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  1. #1
    RC Competitor
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    Oct 2012
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    erratic idle on 3.3

    i just put a brand new 3.3 in my tmaxx. got it broke in, tuned perfect [i think] runs real good. the problem
    is, when it comes to a stop it idles REALLY high, and is trying to lurch forward. i have adjusted the idle on it, have the gap set in between 0.07 to 0.10, and have hsp an lsp set good. lsp has about a 3 to 4 second pinch test on it. nice smoke trail thru out the throttle. i dont understand why its idleing so high. and the idle is pretty erratic too, kinda like its "missing"?? i have checked for leaks and its tight as a drum. brand new fuel tank with new lines. has a brand new clutch and clutch bell. ANY HELP would be appreciated. thanks guys

  2. #2
    RC Competitor
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    you can stop the lurching by lossening the slipper clutch- as for the erratic idle, that may be a whole different problem.

    Here are some instructions for the slipper clutch- http://traxxas.com/node/89088

  3. #3
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    ok. got the lurching fixed with the slipper clutch. anybody have ideas about the idleing problem? sorry guys, but i am a bit
    impatient, specially when i can't figure it out on my own. anybody?

  4. #4
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    one more thing...i had posted a couple days ago about what looks like clutch dust or very small black particles coming from the clutch/flywheel area. could it possibly be the front bearing on the motor? like i said earlier, it is a brand spanking new motor

  5. #5
    RC Racer
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    How much smoke is coming from the exhaust through out the rev range, sometimes the idle can be effected if its running to rich or lean on the LSN setting. Mine was similar a few days back after re-tuning, I had it to rich on the LSN & once I gave it a slight adjustment & leaned the LSN slightly, the idle started to get better, less fuel after a high speed run so it dropped back to a good idle and stayed there. I just made sure there was still good smoke & not getting to hot.
    REVO 21tm grunt & JQ Products "The Car" GO NITRO

  6. #6
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    The black particles could just be from the clutch feet engaging against the clutch bell and rubbing off. Check the LSN like ozziii said, and if you get the idle back down, you will need to tighten the slipper tighter to get good acceleration that your car isn't jerky.

  7. #7
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    so with my idle being high like that and sometimes dropping back down, does that mean LSN is set rich? pinch test comes away 3 to 4 seconds. yes ozzii, there is good smoke thru out rpm range, smoke trails off a tad at the upper part of the range, but is diffentely thicker down low and thru the mid range. thanks for the responses, anything else anybody can add would be appreciated.

  8. #8
    RC Champion
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    i would take the carb off and check for cracks in the housing between the high side needle and the screw on the end (right under the HSN. I have found 2 of my carb with those hiarline cracks in the within 3 weeks of each other

  9. #9
    RC Racer
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    As long as there is still good smoke & it doesnt trail off to much then it should be ok, to be safe you could richen the top end a small amount & if you have lots of smoke down low then you could probably lean the low end a small amount. That should even out the smoke trail through out the rev range & hopefully sort the idle problem Like it did with mine. I have mine set nicely again & it seems to be going well atm, lifting the front wheels easily on take off & even when rolling forward slowly, still producing good smoke & not getting to hot. Thats using a good quality 20% nitro fuel with 12% oil.
    REVO 21tm grunt & JQ Products "The Car" GO NITRO

  10. #10
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    check the temp of your engine , for erratic idle can be a sign of over-heating...

  11. #11
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    .....and over-heating is a sign of lean mixture = air leak

  12. #12
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    the idle is high right when i start it. temps arent to bad 240-260. little warmer then what i usually like it. but i contributed that to the high idle. the carb is brand new but gonna look at it more closely for cracks and possibly RVT around the horn.

  13. #13
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    took out my tmaxx earlier. after RVT my carb horn and going over it with a fine tooth comb for possible leaks. it was still idleing very high, but after it got up to running temps. i did notice when i was playing with the gap in the carb, that when i plugged in my battery to the reciever that the gap would open a little bit, but when i turned on my controller, the gap would go back to normal. i even had the gap almost closed an it was still idleing very high. i guess what i am tryin to ask is, after running till the temps got up to normal, could the linkage somehow be making the gap open slightly? i dont know what model # my maxx is, but it was bought brand new in 2004. it has the black tranny too. but it does act like it has a leak somewhere, but i do not know where to look next

  14. #14
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    I dont know proper terms so try to follow me here. You can adjust the servo's and how the linkages pull on the carb. it sounds to me that your servo is wrongly adjusted so that its neutral is not actually the engines neutral.

    also, did you adjust the idle screw? try just changing it while its running?
    I'm crazy, no really I am.

  15. #15
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    check around the cooing head theres a copper o ring i guess you could call it also check around the glow plug and exhaust outlet make sure theres an o ring oround the exaust port and the there should be a copper washer around the glow plug i lost my copper washer around the glow plug put a new one in and it wasnt overheating anymore

  16. #16
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    Erratic idle= air leak. Not always, but for the most part you can hang your hat on it.

  17. #17
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    Oct 2012
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    thanks for the replys guys. i did pull the motor and totally sealed everything up with black RVT. also, my servo was bad and my throttle linkage had a very slight bend in it that wasnt letting the throttle gap close all the way to were i set it. new servos all the way around ordered up and fixed the linkage.

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