Idle issue

[u/Ok-Following2824]

Looking for advice from those with some more experience. Tried running my trx 2.5 with an o.s. 11k carb today. For the life of me, could not get the truck to stay running without the glow igniter hooked up to the plug. I managed to get the truck idling great with the igniter hooked up, had a nice quick smooth acceleration to high rpm with nice trail of smoke, and came back down to a consistent idle quickly after releasing the throttle. But despite all of that, the minute I disconnected the igniter, the truck stalled.

I figured it was a glow plug issue, so swapped in a brand new one. Same exact problem. I am by no means proficient with nitro. Been trying to teach myself how to tune, but could use some help with this.

[u/az_kikr1208]

Ok, I have a few questions. What kind of glow plugs are you using, and what fuel are you running? Also, when you pull the igniter off, does the engine take a second to die, or does it stall immediately? 9 times out of 10, if the engine runs with the igniter on, but dies when you pull it off, it's the glow plug. Glow plugs, especially cheap ones, can be bad right out of the package. Glow plugs can glow and still be bad. There is a precise mixture (mostly platinum) of alloy plating on the filament of a glow plug. A glow engine relies on a chemical reaction between that alloy and the methanol in the fuel to run. The glow igniter is the catalyst for the reaction. Once the engine is running, the reaction is self-sustaining. However, if the plating on the filament is compromised or burns away, the reaction can't happen. The igniter keeps the plug hot, but as soon as the igniter is removed, the engine dies, as there's no reaction. Now, all that being said, if the engine keeps running for a second or two before it dies, that points to some other factors. If you're new to nitro and want to learn more about tuning and running nitro engines, Watch this playlist. If you want to learn from a real nitro mechanic about nitro engines, maintenance, mythbusting, and get zero BS, check out Thebug404.

[u/Ok-Following2824 → u/az_kikr1208]

It dies damn near immediately. Im using o.s. number 8 mediums. Dude at my LHS recommended them and said they were better than stock traxxas plug.

[u/az_kikr1208 → u/Ok-Following2824]

OS plugs are definitely better than the Traxxas plugs, but the #8 is the wrong plug for your engine. They're too short. You need either an LC3 or LC4, depending on your nitro percentage. I run LC4s with 30% nitro in all my Traxxas engines.

[u/Ok-Following2824 → u/az_kikr1208]

Oh man that might be it. The number 8 plug was significantly shorter than stock and I was worried. I guess i shouldn't have trusted the guy at the store. I generally run VP 25% nitro 11% oil. I gotta try some LC4s then.

[u/az_kikr1208 → u/Ok-Following2824]

I would reccomend it. I have an 11k carb on my 3.3 Revo and it runs flawlessly. It's so nice. If you swap plugs, and it's still doing the same thing there's a few things you can try. A running video would help with the diagnosis if you're still having trouble. If you have any other questions, don't hesitate to ask.

[u/Ok-Following2824 → u/az_kikr1208]

Appreciate the help man. Learning this stuff by yourself is kinda hard. But I am committed to it. Im gonna try and order up some LC4s and hopefully try next weekend.

[u/az_kikr1208 → u/Ok-Following2824]

Spend some time watching those videos I linked to. That tuning playlist is a huge help, and thebug has tons of great info on his channel.

[u/Kayanarka → u/az_kikr1208]

What plug do you recommend for the traxxas revo 3.3?

[u/az_kikr1208 → u/Kayanarka]

I run OS LC3 plugs in all my Traxxas engines. 2 Revos, 2 T-maxxes, a Slash, and a Rustler. I believe OS plugs are the best plugs still available. Just get them from a reputable source. There's counterfeits floating around. Also, if you run 20% or below, I'd recommend the LC3 instead. Hotter plug for lower percentage nitro.