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Cold start and rough idle

Todom711 Jan 9, 2018

  1. Todom711

    Todom711 New Member I am in united_states

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    hello everyone,

    I just picked up a 92 FJ80 and she is a little on the rough side but side runs and drives like a tank. The issue i noticed is when the truck is cold starting it can be a little challenging it definitely has some hesitation. Also I noticed it has a little bit of a rough idle not too bad but you can tell its not normal especially for a yota. Any thoughts on what the issues are? Any feedback will be much appreciated.
     
  2. Ben Stratford

    Ben Stratford Well-Known Member Supporter I am in england

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    Hello Todom711,
    An excellent acquisition that you have there. Tell us a few more deatils to help us help you. Presumably it is a gasoline engine? Has there been any recent service work? Where abouts are you stateside?
    Welcome to our group. We love pictures and demand at least 1 every post!! Lets see the beast.
     
  3. Todom711

    Todom711 New Member I am in united_states

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    Hi Ben,

    yes its the 4.0 L 6 when i try to crank it from a cold start it seems to have some hesitation to it. for example the engine will turn over a few time and i have to turn it on and off a few times before it starts to run. It kind of reminds me of an old carbureted engine.

    IMG_3237.JPEG
     
  4. Ben Stratford

    Ben Stratford Well-Known Member Supporter I am in england

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    I dont know much about your specific engine but there are some petrol cruiser owners around.
    But the general things would be to get fuel air mixture to the spark at the right time with sufficient compression. So check the easy things first. Charge the battery up. Check spark plug gaps and ht leads are sound. Not sure if there is a distributor or not? Clean out air filter if necessary. Remove no1 spark plug and connect to ht lead and position the plug s couple of mm from block. Get somone to crank and see if the plug sparks to the block. If you have a strobe look at ignition timing. How does it run when the motor is warm?
     
  5. clivehorridge

    clivehorridge Well-Known Member Supporter Guru I am in romania

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    It’s worth starting her up in the dark, my experience with lumpy idle on a petrol was almost always traced to High Tension leaks.

    If it looks like a disco party in the dark, you’ve got some leakage which can usually be cured with new leads / spark plugs / or damp inhibited sprays.
     
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  6. Todom711

    Todom711 New Member I am in united_states

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    Thanks for the input. I will give it a try and when its warm it runs like a champ. It's really that cold start that's a issue.
     
  7. StarCruiser

    StarCruiser Well-Known Member Guru I am in uk

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    As Clive says, if you've got aged leads, distributor and rotor arm, replace the lot, it's not much money. If plugs haven't been known to be replaced, replace them first WITH THE CORRECT ONES FOR THE VEHICLE in NGK (what else) and start from there. If none of it makes any difference then at least you've eliminated that whole side of it.

    The other way is to do as Clive has said and spray a fine mist of water on the leads and dizzy cap when it's running well. If it begins to falter then you've got lead/dizzy failures which is often caused by poor plug gaps increasing doarkbvoltage and stressing and breaking down insulation.

    Another area to look at is intake hoses, check them carefully and thoroughly for splits. I've herd of puffing lighter gas around such things with the engine running and listening for a rise in revs but you obviously have to be careful you don't lose your eyebrows if there's any sparking going on with the HT leads (see above :) )
     
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  8. frank rabbets

    frank rabbets Well-Known Member Supporter

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    Sounds like the mixture is not rich enough for a cold engine. I assume mixture enrichment is automatic but that is what needs looking at. Check those items suggested as well though. In addition you can check each cylinder in turn by pulling off the lead to each and see if the roughness gets worse or stays the same.
     
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  9. clivehorridge

    clivehorridge Well-Known Member Supporter Guru I am in romania

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    With you on that Frank, if its not sparks its fuel, or vice versa.

    I know nothing of the 80 petrol, but I’m guessing fuel injection, not carb?
     
  10. frank rabbets

    frank rabbets Well-Known Member Supporter

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    Might be time to look at the WSM Clive :).
     
  11. frank rabbets

    frank rabbets Well-Known Member Supporter

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    Might be time to look at the WSM Clive :).
     
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  12. clivehorridge

    clivehorridge Well-Known Member Supporter Guru I am in romania

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    Nah, it’s usually the last place to look :lol:
     
  13. IRLGW

    IRLGW Well-Known Member

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    following on from franks suggestion, it could be the engine temp sensor. If its not sending the correct info to the ecu then maybe that is sausing the fuel mix to be invorrectly monitored. does it run oxy sensors in exhaust?
     
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  14. Todom711

    Todom711 New Member I am in united_states

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    i believe it does. It is EFI after thinking about it it sounds like its not getting enough fuel on the cold start. I am going to try these recommendations this weekend and see what happens.
     
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