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MonkeyChap

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About MonkeyChap

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    http://

Profile Information

  • Location
    London

Previous Fields

  • Current 911
    1984 Carrera
  • Daily Driver
    BMW 116d ED
  • Lottery Car
    I'd buy my old 2.2S back
  • Favourite Food
    Bacon
  • Drink?
    Strong Continental Lager
  • Drive of your life
    my old 2.2S....sigh

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  1. Hi - it wasn't a dig - sorry if it came over that way. Looking at it now, it does look a bit salty. It was more of a comment on, as you say, 2 pages of thread and frustration with what on the surface seems to be a simple car. By the sounds of it, most people think this is a tricky one to diagnose, and the stuff on the web is pretty inconclusive. I think I tested each of the possible causes in order of most-likely / easiest to test without breaking anything else. The reason for me re-posting after everything I tried is that if these threads are going to be useful to anyone else in the future, knowing what worked in what order is what these things are about. I still don't know if it's the mixture, and if you can tolerate this thread getting any longer, I'll post again as I try the other things on the list. I'd planned to summarise the process at the end, just as I did with the lights and fusebox wiring diagram I posted a while back. Hopefully Ivan is right, and now someone's actually told me a) this adjustment screw isn't the one on the ECU (see earlier in the thread, it's the only thing that's mentioned) and b) only affects the idle fueling I can give it a go. It would have been pretty daft if I'd just gone and leaned up the mixture at idle only to go and hole a piston at WOT. Also, I don't have Ivan's ear (or aircon) for this so I'll need an AFR meter to do it (it arrives tomorrow). PS - I took the bypass valve off today and tested it. I also tested the old one again. As well as the shake test, and the resistance test, you can test it opening and closing with a 12v supply (I used a desktop current limiting supply - suggest you employ a fuse if you test with a battery). The centre pin is +12V the pins either side will open or close the valve as each is connected to earth. Don't connect both to earth at the same time - move your earth lead from one outer pin to the other. The valve will click open and closed. Anyway, long story short, it turns out I'd replaced a perfectly fine air bypass valve. Ian
  2. This is getting a bit silly now. Is this adjustment you're talking about just for the idle mixture ? Adjusting the overall mixture at idle, with no way to read Air-Fuel-Ratio sounds a bit daft to me, but what do I know. If it's going to affect the fueling map for the car across the whole rev and throttle range, I'll wait for the WB Lambda to turn up and have a proper look.
  3. The 8 position switch on the motronic ECU. I didn't even know there was a mixture screw on the AFM ! One more thing to tinker with. I assume it's not doing anything at idle though, as the throttle position switch will be closed ?
  4. Mine were cleaned by Redtek about 3000 miles ago. They also flow tested them, so it's unlikely. I've pretty much eliminated the air leak possibility. That leaves AFM, vacuum leak, dodgy idle switch, or fueling problem (e.g. injectors, over-pressure, etc.)
  5. I tried that. In the end I tried all 8 positions on the switch. None of them made the slightest difference. I'm now getting rather twitchy that this might be an overfueling problem (e.g. knackered injectors) and the cost that comes with that ! Lambda is on its way though, so I'll at least have an AFR reading to go off.
  6. Quick update - I sprayed carb cleaner around the base of each manifold leg. No change in behaviour. What is weird though is that the car was absolutely fine starting from cold yesterday. On the Motronic ECU there was no hunting, and the idle settled quickly down to 900rpm and held there. There was a bit of hunting with the CANEMS box plugged in, and the idle was very high, but nothing compared to the day before. The only real change was the weather - from overcast and rainy to sunny and dry. If the AFM had been a hot-wire job, or the whole thing was MAP I could see barometric pressure being a factor, but not with a flap sensor. I suppose the other change was that I unbolted the Motronic from the car floor as it was a bit of a faff constantly plugging and unplugging it. Can't see that affecting anything though. With the car running cold(ish) at idle, I tried adjusting the fuel quality switch on the Motronic. It made no difference whatsoever on any of the settings. @proporsche- the reason for buying a (wide band) lambda sensor is that it's cheaper than buying a gas analyser, and all the garages are shut at the moment. Also, with the CANEMS ECU, I can wire the sensor into the ECU and use it to control the fuel map at partial throttle and (maybe, not sure about this) at idle.
  7. Well...for an 80s car I think they've got a pretty convoluted air and vacuum system. Not to mention the two-bolt inlet manifold design on a head that's designed to run a bit hotter than a water cooled one. No AC, but I take your point about running too rich. It seems unlikely as the problem exists for two different ECUs with different maps in them unless the injectors are a getting a bit worn and dumping too much fuel for the car to cope with at low revs. Oh well, I'll put the Motronic back on tomorrow and twiddle the idle enrichment doo-dah just in case. Remaining candidates are.. 1) air leak at manifold gasket 2) vacuum leak to fuel regulators 3) running too rich at idle (might have to wait for the lambda to arrive for that one if the twiddling doesn't work) 4) AFM is buggered (after 129k miles this isn't that unlikely) 5) ...and I only just read about this one...as well as the throttle position sensor (open /closed) there is also a microswtich that activates on fully closed throttle. I hadn't even spotted that one, so maybe I'll check that out too
  8. Had time to tinker a bit today: * Fuel filter is only a couple of thousand miles old * Attaching the CANEMS ECU showed that the cylinder head temp sensor is working fine * ...and there was also hunting at idle with the CANEMS unit. It never dropped low enough to stall the car, but it did rev higher than the Motronic (up to about 1500 rpm at peak) * Throttle position sensor is working So it looks like there's nothing wrong with either ECU. I've swapped out the air bypass valve (the old one passed the shake and resistance tests). It's also unlikely to be a rich mixture problem as both ECUs are causing hunting. AFM seems an unlikely culprit as it shouldn't be playing any role at idle when the throttle position switch is reading closed. I guess it's possible i bought a duff bypass valve (new) but that seems unlikely. A few people mentioned air leaks at the inlet manifold gasket, but apparently they tend to happen when the engine is warm. I bought an old handbrake when the car was restored which has a manual throttle lever. I'm tempted to remove the whole bloody air bypass system and just connect in the throttle lever ! Ian
  9. Good questions. No idea if Nick put a new filter in when he restored the car - I assume he did as the tank was out. I probably changed it when I replaced the pump in 2013. It's only done a few thousand miles since then. I wanted to fit a wideband lambda anyway, so this is a good excuse to do it, and then I can set up the idle mixture.
  10. David's coil pack kit includes a blanking plate for the distributor. It's all currently removed from my car since the ECU blew. Unfortunately, Nick took out all the loom as as well so I've got a pain of a job to wire it all back in again now..including lift up freshly fitted salt and pepper carpet.
  11. Be careful with starter chargers and ECUs. I've got an early CANEMS ECU and they didn't have any circuit protection for higher voltage input. Nick put my car on starter charger after the refurb and blew the ECU. David at CANEMS was really good about it - not only did he repair it free of charge, but he added in the circuit protection features of the later ECUs.
  12. That's a good point - I should work through the possible issues one by one. I've already replaced the air bypass valve (which actually made it worse). I spoke to Wayne at Chip Wizards (the ECU is one of his) and he reckons the usual culprit is two transistors on the board that open and close the air valve and which tend to deterioate over the years. Easy job to fix, apparently. In order of likelihood (biased by how easy to fix) I reckon: 1) swap in the CANEMS box with a stock map on it - that'll tell me if it's an ECU problem or something in the air / fuel system 2) if the ECU is the problem, replace the transistors 3) check the cylinder head temp sensor is working (maybe do that while the CANEMS box is in, as I can see the result on the laptop) 4) adjust the idle mixture screw 5) swap out the AFM (may be go with a CANEMS one)
  13. Thanks - I don't have a gas analyser so is it just a case of suck it and see ?
  14. Cheers ! Presumably the other end of the tube is venting to air somewhere behind the front bumper ?
  15. My evap tank is long gone - I think it was an integral part of the washer tank ? Great big thing that sat under the wheel arch. The weird white plastic box and pipework is still there from the filler neck. No idea what to do with that !

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