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  1. #1
    Dunc is offline Tyre Kicker
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    Rover V8 low idle/rough running

    Took my Sumo for what was supposed to be a 20 minute blast yesterday and ended up with a problem! She started fine and I then took it easy for 5 minutes to let her warm up. Pulled into a drive to turn around and reversed out on full left hand down lock and heard a small clunk. From then the car backfired and ran rough until I got to a junction where I noticed the idle speed was down at 500rpm, normally it's 800. Then she stopped. And wouldn't start. Luckily it was outside a pub and the landlord was very accommodating! Eventually got her to start on jumps and she spluttered her way home, not happy. Today I popped her up on jacks and looked at whether going full lock LHD snagged anything. I checked all the leads onto the plugs and then fired her up and she started fine. She then idled fine for 10 minutes and so I stopped her, got her off the jacks and started her again. This time she started rough and had the same idle problem as yesterday with backfiring when I increased the revs. So I put her back in the garage.

    Any ideas?

  2. #2
    Sidecarbod's Avatar
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    More info required!

    What fuel system are you running? EFI, carbs? (what carb/s)
    What ignition system has it got fitted?
    I refuse to engage in a battle of wits with an unarmed opponent.


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  3. #3
    Dunc is offline Tyre Kicker
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    Sorry! Its an Offenhauser manifold with a 4 barrel holly carb. That, I'm afraid, is as much as I know at the moment. It's got optronic electronic ignition from S & S preparations I think.
    Last edited by Dunc; 03-01-11 at 08:21 PM.

  4. #4
    Sidecarbod's Avatar
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    Quote Originally Posted by Dunc View Post
    Sorry! Its an Offenhauser manifold with a 4 barrel holly carb. That, I'm afraid, is as much as I know at the moment. It's got optronic electronic ignition from S & S preparations I think.
    I'm afraid that I know nowt about Holley carbs! The problem could be due to carb icing. Do you have an insulator between the carb and the manifold?

    Your ignition could be at fault but since it is not an Opus jobbie I doubt it.
    I refuse to engage in a battle of wits with an unarmed opponent.


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  5. #5
    robcob's Avatar
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    Quote Originally Posted by Dunc View Post
    Took my Sumo for what was supposed to be a 20 minute blast yesterday and ended up with a problem! She started fine and I then took it easy for 5 minutes to let her warm up. Pulled into a drive to turn around and reversed out on full left hand down lock and heard a small clunk. From then the car backfired and ran rough until I got to a junction where I noticed the idle speed was down at 500rpm, normally it's 800. Then she stopped. And wouldn't start. Luckily it was outside a pub and the landlord was very accommodating! Eventually got her to start on jumps and she spluttered her way home, not happy. Today I popped her up on jacks and looked at whether going full lock LHD snagged anything. I checked all the leads onto the plugs and then fired her up and she started fine. She then idled fine for 10 minutes and so I stopped her, got her off the jacks and started her again. This time she started rough and had the same idle problem as yesterday with backfiring when I increased the revs. So I put her back in the garage.

    Any ideas?
    Start with the basic checks,
    is it getting fuel and is the pump working ok
    are the plugs all sparking
    plug leads all working
    check timing
    could be the power valve in the carb

    rob

  6. #6
    slogger's Avatar
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    Just a thought for what it's worth:
    If it appears to start and idle ok jacked up but shows this fault when on the ground, could the float level be suspect? Does the thing smell of fuel when it is running rough/black or grey smoke from the exhausts?

    Don't know what the connection to the clonk could be unless something mechanical is to blame.

    Just a thought as I said. Crystal ball fault diagnosis is always a bit suspect.
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  7. #7
    Dunc is offline Tyre Kicker
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    Amendment

    Thanks for the advice fellas. I re checked the carb on and its a webber 500 not a holly.... Getting to know the car slowly but surely. Anyone think this makes any difference?

  8. #8
    Dunc is offline Tyre Kicker
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    It does smell strongly of fuel, so I'll look at the carb. Could be carb icing too. Thanks again for the thoughts.

  9. #9
    Sidecarbod's Avatar
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    Quote Originally Posted by Dunc View Post
    Thanks for the advice fellas. I re checked the carb on and its a webber 500 not a holly.... Getting to know the car slowly but surely. Anyone think this makes any difference?
    I know a bit about the Webber 500.

    If you are sure that its going rich when the idle goes rough then its very likely just crap in the float valves. The weber is easy to work on, you can remove the top of the carb in about 5 minutes, the floats will come off with it.

    It would be worth posting up what fuel pump you have and whether you are running a fuel regulator. The Webber will not tolerate more than 6.5 - 7 PSI pressure. (Mind you if the pump pressure was too high it would flood all of the time)

    When you remove the top of the carb make a note of the hole that the accelerator link was in and remove the air filter stud to prevent ripping of the gasket. If you are careful you can re-use the gasket many times.
    I refuse to engage in a battle of wits with an unarmed opponent.


    Rules for buying 'Go Faster' parts:-

    If it's fast and cheap then it's not good.
    If it's cheap and good then it's not fast.
    If it's good and fast then it's not cheap!

  10. #10
    Sidecarbod's Avatar
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    Quote Originally Posted by Dunc View Post
    It does smell strongly of fuel, so I'll look at the carb. Could be carb icing too. Thanks again for the thoughts.
    Carb icing will make it run rough but not rich, just rough! I bet its just crap in the carb!
    I refuse to engage in a battle of wits with an unarmed opponent.


    Rules for buying 'Go Faster' parts:-

    If it's fast and cheap then it's not good.
    If it's cheap and good then it's not fast.
    If it's good and fast then it's not cheap!

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