't the paint at fault, I'd have to stump up some more cash. But the Normandale guys took pity and said they'd do me a deal. So I left the wings with them, and laid Vikki up in the garage.

Whilst she was off the road, I thought I'd try and get to the bottom of the annoying idle issue I've been having ever since she was put on the road. M20 engines are supposed to idle at 1000rpm at cold, and 800rpm when warmed up. Vikki has only ever idled at 1000rpm - and I've never found out why. 

Anyway, long story short I narrowed down a long list of culprits to the Idle control valve circuitry in the ECU. It would appear that it's always been a weak spot in the initial version of the Motronic ECU that the donor car had. So I bought a replacement ECU of E30Zone, fitted it, and the bloody thing did exactly the same thing. No change at all.

I then read about the transistors that regulate the idle valve where normally the issue when this sort of thing occurs - so I ordered some replacements with the aim of replacing them in both ECUs. But when I opened up the case to do the swap, I found this horror show:

And when I opened up the other, it had exactly the same problem! Either I was unlucky with having two ECUs blown in exactly the same place, or plugging the spare one into Vikki's engine loom had toasted it. I settled on the loom, and decided to replace the lot, for a more up to date Motronic system.

I bought a full Motronic 1.3 system from a seller on E30Zone (ECU, trigger wheel & sensor, inductive pick up for cylinder 6, engine loom, fuel rail with 6 injectors & all the wiring) for £100, and got a spare Idle Control Valve from Robin.

Fitting it was a pig. Fitting the original loom was easy, as there wasn't any bodywork or engine ancillaries in the way. This time there was - so there was a lot of blue language when it came to put it on the car, and a lot of blue language from Pauline as I stripped and re-wrapped the engine loom on the dining room table.

Anyway - New ECU dangling from the much bigger (more on that in a minute) 55 pin plug:

New Idle Control Valve, Air intake boot (the new valve is a different shape, so needs a different boot) and large circular diagnostic port in place of the old, smaller D-shaped one:

New crank position sensor (silver can with orange ring at the cable end) and toothed trigger wheel - this replaces the old main pully and the two sensors that used to be in the gearbox bell housing.

The cylinder ID sensor - it's inductive, and picks up when cylinder 6 has fired.

So, its all in and it all works - which is nice.

What isn't nice is the fact that the idle is still too high - from cold it's 1200, but it does drop to 1000rpm when warm. So it means that the ECU is doing its job, and regulating the idle valve correctly. It does mean that I must have a vacuum leak somewhere down stream of the airflow meter. Joy. 

So I have ordered a whole replacement set of seals and gaskets for the intake side of the engine, and I'll replace any that need to be once I've done a smoke test to see where the leaks are.

A smoke test? Yes, a smoke test. It involves blowing coloured smoke into the engine, under slight pressure, and then seeing where the smoke escapes. I've found details on making a home made smoke machine using an empty tin and an old diesel glow plug, and I'll post details up of it once I've done the deed.

Other things I've done (or started) whilst awaiting the return of the wings - I've knocked together a small 1 watt amplifier to pre-amplify the output from the bluetooth module. I'd found that whilst the system works great at low speed, once you get on a dual carriage way or motorway, you could only just hear the music or the person on the other end of the phone using the max boost the intercom had built in. This overcomes that by upping the signal before it gets to the intercom.

Rather than re-invent the wheel, the amp is a £5 kit from Maplin in a plastic project box - but I've put the dual gang linear potentiometer that controls the gain / volume on a fly lead (hurrah for cat 5 cable!) so I could put it somewhere close to hand.

That being the windscreen stay behind the dash - it's easily accessible due to the shape of the dash there, but still out of sight.

Whilst I installed that, I tidied the last of the wiring for the new ECU - only to find the ECU will not fit in the same place as the old one did, as the ECU plug (as I mentioned earlier) is much bigger than the old one! D'oh!

So I'll have to come up with a new place for the ECU to get attached to. Early thoughts are down in the footwell, but behind the panel I have that covers the fuses and relays.

The wings came back from Normandale last Friday, and look great, now the crazing has gone. No need to post pics as you know what they look like, but suffice to say they where true to the word and did me a deal - both wings repainted with the gel coat replaced, and new stone film on the rear wing was £145 + VAT. Considering they're not small items, I thought that was a damn good deal. :)

One last thing - I've also started on a major project to add power steering to Vikki. Taking a leaf out of another MOC member's book (Hi Lee!) I'm busy creating a electrically assisted column mounted system from an a spare E30 column and a Vauxhall Corsa power pack. It's quite involved, and needs several adaptors to be machined at engineering class - plus I shall be creating some custom electronics to give programmable speed sensitive assistance. Once I have everything ready, I'll post it up as a separate section on the site. 

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Reader Comments (2)

Re the idle. A couple of things.
1. Maybe the rev counter is wrong?
2. To test for air leaks you can spray fag lighter gas round the engine bay while the engine is running and listen for changes in revs.

I've just spent all evening reading this blog. Great work!


December 7, 2012 | Unregistered CommenterBen

Hi Ben,

I've checked the rev counter against my multi-tester that has a tachometer setting and its accurate.

I'll try the gas trick though. I've tried using carb cleaner in the past, but didn't find anything.


December 8, 2012 | Registered CommenterGOO

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