I have a Revo 3.3, Futaba 3PL 2.4 ghz system, Duratrax failsafe, and a Futaba throttle servo. I was messing around on the street last night and I noticed some throttle glitches, I thought it was due to low voltage in my radio, the display said 5.0V. This afternoon I changed the batteries in the Radio and the same thing happened, but worse, the throttle servo (and only the throttle servo) would flutter very frequently and multiple distances and some times go to WOT. It seems to only happen when the engine is running. The receiver pack is charged (Maxamps 1600mv).

What normally causes glitches and how can I diagnose the faulty part (radio, receiver, failsafe, or servo)?

Would either be a problem with the Servo itself or your battery

Cheers

Ok, the battery is brand new, the servo is actually quite old.

One more note, I held the kit in off the ground and snapped the throttle a few times and it started to flutter really bad, I shut the radio off to engage the failsafe, the red light on the failsafe came on, but the servo stayed at WOT. I had this failsafe for a few months, and it's worked just fine. I had to pinch the fuel line.

Whats the best way to diagnose the issue, switch some channels around and see which ones flutter?

In my experience, its not the radio but something at the vehicle. Sounds like you are getting some sort of noise due to the engine running.

Does the problem happen at all when the engine isnt running?
Have you recently re-routed the antenna wire or trimmed it?
Is the antenna wire running next to any other wires?
Does the throttle channel glitch as well?

Check all your wires to make sure nothing is frayed/shorted.

Ok, I think I got it.

The glitches occur with or without the engine running, with or without the failsafe connected, and on channels 1 and 2 if I switch the wires on the receiver.

With that said, it's not radio interference, not a faulty failsafe, and not the reciever. It's the servo. It freaks out every time it gets power, and ignores all incoming signals, whether it be from a failsafe or a radio command.

i think that you got the right way to finding the cause.

one comment, before you replace with new servo.
you should check your servo arm about relation of throttle and break setting. and your Transmitter TH EPA setting.
wrong setting can damage servo.

and don't forget about ...
we must don't use analog servo with any High-Response mode.
it can damage servo too.

Transmitter setting, servo response.
Servo Normal mode : use for analog and digital servo
Servo High Response mode : use for digital servo ONLY!

So, you shound know about your FUTABA throttle servo.
it's analog or digital.

It could also be the optidrive if you have that installed still. Really is a POS that craptydrive.

I didn't know a high response mode would damage an analog servo, thanks for the tip. I'll have to check my radio when I get home from work.

The EPA settings are fine, I took my time setting up the trims and EPAs for the truck before I even started it for the first time.

The throttle servo that was giving me trouble was analog.

Optidrive is gone, I took out reverse and installed the center diff.

Why analog servo can't use in high response mode?
it cause of...
analog servo use normal servo standard signal.
the normal servo signal have refresh rate about 14-20 millisecond.
while, the refresh rate of high response mode only 4-6 millisecond.
So, when use analog servo in high response mode, it will have error occur.

Why digital servo can use both normal and high response mode?
it cause of...
digital servo firmware, support both normal and high response signal.

Can the Align DS 620 servo be used for touring cars ? I'm using a Futaba 3PL radio.

I dont think the 3pl has a HRS mode. The3pm-mx has the option to run digital servos in hrs mode.

I think you're right. I don't remember seeing an HRS option while I was scrolling through the settings. I'll look through the manual when I get home from work, but either way, I know the servo bad.