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Revo 3.3 Engine Idles way too High...HELP

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J

Jrizzle06

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  1. Bashing
So I've already broken in my Revo and am almost done with my Second gallon of gas.

Right now I have good acceleration off the line with lots of blue smoke and good top end with a nice stream of blue smoke as well.

The engine seems to run pretty cool as running temps were between 180-210 degrees. Seems like it should be a little hotter.

So everything besides the cooler running temps is fine but when I bring the Revo in to a stop, it begins to Idle very high, even starting to run away slowly. The temps will also start to rise and the engine gets louder. At the worse point you can hear a bunch of popping and clattering.
I tried turning down the Idle by turning the screw counter-clockwise but that only seemed to make the situation worse.

I can never get this thing to Idle right. It runs fine, it is just with the Idle. I will try to get a video up so I can show you guys what is happening. I also added a MS filter recently if that has anything to do with it. Everything else is stock for now.

There is something about Throttle trim and holding the break when you adjust the Idle? Maybe I should have been doing it like that and what does throttle trim do exactly?

It was a pretty cool day today 70 degrees with 75% humidity.
 
If everything is running as good as you say, but at idle the RPMs start to wander and heat up, it's a pretty sure sign of an air leak in the system.
 
That's what I was thinking, but I don't want to believe it. I think it may be from the lid of the fuel tank. I always had my doubts about it. Isn't there a way to adjust how tight that seal is by turning a screw. I will need to consult the manual on that.
 
Sometimes there's a center screw that will compress the seal, but there's always the possibility that it's worn. Always press down on the lid after refilling just to make sure it's tight.
Replace your lines and check the tank seal first. If nothing changes, you'll need to seal the back plate and carb neck.
It's really not a big job, but it's definitely worth it to get a good running engine running even better.
 
I will look into the threads about checking for air leaks.
What is the popping and clatter noise I hear? Is that Detonation?
 
Not really sure since I can't hear it first hand, but it could be pre ignition from a too hot engine, or just the clutch shoes expanding out from the higher RPMs and hitting the CB.
 
I am no expert but I would richen the low speed 2-3 hours and lean the high speed an hour and see if anything improves.

Remember Rolex is Da Man but I have found running the bottom richer and the top leaner than I was in the past has really improved general running of the 3.3.

Factory settings are 4 turns out on top and 11/2 -2 out on bottom(i thinks its flush)
 
So far I've replaced the fuel line. The idle has gotten even worse. Most likely from a bad tune, because before i realized it could be an air leak (First Post) I was messing with the needles trying to correct the Idle. So I should reset back to factory and go from there.

If it is not the line, then I think it may be the fuel tank lid. Is there a complete How To: Air Leak thread?

It is possible it could be a seal on the block issue or something. Cause when I was on my 10th tank of gas I managed to flip the Revo pretty nicely and got a nice scratch on the engine head from landing right on it. So that might have broken whatever seal there was. My Rear Left Upper Suspension Arm had broke also (Replaced with RPM Arm).

Edit:
I've probably flipped the Revo at least 4 times in its life
 
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Yes always start from stock settings after discovering issues with engine. The fuel tank lid replacement kit is pretty straight forward kinda hard to get it wrong. Another option is just get a new 150cc tank for 15 bucks and get rid of the older 125cc tank.
 
When tuning, keep in mind that whenever you adjust the LSN, it can affect how the engine idles. Even the small adjustments can make it idle higher or lower. Let us know what you find out.
 
MrClean said:
When tuning, keep in mind that whenever you adjust the LSN, it can affect how the engine idles. Even the small adjustments can make it idle higher or lower. Let us know what you find out.
Click to expand...

That was gonna be next target he might be to lean on the lsn. If it really jumps to life real quick when you go for the throttle then try richen it a bit. I would richen it until it seems boggy off the start then slowly lean it out till its at the point where it doesn't bog. Since I am now fully awake taking in account of your temps and the MS airfilter which will let it breath a little better this is the approach I would take. My revo is barley even thinking about grabbing second gear unless its 200 degrees or better. I really believe you are way to lean on the lsn which would explain it being so quick and high idle, your temps are cool because once you open it up it gets more fuel allowing it to stay cool. But I bet if you left it sit idling your temps would sky rocket.
 
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Update

So I've replaced the fuel line and still have the High Idle. I am going to test the tank right now.
I also just bought a new glow plug to use after I check out the tank.
When putting in a new glow plug; What direction should the washer be facing? Concave side up or Convex side up? I am thinking maybe when I last replaced the GP I may have put the washer in upside down, therefore making an imperfect seal. Any thoughts?
 
How would you seal up the back plate ?

I have a new 3.3 engine in my revo... I have about 9 tanks on it counting the breakin.. It is running lean on the bottom. The only way to get it to idle and not go screaming up a tree is to have the LSN at about 2.5-3 turns out... Other than this the engine runs fine. It starts great and has plenty of juice. However,,, When i richen it up is chokes out and stalls unless i'm alway into the throttle hard... I know its a leak. but I have ruled out the tank, seal and lines... Its gotta be somewhere else... I never removed the carb from the new engine. its still the facotry seal.

Any suggestions...
 
You'll need to try sealing around the carb and backplate both. It's not too difficult, get some high-temp sensor safe RTV. I'd recommend searching YouTube and watching someone seal one first, it helped me a lot.
 
thanks,

I'm going to seal it up today... I am just disapointed that a brand new engine would need sealing up... I wouldn't expect any new RTR truck not to run right, so I also expected my factory built engine to run like a champ right out of the box.

Is it normal to have to seal up a brand new engine ???
 
MadKawi is in the same position I am. I have replaced the lines and checked the tank, so now I am left with the Block. I noticed that around the seal is a little amount of dirt/grime which leads me to believe that is where the leak may be. Does that sound right? I tried to take pictures, but it is too hard to see the black stuff on the seal.

My truck is only a month old and I have an air leak. Now I just need to find the time to seal up the backplate.

I have to do more research before I go taking apart my block.
 
Jrizzle06 said:
MadKawi is in the same position I am. I have replaced the lines and checked the tank, so now I am left with the Block. I noticed that around the seal is a little amount of dirt/grime which leads me to believe that is where the leak may be. Does that sound right? I tried to take pictures, but it is too hard to see the black stuff on the seal.

My truck is only a month old and I have an air leak. Now I just need to find the time to seal up the backplate.

I have to do more research before I go taking apart my block.
Click to expand...

Use the exploded views of the motor, they are on the Traxxas website, they helped me out a lot in the beginning. If you have access to a printer that will do 11" x 17" printouts, it makes them even easier to read.
 
Got everything all sealed up and took the truck out for a run around the yard... It would idle perfect but when I gave it throttle it would totally crap out like it siezed as soon as the revs came up a bit...

Turn out it was the Glow Plug,,, Put a new one in and it runs like a champ...

Anyone out there who is frustrated with the way there Nitro engine is running, Try a new glow plug. I had no idea they would make such a difference.
 

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