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1998 D1 3.9 issues after replacement exhaust fitted

Discussion in 'It's A V8 Mate!!' started by kurgan, Nov 17, 2020.

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  1. kurgan

    kurgan Active Member

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    Guys, I need advice/help. Had a replacement y-pipe with cats and new lambdas fitted. When I now start the car it immediately revs to 3000 rpm for a few seconds then stalls. All that's been replaced is the exhaust.

    Any ideas?

    SWMBO is getting annoyed.
     
  2. discool

    discool Well-Known Member

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    Hi, ive no idea why the engine stalls, hopefully compatible lambdas are fitted and the electrical connections are okay ? Replacing the exhaust won't stall your engine. As u say u had it fitted the question is what else has been touched ?

    But with the high idle speed that is possibly due the engine is breathing better after fitting the Y pipe etc, and so the EFI ECU recognised this, as it does.
    Its something that I had on initial start after I fitted a Janspeed CAT back system, the revs went up to 2500-3000 for two minutes, then dropped back down to 1000 and then onto its usual 650-700 rpm as it normally does on a cold start, so the ECU readjusted and sorted itself out, that was 12 years ago and never missed a beat since.

    So if you can get your engine to run longer, at least a couple of minutes the high idle speed will drop.
     
    Last edited: Nov 18, 2020
  3. kurgan

    kurgan Active Member

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    Discool, Thanks. I'll put in some fresh go juice and see if I can get it to self regulate.
     
  4. Alex458

    Alex458 Member

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    I believe the 14CUX ecu uses unique lambda sensors which work the opposite way to most others.

    I’ve seen universal sensors used on these and cause heaps of running issues.

    Did you fit them or were they done by a garage?

    Also I would check that no vacuum pipes have been knocked off the intake plenum during the exhaust installation especially the brake servo pipe
     
  5. kurgan

    kurgan Active Member

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    I had them fitted at a garage initially, then I removed and refitted myself as I was unsure if they fitted correctly. But they're for a disco 1 not universal fitting.
    I have checked all vacuum pipes they look to be good.
    Should I change the plugs/filters?
     
  6. discool

    discool Well-Known Member

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    The air filter would be well and truly blocked if it was stopping the engine, black all over.
    The would still run even if s few plugs were faulty, not very well but still run.
    The ignition coil top connections are clean and tight? Iffy coil or amplifier maybe a suspect. Even the spider immobiliser playing up which is easy to bypass to test.
     
  7. Alex458

    Alex458 Member

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    I agree with discool in the fact that changing plugs or filters would just be a waste of time at the moment.

    The way I read your post is that it’s been into a garage to have the new cats and lambda sensors and now has this problem which it did not before, based on that I would be checking everything that could have possibly been knocked loose changing the Downpipes.

    coil connections, Maf sensor etc, they may have removed the intake hose to better access the downpipe bolts for some reason is this tight etc.

    Just have a good look over everything you can in detail and see if anything is a miss
     
  8. kurgan

    kurgan Active Member

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    Discool, no spider fitted.
    Air Filter is clean.
    I'll go over everything this week. Check connections and tighten clips.
     
  9. classic kev

    classic kev Well-Known Member

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    MMMMMMMM............

    A bit odd for sure. New cats and sensors shouldn't affect cold start because the ecu ignores the O2 sensors until the engine is warm (70deg.C or thereabouts). The high revs suggests possibly a stepper problem. I think I would start by removing and cleaning the stepper and checking it works, also check the bypass air pipe. I could not be persuaded the issue is related to replacement of the exhaust components.

    Hope that helps ya.
     
  10. kurgan

    kurgan Active Member

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    Any suggestion helps
     
  11. kurgan

    kurgan Active Member

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    UPDATE. I've got the car idling at around 780rpm. But when I drive it the underside of the car seems to vibrate and shudder, there's no silky smooth ooomph. It's not a wheel bearing vibration as they were replaced in August for MOT. Could I be needing a transmission fluid change?
     
  12. classic kev

    classic kev Well-Known Member

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    Check both prop shafts - UJ bearings are possible causes. Also check the transfer box output bearings.
    Did you find out what your idle problem was?
     
  13. kurgan

    kurgan Active Member

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    Yes it was a stuck throttle cable.
     
  14. classic kev

    classic kev Well-Known Member

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    Aaaahhhhh, one of them tricky technical problems then! I won't tell if you don't. Glad you got it sorted.
    Good luck with the vibration/shudder, I guess that won't necessarily be as easy to sort. Chin up keep smiling and all that!
     
  15. kurgan

    kurgan Active Member

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    UPDATE: ALL SORTED.
    It's going like a scolded cock.
    Found out that the bolts on the manifolds to the block had been slackened off (by the garage) for whatever reason. So they got tightened up.
    The cause of the vibrations turned out to be my centre silencer not being attached at one end with the rubber bung on its hanger so it was vibrating and bouncing on the flange. Grrr.
    Thanks everyone who suggested things.
    It's silent and idling perfectly. And when you put the foot down it has a really nice snarl.
     
    Speckydude likes this.
  16. Ratae

    Ratae Well-Known Member

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    Mayhem Garage?
     
  17. kurgan

    kurgan Active Member

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    Nah, I think it's more likely a mechanic that's more plug-n-play than diagnose and fix
     
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