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  1. #1
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    4Tec 3.3 Nitro stalling on idle

    I am having a problem with my 4Tec 3.3 Nitro stalling on idle. I fiddled with the adjustments by mistake and now it stalls on idle.

    High speed seems to be really good as the engine runs strong, does not stall on throttle, no hesitation and lots of smoke on throttle.

    But I am having a problem getting it to run on idle

    Any help is greatly appreciated

  2. #2
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    There should be a place for a flathead screwdriver, this will let you adjust the idle (increase/decrease idle rpm). I'm not quite sure specifically where this is but it should be on the carburetor. In really not a nitro guy but I home this helps you fix the problem, your manual should point you in the right direction. I attached a link to where you can download it in case you don't have one.

    https://traxxas.com/sites/default/fi...KC2075-R00.pdf

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    I already have the manual and the idle speed is not the problem.

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    Quote Originally Posted by tvr4 View Post
    I already have the manual and the idle speed is not the problem.
    Then I'm sorry, I can't imagine any other reason why it may run perfectly normal but not idle. I hope you find the help you need, just remember that the Traxxas forums is not really the place for this. You'd be better off contacting customer support or going to your local hobby shop.

  5. #5
    RC Champion grizzly03's Avatar
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    Quote Originally Posted by tvr4 View Post
    I am having a problem with my 4Tec 3.3 Nitro stalling on idle. I fiddled with the adjustments by mistake and now it stalls on idle.

    High speed seems to be really good as the engine runs strong, does not stall on throttle, no hesitation and lots of smoke on throttle.

    But I am having a problem getting it to run on idle

    Any help is greatly appreciated
    Have you tried setting the carb back to factory? That's the best thing to try when you lost where your settings are. It's possible your LSN could be rich.

    Quote Originally Posted by ElectricPropils View Post
    ...just remember that the Traxxas forums is not really the place for this. You'd be better off contacting customer support or going to your local hobby shop.
    What are the forums for? Sometimes customer support can help and other times they want you to send your items in. There is nothing wrong with asking questions on the forum because someone else could have had a similar problem and can explain what they did to fix.

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    I am of the same thought. The forums are a great place for many reasons. Primarily the reason you mentioned.
    I was wondering about resetting the carb to factory. I am going to do this today.

    The problem started during a run when the car stalled and refused to restart. A friend suggested I check to see if something got picked up in the fuel since I did not have a fuel filter (I do now). I removed the high speed needle and it was hard to blow in the carb line. I took a small wire and cleaned it out. Much better air flow now. But of course the setting is way off now.

    The next problem occurred during the adjustment process after. The ezstart stopped turning the motor over. I thought it had siezed. When I turned the flywheel be hand it spun freely and I felt compression.

    I removed the ezstart and it turned out that one of the two screws attaching the electric motor had backed out and stopped up the works. The other screw was loose and starting to back out.

    I put some thread loc on the screws, lubed the gears and put everything back together.

    Now I am ready to get it running again. Going to try resetting the needles to factory. I will update from there

    Thanks for the advice!

  7. #7
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    Quote Originally Posted by grizzly03 View Post
    Have you tried setting the carb back to factory? That's the best thing to try when you lost where your settings are. It's possible your LSN could be rich.
    Ok we are making progress. I set both the low-speed and high-speed needles to factory and it cranked up.
    But it still needs an adjustment but I am not sure what to change.

    IDLE SPEED - way to fast. I have to apply a lot of brake to stop the wheels from turning

    IDLE - will idle for a a short period but stalls

    HIGH-SPEED - Runs well, no lag on acceleration. On throttle I noticed fuel spitting from the exhaust.
    This is not the usual smoke but liquid fuel spitting out

    What should I adjust?

    Thanks !

  8. #8
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    Being Loaded up - before tuned it will spit liquid
    With High idle- adjust lsn to lower idle speed
    Lean condition on high idle would cause flame out

    HSN adjust adjust a bit rich at high rpm - holding full throttle

    Burn it real good
    fabricator

  9. #9
    RC Champion grizzly03's Avatar
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    If you didn't touch the idle screw from where it was when it was running good you can skip. Make sure your idle gap is around .8mm. If your idle gap is set wrong you can have trouble setting your LSN. I've used a normal sized paperclip to check idle gap before. (I think they are 1mm). Once set correctly you shouldn't need to adjust it anymore other than a slight adjustment when there is a noticeable change in weather.

    Then set your HSN. Make sure to do a couple of passes to check. Then adjust your LSN using the pinch test (2-3 seconds). Also do a couple of passes to check. If the HSN and LSN are set correctly and the idle is still too fast, then you can lower it with the idle screw.

    Make sure to run a pass each time you check a setting. If you don't it could give you a false needle setting. Especially since you are getting excess fuel built up in the engine.

    Traxxas tuning instructions for reference: support/Tuning-Your-Engine-Best-Performance

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    Thanks I will try this

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    Progress. It runs but needs some tweaking. I love the idea of using a paperclip to adjust the idle opening. It was open at least twice the recommended opening.

    I adjusted the idle gap, and ran it for a bit. I then adjusted the HSN a little to lean it slightly to stop the spitting out the carb.

    It runs ok but stalls after a while on idle and if I apply the brake for a prolonged period.

    Here is a short video the the idle stall
    https://www.dropbox.com/s/3pkbu81jka...Stall.mp4?dl=0

    Here is the smoke coming out the exhaust. I use a piece of clear hose to route the exhaust out of the garage
    https://www.dropbox.com/s/06neoj0u16...Smoke.mp4?dl=0

    What adjustment should I try now?

    Thanks!

  12. #12
    RC Champion grizzly03's Avatar
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    It looks like the idle is still high. You shouldn't get a change in engine RPM's when applying the brakes, it looks like the clutch is still trying to engage.

    Looking back through the thread you said you used a piece of wire to unplug something (carb line or HSN). You couldn't blow through the line?

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    Quote Originally Posted by grizzly03 View Post
    It looks like the idle is still high. You shouldn't get a change in engine RPM's when applying the brakes, it looks like the clutch is still trying to engage.

    Looking back through the thread you said you used a piece of wire to unplug something (carb line or HSN). You couldn't blow through the line?
    1) What should I adjust to lower the idle, LSN or idle speed screw?

    That is correct. I tried to blow in the fuel line and it was hard. So I removed the high speed needle and cleaned it out with a small wire. That cleared out whatever was in there and after that it was easy to blow in the fuel line

  14. #14
    RC Champion grizzly03's Avatar
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    I'm thinking the idle screw could be lowered. The paperclip would be a reference point to compare with. Mine are set slightly smaller than the paperclip. If the idle is set to high (opening to big) you will have trouble setting your LSN correctly.

    Could you have damaged the carb? The high speed needle works with a tapered seat where it screws in. What part did you need to clean out, the HSN banjo fitting inlet part or the carb itself?

    Here is a link to an exploded carb picture and rebuild info:rebuild-TRX-carburetor

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    Depends on how big/thick the paper clip is. The smaller ones run about 0.5mm which is too small for the carb. The larger one is around 1.0mm which is just right. I found one that is in the middle (measured with a digital micrometer) and use it to set the gap. I leave the gap and set the idle with the LSN.
    The Super Derecho

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    I will turn out the idle speed screw and start from there.

    I forgot to mention that the engine is difficult to start. Sometimes I need to crank it for a bit and work the throttle before it starts

  17. #17
    RC Champion grizzly03's Avatar
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    Do you prime the engine (priming fuel line to carb)? If there is air in the line it takes a bit to work it out by just turning it over.

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    Quote Originally Posted by grizzly03 View Post
    What are the forums for? Sometimes customer support can help and other times they want you to send your items in. There is nothing wrong with asking questions on the forum because someone else could have had a similar problem and can explain what they did to fix.
    The only reason I said that was because with problems like what he is having it is hard to solve the problem when you can't physically have it in your hands or when you have no images/videos of the vehicle in question. I definitely think that problems can be troubleshooted in the forums but it's really hard to solve problems when the (experienced) people that commonly browse these forums can't experience the problems. This is the exact reason that Traxxas frequently asks for you to send back your vehicle if you are having problems. It's the same thing with a hobby shop, usually the people that work there can diagnose a problem in a heartbeat once they get it in hand. When people don't really know what they are doing or what they are talking about it just creates a problem that can't be solved. But like I said, when you are experienced and are having problems that you have never experienced before with vehicles that you already work on and parts that you understand then troubleshooting is your best option.

    ps. I'm not saying that this person is uneducated I am merely stating that some of the people on these forums would benefit more from going to a hobby shop or sending their car to Traxxas. At the least people could attach a video or image to their post.
    Last edited by ElectricPropils; 10-19-2020 at 09:37 AM.
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  19. #19
    RC Champion grizzly03's Avatar
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    Quote Originally Posted by ElectricPropils View Post
    ...
    ps. I'm not saying that this person is uneducated I am merely stating that some of the people on these forums would benefit more from going to a hobby shop or sending their car to Traxxas. At the least people could attach a video or image to their post.
    While I agree with what your general point is, it's not going to work for everyone. There is the majority on this forum that are asking for guidance because they want to learn about their vehicle, and the satisfaction of repairing themselves. Or don't have the extra money to have someone else fix for them.
    IMO Those with the money to afford having their rc's fixed wouldn't be the ones asking for guidance, or continued troubleshooting with an issue.

    Then there is a whole other group of people that you are forgetting about. Those that are outside of the USA. They are not able to send back to Traxxas for repair. Traxxas will say (tell them) to get in touch with the distributor for their country. Being outside the USA has its own challenges. Other than seeking help from a forum their only choice is a local hobby shop, if there is any near them.

  20. #20
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    Quote Originally Posted by grizzly03 View Post
    While I agree with what your general point is, it's not going to work for everyone. There is the majority on this forum that are asking for guidance because they want to learn about their vehicle, and the satisfaction of repairing themselves. Or don't have the extra money to have someone else fix for them.
    IMO Those with the money to afford having their rc's fixed wouldn't be the ones asking for guidance, or continued troubleshooting with an issue.

    Then there is a whole other group of people that you are forgetting about. Those that are outside of the USA. They are not able to send back to Traxxas for repair. Traxxas will say (tell them) to get in touch with the distributor for their country. Being outside the USA has its own challenges. Other than seeking help from a forum their only choice is a local hobby shop, if there is any near them.
    I agree and understand your point. One more thing I would like to add is that if you are interested in learning about your vehicle then YouTube is probably the best place to start, of course you can come to the forums for questions about your vehicle but easily the best place to learn stuff like that is through a video where someone an point out every detail.

    When I stated that this guy was better off contacting Traxxas or going to a hobby shop instead of using the forums was because it seemed like his problem had more to do with his engine than he had the knowledge to handle, of course people on this foru can point it out but it would be much more efficient to have a experienced hand work on his vehicle and then tell him what they did to fix it.

    That's what I did for the first year of me getting into this hobby, then eventually I learned how to troubleshoot problems on my own.

    Something stops working
    I go to my hobby shop
    They tell me it may be because of _____
    In that moment I learn that because of ______ my car does ______

    Rinse and repeat until I start to learn things on my own and now I don't need help period. I understand this doesn't work in every case but it is good start to learning these things on your own.
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  21. #21
    RC Champion grizzly03's Avatar
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    Quote Originally Posted by ElectricPropils View Post
    ...When I stated that this guy was better off contacting Traxxas or going to a hobby shop instead of using the forums was because it seemed like his problem had more to do with his engine than he had the knowledge to handle, of course people on this foru can point it out but it would be much more efficient to have a experienced hand work on his vehicle and then tell him what they did to fix it.
    That's the reason for asking questions and trying to repair yourself, to learn and gain experience and knowledge. Being told what was fixed is different than knowing the steps needed for the repair.

    Quote Originally Posted by ElectricPropils View Post
    ...eventually I learned how to troubleshoot problems on my own....and now I don't need help period...
    I'm glad that your smarter and have more experience than everyone here asking questions or opinions. Even at 44yrs old I'm still learning new things when I ask questions. Technology is advancing at such a rapid rate there is always new ideas out there.

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    Quote Originally Posted by grizzly03 View Post
    I'm glad that your smarter and have more experience than everyone here asking questions or opinions. Even at 44yrs old I'm still learning new things when I ask questions. Technology is advancing at such a rapid rate there is always new ideas out there.
    I'm sorry, that wasn't worded right. I was trying to say that when it comes to problems with my RC I don't need help if something isn't working right. Obviously there are times when asking for other people's opinions is the best option, especially when it comes to getting advice on something you might want to do to improve performance, or really any aspect of your vehicle where experience preferred. When it comes to fixing stuff (such as operating problems) it is best to be knowledgeable in a subject. I don't know everything about the hobby and I'm sure no one does, but I know enough to solve any problem I come across. Sorry for any misunderstanding. You must understand that I am only 17 and I hold a much higher standard for adults.
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  23. #23
    RC Champion grizzly03's Avatar
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    Quote Originally Posted by ElectricPropils View Post
    I'm sorry, that wasn't worded right. I was trying to say that when it comes to problems with my RC I don't need help if something isn't working right. Obviously there are times when asking for other people's opinions is the best option, especially when it comes to getting advice on something you might want to do to improve performance, or really any aspect of your vehicle where experience preferred. When it comes to fixing stuff (such as operating problems) it is best to be knowledgeable in a subject. I don't know everything about the hobby and I'm sure no one does, but I know enough to solve any problem I come across. Sorry for any misunderstanding. You must understand that I am only 17 and I hold a much higher standard for adults.
    I understand fully. Your grownup more than most just by having this conversation. There is nothing better than having the ability or understanding of how to do your own upkeep in your hobbies or day to day life. This way if you wanted to pay someone for a service or repair you know what your paying for. These forums are a great wealth of info. Especially when you want to try something new. Wish I was rich to try all these ideas floating around here, LoL.

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    Quote Originally Posted by grizzly03 View Post
    I understand fully. Your grownup more than most just by having this conversation. There is nothing better than having the ability or understanding of how to do your own upkeep in your hobbies or day to day life. This way if you wanted to pay someone for a service or repair you know what your paying for. These forums are a great wealth of info. Especially when you want to try something new. Wish I was rich to try all these ideas floating around here, LoL.
    Me too, I have to work for everything I buy. Most hobby shops don't charge just to tell you what they think is wrong, where they charge you is the parts to fix it or the fixing it itself. You can often go to a hobby shop and tell the your car isn't working, they will then evaluate you car and tell you what's wrong, that's when they charge you to fix it and you just decline. That's what I did and I live 30 minutes away from my nearest hobby shop.
    The present is theirs; the future, is mine.

  25. #25
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    I tinkered with the adjustments again and it will not idle or run at low speed properly.

    I adjusted the carb slider gap using an old wire automotive valve gage.

    It runs good at mid to high speed. But idle is a major issue.

    I am going to replace the carb and go from there. The guy I bought if from really didn't know what he was doing and did not take good care of it. I saw other really poor repairs that I have fixed. Maybe this is a result of his neglect.

  26. #26
    RC Champion grizzly03's Avatar
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    Last question: I don't remember if it was asked what glow plugs you were using? Another thing to keep an eye on is your exhaust. Check for cracks in the header and exhaust coupler. They can cause weird tuning issues.

    I hope the carb fixes your problem as nitro can be a lot of fun. Good luck and keep us posted.

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    Sorry for not mentioning the glow plug. I am using whatever one that was with the stock kit.
    I don't know the part number off hand.

    Good idea to check the header and exhaust. I took it off a few times but didn't check it.

    You are right, nitro is a lot of fun. Love that nitro scream on throttle.

    I started with nitro on my first RC car many years ago. That vintage car sat in the attic for at least 20 years and only took a few cranks to fire it up. Plus it still runs great.

    I should have the carb later this week. I took the old one off to look at for now
    I will update when I install the new carb

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    Who hoo. Problem solved. It was the carb.

    I installed the new carb today and after a few cranks it fired up, runs well at idle.

    I only adjusted the carb slightly because it is considerably colder today (about 44 degrees F) than it has been (in the mid to high 50's F)

    The idle speed was way to fast so I lowered it. There is bogging and a lag on throttle but this gets better as it warms up.
    I don't want to tinker with it too much since it is so cold.

    What should I do with the old carb? The new one was only about $30. It it worth trying to rebuild/repair the old carb or should I toss it in the trash?

    Thanks everyone for all the help

  29. #29
    RC Champion grizzly03's Avatar
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    Awesome! Glad you got it figured out. Just a tune now and your back to fun.

    IMHO I would toss the old carb. I'm thinking something was damaged. (why go through this again,lol)

  30. #30
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    Quote Originally Posted by grizzly03 View Post
    I'm thinking something was damaged. (why go through this again,lol)
    I completely agree on that one. There is definitely something screwy with the old carb.
    Thanks

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    I am so fed up with this engine. It runs for a bit refuses to run for any length of time. A new carb and days of tinkering with adjustments refused to solve the problem.

    High speed has been good. It will not run on idle for more than a few seconds.

    Should I look into a rebuild? I bought the car used so don't want to sink a lot of money into it before the cost gets closer to a new vehicle

  32. #32
    RC Champion grizzly03's Avatar
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    Have you tried running it without the added fuel filter? I never had good luck with them, I stick to the ones already built into the fuel tank.

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    I ran it before without the added fuel filter. Same issue

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    I took the head off to take a look at the inside of the engine and I saw some dirt and debris of some sort. Not sure how it got there. It was way to much to just have sucked a little from the tank.

    The cylinder sleeve looked ok I think. There were no scratches on it.

    However the bell housing had a deep groove on the inside where the clutch shoe spring was wearing on it. The clutch shoes were worn really bad.

    Makes me think the guy I bought it from put LOTS OF MILES ON it. I only ran it a few times.

    What parts are needed to rebuild the engine?

    I know I need some external parts, like the clutch and bellhousing. But it those parts look that bad I bet the engine has lots of miles on it and may be in need of work also

  35. #35
    RC Champion grizzly03's Avatar
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    That's not good. Those shoes are quite worn if the spring was cutting a groove.

    If doing an engine rebuild myself, besides the piston/sleeve and new bearings I would also get a new connecting rod. The Traxxas Power-up program might be a better deal. https://traxxas.com/powerup

    Too see how worn an engine is (sleeve/piston) you would check to see how far up the piston can go. If it goes flush or past the top of the sleeve it's worn.

  36. #36
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    I am wondering if the clutch dragging was why it would not idle.

    The clutch spring had unhooked and was wearing a groove in the clutch shoes and the bell housing.

    I looked at the engine piston and it does not go all the way to the top. It stops 3mm or so before the top of the sleeve.

    I agree about the PowerPoint program. I would enjoy rebuilding the engine.
    But the piston & sleeve are about $70. This does not include anything else i may want to replace.
    The new engine under thevpower-up swap would only cost $115. I am going to call a local hobby shop and see if they have any in stock

  37. #37
    RC Champion grizzly03's Avatar
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    If the clutch spring was broke and/or the clutch shoes were dragging that is probably your source of idling trouble. It would seem that no matter how low you went with the idle the car would keep trying to move. I would try a new clutch and give it a go.

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    I completely agree. I bet that is why it stalled the other day. The clutch spring must have completely broken and the clutch was always at least partially engaged. That is why I could not get it to idle or get the wheels to stop spinning.

    I am going to the hobby store today for new parts to repair it

  39. #39
    RC Champion grizzly03's Avatar
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    Here's to hoping for the best. I'm optimistic that's what your trouble is.

    The pinch on your sleeve sounds like it still has some good life left in it.

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    I forgot to remove some parts when I traded in the engine and it was too late to get them back. So I had to order them.
    I could not find the clutch bell anywhere so I will have to reuse that.

    But this will delay the process a bit.

    I did get the clutch shoes. How does the spring and the clutch shoes get installed?

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