Oh God another idle problem thread.

Discussion in 'Technical' started by Z-ster, Jun 18, 2007.

  1. Z-ster

    Z-ster Active Member

    Yes, another idle problem thread, however my idle problem is a little different from the norm (at least I think it is).

    Firstly a brief description: At 750rpm the car appears to idle ok, not perfect but ok. On the other hand at 1,200rmp it's really rough especially when cold. At normal operating temperature the problem is less noticeable. but it's still there.

    Here are a list of the checks/test performed so far...
    • Coil packs and PTU are hard wired (no connectors).
    • Injector connectors have also been cleaned.
    • A balance test was performed using Nissan Datascan and each cylinder was switched off one at at time. Each one had a noticeable, and similar, effect on the idle. This would therefore indicate no issues with either the coil pack, injectors or wiring.
    • The TPS has been checked for flat-spots on the variable resistor with Datascan and is behaving normally.
    • A boost leak test (to about 5psi) has been performed with no noticeable leaks present.
    Following the tests above I have concluded its not a electrically related problem.

    Last time I checked the TB's they were relatively clean so I don't think it's related to them. Not sure how such a thing could be related to the AFM but I guess that might be worthwhile checking too.

    I've now started thinking that this problem might be related to the exhaust manifold gasket, or a loose/broken bolt on the manifold.

    This morning when I started the car at 6:30am it sure did sound like it, even for someone who's not familiar with the sound. However the puzzling thing is why/how would the idle get better when it warms up?

    I've searched the forum and found some post relating to this manifold problem, just needs someone to verify if my symptoms sounds familiar and related.
     
  2. K-zed

    K-zed Secret Squirrel

    John, when did you last change spark plugs?
     
  3. Z-ster

    Z-ster Active Member

    Yeah I've done that too and a few other things which I've not listed like the engine temp sensor, CAS connector and I've also rebuilt the IAA Unit although the I haven't inspected the air regulator unit which sits just beside the IAA.

    Spark plugs were changed but I would think my balance test results would eliminate the possibility of a spark plug issue anyway.

    Next step might be to perform a compression test on all cylinders out of curiosity more that anything.
     
  4. pexzed

    pexzed Forum Administrator

    How about Caz's

    fuel damper issue, might be worth a check.
     
  5. Z-ster

    Z-ster Active Member

    It's something that crossed my mind but I don't see how it would cause my problem. The symptoms are different.

    I might PM a couple of members who had the manifold problem to see if my problem has similar symptoms.
     

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