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Thread: CA High idle, bogging down & flooding

  1. #1
    Guest TomB's Avatar
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    CA High idle, bogging down & flooding

    Ok, so have searched all the above issues and not been able to find anyone who's had the same combination of issues as me.
    I think the issue is either going to be a boost leak, AAC problem or knackered walbro.

    So.. it started a few days ago when I went to pull out of a junction and it bogged down and missed until the revs climbed and it really came on boost. Was fine when on boost above around 3k. Noticed shortly after that the idle was at around 1500rpm and the engine was warm.

    Managed to get some time yesterday to check under the bonnet, went through all the boost hoses and couldn't see any obvious issues, so thought i'd start her up and try and listen for anything obvious.
    That's when she wouldn't start , quickly noticed the smell of fuel so obviously flooding. Left overnight as it was getting late, and this morning fired after a few turns.... took up the rd, idle still high and quite lumpy while cold.
    Got home, turned off for 30 mins, and went to start again... and nothing, just the smell of fuel again.

    At first, suspected the Walbro was shot. It's about 8 years old and hasn't covered a lot of miles as the car has spent a good time off the road. But I'm not convinced that would cause the idle to be too high.
    I haven't checked the AAC yet, so will tonight... and at the same time clean the MAF.
    Is the CAS something that breaks down commonly?
    K&N is old and dirty, so i'm going to replace that too.

    After some advice really, as to what could cause that combination of problems... until the flooding problem, I was convinced there was a pesky boost leak somewhere.

    Spec:
    Stage 2, Norris designs Chip, Hybrid T28, Apexi AVCR, FMIC, Walbro, K&N, Oil catch can. Running fine for years, and nothing changed recently.
    Last edited by TomB; 08-12-2015 at 07:44.

  2. #2
    Dorset & Hants Rep pointz's Avatar
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    I would do a proper boost leak check and check all your vacuum lines! Has the hot start solenoid been removed?

    Boost/big vac leak willcause rich idle and the bogging down.
    Last edited by pointz; 08-12-2015 at 09:29.
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    Guest TomB's Avatar
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    Sorry forgot to mention that it's had the hot start solenoid bypassed already.

    Used to be able to do a boost leak test on the 300ZX by fitting a plug in the inlet with a tyre valve in it, pressurise the system and listen for a leak. Not sure if you can get them for CA pipework though?

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    Guest R3K1355's Avatar
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    You have to make one up yourself, although running that bad you can just spray some WD or easy start on the joins and see if the idle woddles around.
    It's also worth checking the timing, the splines in the CAS and camshaft wear and cause the ignition timing to get all ****ed up.

    Pull any ECU fault codes as well, sometimes that helps.

  5. #5
    Guest TomB's Avatar
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    Ok, so this seems to be caused by a combination of two things..

    1. The hose between the turbo inlet flange and AFM had worked loose slightly at the turbo so unmetered air was entering the system.

    2. The AAC seems to be fookered, as with it plugged in the car floods on starting. If unplugged starts easily and runs fine. When driving the car, it comes on boost smoother than it has done for a long time. If plugged back in while running the revs climb and it goes back to idling too high.

    Looks like service or replacement of the AAC it is then.

  6. #6
    Dorset & Hants Rep pointz's Avatar
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    Have you tried adjusting the idle?

    Give the iacv a good clean as it could be sticky, it's fairly easy to clean out tbh.

    I have a spare should you need one let me know
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    Guest TomB's Avatar
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    Nice one, cheers...haven't tried the idle. Don't think that could cause the over fuelling though?

    Starting to think that the AAC is amplifying the problem, have run it disconnected today and it's still running far too rich.
    Had to start it with the fuel pump fuse out, and at low rpm there is still hesitation.

    Even at low throttle the boost is very strong, and I couldn't find any boost or vac leaks.

    So, need to start narrowing down part's that will cause it to over fuel. Got a suspicion the AFM is the culprit.
    Will clean the IACV, AFM and throttle body out at the weekend.

  8. #8
    Dorset & Hants Rep pointz's Avatar
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    I would be checking timing and condition of cam and cas splines aswell mate
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    Guest TomB's Avatar
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    So, checked splines.. all good there. Cleaned AFM, and IACV. No change.

    Ran it and disconnected the lambda when running, zero change. Would have expected a drop, or even rougher running?
    Or will that only really happen when cold?

  10. #10
    Dorset & Hants Rep pointz's Avatar
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    Have you got a timing gun?

    Did you adjust the idle? You need to disconnect the electrical connector, adjust idle, then re-connect. (The revs should rise then settle when plugging it back in)

    Also have you tried self diagnosis on ecu? Could be worth a shot as may be temp sensor etc
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    If the lambda was screwed you would expect it to run smoother unplugged.

    I often unplug when I suspect it to be faulty and it drives nearly as well without than with....a little richer but that's it.

    Having said that every time I have had a lambda fault it has shown different symptoms,, ranging from mid revs misfire to hunting on idle.

  12. #12
    Guest TomB's Avatar
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    Quote Originally Posted by pointz View Post
    Have you got a timing gun?

    Did you adjust the idle? You need to disconnect the electrical connector, adjust idle, then re-connect. (The revs should rise then settle when plugging it back in)

    Also have you tried self diagnosis on ecu? Could be worth a shot as may be temp sensor etc
    Unfortunately I don't have a gun.

    It's clearly overfuelling like crazy from startup, as I need to remove the fuel pump fuse to get it started.
    If I don't it stinks of fuel when I crank it.
    From cold it starts on the key, but once it's run for a few mins I need to pull the fuse to get it started.


    Haven't touched the idle, as It's been fine for the 10+ years I've had it and I thought it unlikely to have changed.

    Will give the ECU check a go next, changed the temp sensor a few years back with a brand new one. If it's that though, nice easy fix!

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    Guest TomB's Avatar
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    So this turned out to be a faulty ECU temperature sensor, on removal it had a layer of crap covering half of it.
    Had ordered a new one, so replaced it and it runs sweeter than ever before. Making me think that it's been faulty since i've owned the car!

  14. #14
    Dorset & Hants Rep pointz's Avatar
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    Quote Originally Posted by TomB View Post
    So this turned out to be a faulty ECU temperature sensor, on removal it had a layer of crap covering half of it.
    Had ordered a new one, so replaced it and it runs sweeter than ever before. Making me think that it's been faulty since i've owned the car!
    Awesome! Cheers for posting back with the cure
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    Quote Originally Posted by TomB View Post
    So this turned out to be a faulty ECU temperature sensor, on removal it had a layer of crap covering half of it.
    Had ordered a new one, so replaced it and it runs sweeter than ever before. Making me think that it's been faulty since i've owned the car!
    did this throw a code or not?

  16. #16
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    No code, ECU test showed 55 no fault.

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