RB20DET refuses to run.

Thread in 'Technical Questions' started by StealthyGecko, Sep 22, 2020.

  1. StealthyGecko

    StealthyGecko Member

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    Hey all,

    I have a 1993 C33 Laurel with an RB20DET swapped in (the swap was done in Japan long before I got the car.)

    I am having a seriously frustrating issue with it.

    It was running better than fine, then, a few weeks ago I went to start it and it fell on its face. You turn the key, it starts and immediately dies again.

    I checked the ECU codes and got 55 (which as far as I have read means All clear) and when I unplugged the MAF it ran again but in limp mode (idles at around 2000rpm and won't go any further) initially and probably stupidly I took this to mean the MAF was bad so I got one from China (yeah, yeah I know!) didn't fix the issue, then I bought a genuine one from Garage D and initially thought it had fixed the issue but alas on the second startup it died again.

    I've read pretty much every bit of information on the internet about these symptoms and so far I've checked the timing, the CAS, the MAF (obviously), I've tried unplugging the cold start valve (no change). I've replaced the coolant temp sensor and I've upgraded to R8 coils so the stock ignition amp and wiring can't be the problem.

    At this point, I am at a complete loss, what to try next.

    If anyone has any suggestions for things to try next please shout out!
     
  2. r3k1355

    r3k1355 Well-Known Member

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    Have you tried unplugging the MAF and seeing if it will run? (with the 2000rpm limit)

    Could be a broken wire or something as well, which is a pig to figure out.
     
  3. StealthyGecko

    StealthyGecko Member

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    Yeah mate that was one of the first things I tried. It does run with the MAF unplugged like you say
     
  4. Tommy59

    Tommy59 Active Member

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    I would check the following:
    Throttle closing position, make sure it's open slightly
    Unplug IAC valve
    Unscrew the IAC valve adjustment screw until it's flush with the body of the IAC
    Unplug cold start valve
    Then give it a go

    If that somehow fixes it you can readjust your idle

    It won't spark at all if the CAS isn't working so you can probably rule that out

    Could be worth doing a vacuum leak test for peace of mind

    Failing on the above I would start hunting for wiring issues between the MAF and the ECU.
    Do you know which MAF it's running, i.e. does the replacement one match the original?
    IIRC R32 + R33 S1 - Green label, R33 S2 - Pink label, Z32 - Orange label
     
  5. StealthyGecko

    StealthyGecko Member

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    Thanks I’ll give all that a try and post the results.

    its an R32 (Green label) MAF
     
  6. StealthyGecko

    StealthyGecko Member

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    Sorry accidentally hit post before I’d finished ‍♂️ The MAF’s I’ve tried are all the same yes.
     
  7. BenRice

    BenRice Well-Known Member

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    Considering it runs without the MAF plugged in i think it's electrical

    Considering what you've said & the age of the car I would suspect it's something to do with the MAF wires (12V, grounds & signal)

    Check the wires at the MAF plug to see if any have broken. Clean the connections as well
    Check the MAF part of the loom for any points where it may have been damaged / melted
    Next check continuity between the MAF plug to the pins on the ECU plug. Best get a friend to help and slightly move the wires while checking continuity (to simulate the engine moving on start up / idle)
     
  8. StealthyGecko

    StealthyGecko Member

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    Thanks for your reply.

    I've checked the wiring at the MAF plug and cleaned the connections, but I do still need to trace it back to the ECU and check for breakages along the wire.
     
  9. StealthyGecko

    StealthyGecko Member

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    Okay, so things are getting a bit weird.

    I tried all your suggestions today:

    @Tommy59 i tried your suggestion and no joy which then led me to both your and @BenRice suggestion about checking the MAF wiring.

    continuity tested the wiring and all is fine also stripped the loom tape back to check for any potential breakages and there were none.

    so we plugged everything back in and tried testing the MAF itself I found a diagram of how to test a MAF but I didn’t have any spare wire knocking around so what I did instead was test it in situ.

    so I got the wife to try starting the car while I blew down the MAF, low and behold it worked!! Suddenly the engine ran, as soon as I ran out of breath it died again.

    so if anyone has any suggestions of what to try next please let me know,

    the fact that it works when I blow down the MAF makes me think something is stopping captain spooly from sucking air through.
     
  10. StealthyGecko

    StealthyGecko Member

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    Another update,

    So I’ve been out to the car again this morning, checked the turbo and it’s fine, spins freely and there is no play in the shaft.

    checked all intercooler couplings, there were a couple that could have been tighter and are now.

    checked the throttle body adjusted it a bit with the screw under the lever and it idled at 3k adjusted it back down and it wouldn’t idle at all it just died again. Tried to get it in between the two but still just wanted to die.
     
  11. BenRice

    BenRice Well-Known Member

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    Strange question, but how clean is the air filter?

    Will it run with no air filter on it?
     
  12. StealthyGecko

    StealthyGecko Member

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    It’s a HKS filter and I’ve literally just changed the filter in it, but throughout this troubleshooting it hasn’t even been fitted so in answer @BenRice it won’t run without the filter
     
  13. BenRice

    BenRice Well-Known Member

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    Cool. Can you add a picture of the engine bay?

    A picture says a thousand words & much easier to see if anything is out of place
     
  14. StealthyGecko

    StealthyGecko Member

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    @BenRice sure I’ll head out and get one first thing in the morning.
    , it’s dark here right now so kinda difficult to get one .
     
  15. StealthyGecko

    StealthyGecko Member

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    [​IMG]
    https://ibb.co/pLyfsH4
    Ignore the wiring on the right hand side I haven’t tidied it up after checking it all for breaks etc.
     
  16. BenRice

    BenRice Well-Known Member

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    BOV leaking? It's worth making a blanking plate and blocking off the BOV

    Unbolt the BOV, use the gasket to trace out shape on a sheet of aluminium and fit that between the BOV & the flange on the intake
     
  17. StealthyGecko

    StealthyGecko Member

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    Nah it’s not the BOV, I’ve already done exactly that to check that isn’t the issue.
     
  18. Tommy59

    Tommy59 Active Member

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    Is yours a sunroof model? I had a mates one that leaked out the sunroof drain tubes and we used to have to dry the ECU wiring loom out/ resolder corroded connections by the ECU every Spring as it sat in winter.
     
  19. StealthyGecko

    StealthyGecko Member

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    Nah mate, it’s a hard top.
     
  20. DarkDrifter

    DarkDrifter Member

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    did you check the Cold air start valve ?
     

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