KJET 8v to 16v swap

Discussion in 'Mk2' started by mk2.mitch, May 19, 2019.

  1. mk2.mitch New Member

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    I'm in the process of swapping out my 8v engine to a 16v ABF (that was swapped into a KR car before mine running KJET) I received it will all the KR loom, metering head etc, everything to get it running. Rather than hacking up my loom, I was planning on try run it on the stock 8v loom alongside the 16v electronic ignition portion of the loom as there is literally 2 wires to splice together (RPM wire) and a start/run power to power the ignition timing box.

    A couple of things that I've come across:
    1. The 8v runs a vacuum solenoid valve by the metering head and the 16v has a deceleration cut-off valve. Do these do the same thing? Can I plug my 8v loom into the 16v metering head?
    2. The 16v throttle body closed switch has a three pin plug whereas the stock 8v one had a 2 pin plug. All it is is a button switch to sense if the throttle body is completely closed so I can't see an issue splicing the 2 pin plug to the 16v throttle closed switch.

    I've wired it up as above to test and it will start and idle but when you rev it up, there is about a 2 second delay, it'll rev up to 3k then hold there and not drop back down. I'm thinking that there is a difference between the 8v vacuum solenoid valve and the 16v deceleration cut-off valve.
    Is anyone done something similar before or able to share some advice?
     
  2. rubjonny

    rubjonny Administrator Staff Member Admin

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    1. no, you need the ISV control unit to work both the ISV and the over-run cut-off valve. just leave the valve in place and unplugged
    2. as above for the idle switch

    to make it work on the 8v loom as you say, start by dropping the ignition loom on top. remove the isv, you could fit the 8v AAV in its place. wire the cold throttle enrichment valve into the 'throttle open' side of the 16v idle switch, jobs a goodun.

    the valve on the strut tower is an increased idle control valve, you can run this on the 16v I guess just need to plumb it into the vacuum system. the 8v one is kinda inline with the AAV so you can replicate the same on the 16v
     
  3. mk2.mitch New Member

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    Cheers for you advice rubjonny. I decided to just drop it all the 16v loom. After finding out the guy I brought off had some of it labeled incorrectly so I've crawled through wiring diagrams to get everything wired up to the right place. I still can't get it to idle though, it just dies. When cold, it has a slight hesitation before revving up but once warm it revs pretty smooth but still wont catch idle.

    I did originally thought it might have been the ISV due to it not vibrating too much when you put your hand around it. I stumbling upon a spare that I found on a junk 8v engine I had lying about (which I'm not too sure why it was on that engine cause I though the 8v and 16v ones were different) but not this one hums and vibrates heaps so it must be working now.
    I've been tinking around with it for a few weeks now but haven't made any more progress and have gotten stuck.

    The only other thing that I think it could be is the guy I got it from likes to tune out the cold start injector so the mixture on the metering head has been turned 1 1/8 as he said. I have tried to run it with the cold start injector unplugged though which makes me think it's not that.

    Anyone have any other ideas?
     
  4. rubjonny

    rubjonny Administrator Staff Member Admin

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    the cold start injector will only spray fuel when cranking cold, once engine is started it doesnt do anything. So I'm not really sure what he is thinking messing about with the mixture to tune it out?

    Have a read thru my 16v troubleshooting guide as well, make sure all the basics are good:
    https://clubgti.com/forums/index.ph...air-and-tune-your-mk2-corrado-1-8-16v.195423/

    could be the over-run valve is broken or has fallen off, or the idle switch not quite working as it should. if everything checks out then get the base idle and co tuned hopefully that should do the trick :)
     
  5. mk2.mitch New Member

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    I thought it also sprayed under open throttle as well?

    I've gone through most of the stuff in your guide but not setting the base idle.

    I believe the over-run cutoff valve is operational as the revs do slowly drop as they're meant to if it is working and I've tested the idle switch which seems to be outputting correctly when pressed/de-pressed.

    Guess the next thing for me is to run through your guide however, my logic was that if it's all come out of a running vehicle, it should just work
     
  6. rubjonny

    rubjonny Administrator Staff Member Admin

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    Thats true yes but only when the engine is fully stone cold, the engine will cut off the thermoswitch pretty quick after the engine is started

    hopefully a slight tweak of the base idle should sort it
     
  7. mk2.mitch New Member

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    UPDATE: so I got the car to run and went for a drive today. I unplugged the vacuum from the over-run cutoff value and vacuum switch and wound out the idle screw and it it idled(a bit low but it did idle) it also appears that the ISV controller might not be doing anything apart from making the ISV buzz cause you can unplug that compactly and there is no change in how the engine runs. Also I tested the over-run cutoff value as per rubjonny's thread and it did not click so that might be dead although that shouldn't effect the idle?
    Is there any way to test the ISV controller/relay box thing?
     
  8. rubjonny

    rubjonny Administrator Staff Member Admin

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    try unplugging the 2 pin plug from the over-run cut-off, see if that helps

    with isv box check the idle switch next you should have ignition live on the black wire, when throttle is closed you should see 12v on the black/yellow wire this is idle switch closed feed to the ecu and isv module, also test for voltage on this wire at the module socket to make sure theres no issues in the loom
     
  9. mk2.mitch New Member

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    In plugging the over-run cut-off valve makes no change.

    I've checked both those things on the wiring and it all checks out fine.

    I forgot to mention in my previous post. To get it running I couldn't match up all the timing marks and remembered when I got it the cam timing was advanced a tooth so I advanced the cam timing a tooth but the distributor still wants to advance more and I can't time the flywheel mark.
    It's only just idling when hot and runs real rough when cold so my money is still on the ISV controller/relay box as I'm not convinced it's doing anything. You can unplug the whole controller and nothing changes...
     
  10. rubjonny

    rubjonny Administrator Staff Member Admin

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    may be worth going back to basics then. take the rocker cover off and check the intercam marks vs sprocket mark and cam lobe positions, check piston 1 is really at TDC when crank pulley marker lines up (ideally use flywheel mark if you can) if your distributor runs out of adjustment something isnt right, make sure its a genuine bosch unit as the cheaper aftermarket brands sometimes aren't made properly

    for isv module check all the pins for the required feeds at the box. ignition live at the back, earth at brown/white. black/yellow should have 12v when throttle shut, green/red should see sensor resistance thru the temp sensor on the head, figures for sensor resistance are in my guide. could open it up see if any obvious damage inside while you're messing about
     
  11. mk2.mitch New Member

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    So I'm made some more progress over the last few weeks.

    As you said rubjonny, I checked all the timing points and manually found TDC etc to make sure everything is all lined up where it should be.
    I've currently got it running with the idle screw wound out or just running (500 rpm) with it wound in with the overrun cutoff value vacuum line disconnected. As soon as you connect it again, the car stalls.

    At this point I think I need to get my hands on a replacement overrun cutoff value and also a CO meter so I can tune the mixture correctly and get it to idle better.
    I ran some throttle body cleaner through it and it seemed to 'unblock' it a little but my guess it it's either stuck open or closed and throws off the vacuum loop.
     
  12. rubjonny

    rubjonny Administrator Staff Member Admin

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    when I say unplugged on the valve I mean the 2 pin plug disconnected rather than the vacuum line, mine have failed electrically rather than mechanically
     
  13. mk2.mitch New Member

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    Oh yeah, I tried that too. Unplugged the connector car dies instantly. Unplug and cap the vacuum line and it starts and idles. I managed to find a replacement off an Audi 100 so hopefully this works otherwise I might have to resort to paying an eBay price. It was $10 be local so I took the gamble. 035133985a
     
  14. rubjonny

    rubjonny Administrator Staff Member Admin

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    not sure if that will fit, its listed for passat? the 16v one is 027133985A

    worst case remove it entirely, block the 2 hoses and plug the vacuum line till you fid one. all it does is catch the revs if you lift off at high rpm, as long as you're on top of it you can adjust your driving to suit short term
     

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