Impossible to get rid of interferences in my Baja

[Dashz]

Hey there.
I have been running into this issue for the last 2 months, this is not my first gas car or rc car in general (have had around 3 nitros and 2 gas ones before), so most of the basic troubleshooting has been done already. But this issue is the first time ever.
The car randomly loses signal and then locks into failsafe, ONLY when engine is working and it doesn't LOCK OUT of failsafe until I power cycle the electronics in the car.

Things I have tried:
- Replaced electronics, servos, 3 different types of RX and radio brands ( flysky, Radiolink, even tried a mighty Futaba 7xpr) were installed.
- Replaced spark plug for other one used in a perfectly working 1/5 truck, (NGK cmr7h) also tried other El-cheapo ones.
- Wrapped the ignition coil wire in a metal net and grounded it.
- Replaced ignition coil and wire + plug cap.
- Replaced the tuned pipe for a stock box can exhaust.
- Checked for grounding issues with a multimeter for the rx and servo wires, engine and chasis.
- Disconnected kill switch to discard ignition noise.
- Replaced the 2 servos on the car.

As a side note: This buggy has been working ? for 1.5 years, no serious hits or crashes.

None of that worked and this starts to infuriatingly feel like a curse.
At this point all that is left is to replace the entire engine, pile up another 3 wasted hours + money ;(

Do you guys have any idea? I can’t find anyone else on the internet having this same issue ( and the one I found solved it by changing the spark plug which does nothing for me)
I have a Rovan LT with almost same electronics and engine model, and has never suffered from this.

Update: It seems to happen with more frequency at the moment the engine briefly bogs the last 2 seconds before it dies when running out of gas...

 

[Seandonato73]

what do you mean by fail safe? Your kill switch is going into failsafe mode, or your radio is going I to failsafe mode? And by saying you replaced the coil, you mean with rovan, cy, zen? Have you tried any of these electronics on your other rig or pulled parts off your other rig one by one and swapped them out? Since you have 2 rigs and only one does it, its specific to the rig your having issues with so start swapping parts out, one by one and see what makes it go wonkers.

 

[Rep732]

I don't see a mention anywhere of you having an EMI filter on your killswitch lead from the coil

 

[Dashz]

I don't see a mention anywhere of you having an EMI filter on your killswitch lead from the coil

Thanks, I forgot to add to the list of stuff I tried to “completely remove kill switch from the receiver box and disconnect it “ ?
But thanks for mentioning it as well

what do you mean by fail safe? Your kill switch is going into failsafe mode, or your radio is going I to failsafe mode? And by saying you replaced the coil, you mean with rovan, cy, zen? Have you tried any of these electronics on your other rig or pulled parts off your other rig one by one and swapped them out? Since you have 2 rigs and only one does it, its specific to the rig your having issues with so start swapping parts out, one by one and see what makes it go wonkers.

The buggy loses control for 1 second and then enters in fs mode (brakes applied and kill switch shuts engine off).
I did switch some of the components, the ignition coil for example was from the other rig and was working good in the Rovan. The receivers used for troubleshooting were all 3 new, so thats discarded as well. Throttle servo was replaced for a brand new one.
The only component left to be swapped is the steering servo. (But could a servo cause these issues, even when it works fine ? ... )

 

[Rep732]

How far out is the rig when it goes into failsafe?

 

[Dashz]

How far out is the rig when it goes into failsafe?

It can happen at 1 meter or 100, like I mentioned in op it is completely random, I can “increase the chance” of it happening when the engine is about to die starving.
So more related to rpm range than distance.
(Current radio and rx gives me more than 600 meters of signal lol)

 

[Rep732]

600meters On this rig or when its on another one?

 

[Dashz]

600meters On this rig or when its on another one?

Both this one and my other rig, (also exchanged rx from the Baja to the other one, and the other one worked fine, the baja still faced this issue...)

 

[Rep732]

I recently had a receiver issue luckily mine was warrantied

 

[Dashz]

I recently had a receiver issue luckily mine was warrantied

Yeah, definitely not rx issue in my case, already tried around 4 rxs and 3 different radio brands getting same exact result

 

[Rep732]

Well you have a very unique issue. ?‍

 

[DougStar]

Is the plug cap 100 %
have you made sure there are no bare nicked wires on any of the electronics ?‍

 

[buzzkill]

Do you live near a Nuclear Reactor ??or EMP bomb source ? are you in RUSSIA ?

 

[MonsterAir]

Dare I say, maybe a warn gasket. Like the heavy duty steel reinforced kind?

 

[buzzkill]

Most likely you have a power supply/battery issue , a pulsed loss of power can cause stuff like this , do you have a 2nd car ? if so test the trans/rcvr in it and see if it repeats , if not replace your switches + wires + battery's , you either have a short or an open in the power that is intermittent=.

 

[Dashz]

Is the plug cap 100 %
have you made sure there are no bare nicked wires on any of the electronics ?‍

Wish it was that clear but along the ignition coil I also exchanged the whole wire and plug cap (they work and still work perfectly fine in other car) but issue still occurs in this rig...
About the “bare nicked wires”:

In the entrance for the servo wires into the rx box, there is an ultra small nick in the signal wire of the steering servo, the only servo I haven't replaced....
Tomorrow Im changing that servo.
But out of curiosity, should it matter? In theory high voltage noise is not stopped by a small wall of silicone that is the cable isnt it? The futaba connectors we all use are 3 metal pieces cramping the wires, those should also pick noise all the time no?

 

[MonsterAir]

I've got an RX w/ knick in antenna. Runs fine but does worry me.

 

[buzzkill]

Wish it was that clear but along the ignition coil I also exchanged the whole wire and plug cap (they work and still work perfectly fine in other car) but issue still occurs in this rig...
About the “bare nicked wires”:
View attachment 67381
In the entrance for the servo wires into the rx box, there is an ultra small nick in the signal wire of the steering servo, the only servo I haven't replaced....
Tomorrow Im changing that servo.
But out of curiosity, should it matter? In theory high voltage noise is not stopped by a small wall of silicone that is the cable isnt it? The futaba connectors we all use are 3 metal pieces cramping the wires, those should also pick noise all the time no?

the only real way you will go into failsafe is loss of signal ! power will do that , just a hint , I don't think it is noise.

 

[Dashz]

the only real way you will go into failsafe is loss of signal ! power will do that , just a hint , I don't think it is noise.

Thanks Ill try that tomorrow. Logically I would think that losing power (In the car) would not trigger failsafe state and leave the car locked in fs forever, Im able to switch on and off the car electronics very briefly and very fast, and the behaviour I get is completely different, it stops responding but as soon as power comes back I get control, no failsafe. Also it only happens when the engine idles very low to almost die. Tried placing the car on a washing machine to simulate vibrations LOL. Still no issues with power...

 

[Rep732]

Not sure if you mentioned but are you using the same transmitter with all of the recievers? I know for a failsafe it usually starts on the transmitter side because if you had an issue with the car or loss of battery failsafe wouldn't kick in