Devinlowe18
RCTalk Basher
So I bought a nitro 4-tec 3.3 from a guy off craiglist (yea I know what your thinking already...UGH... Lol). So I immediately swapped the pull start with the the EZ start. It took forever to get the engine started but finally did. It seemed to start running fine but was running really rich. I made two or three passes and it didn't do the kind of speed I'm used to seeing from a 4-tec I would estimate about 40 -45mph. It went dead on me a once again took forever to start again. I also noticed when you touch a pair if pliers to the cooling head ALL the servos would "jitter" not enough to give it throttle or turn the steering but I little "jitter" whenever the metal touched the metal. Anyway moving on. I Finnally get this things started again and take it down the street at about half throttle. On my second pass I have it at about half throttle when the thing spiratically went full, then no throttle for a SPLIT Second, then full throttle until it flipped into the grass and died. I was trying to steer while this was goin on buy it was going to fast to respond. When I picked it up the steering and throttle servos were still responsive to my transmitter. I looked it over and nothing was broken that I could see. I walk the long walk back up the street to the house and try and turn the engine ove but it appears to be frozen. I take out the glow plug to find the piston is SHOT! Now the question is did this happen as a result if the throttle servo maybe malfunctioning and holding it wide open( although it was only a total of like 5 or 6 seconds) or did it all happen because te engine was going bad until the piston popped? Has anyone else ever seen this? And the bigger question. Now I have an excuse to buy a new engine what should I get. I could always put the 3.3 from my tmaxx in the 4-tec and drop something better in the tmaxx. I don't want to have to change alot of parts or put too much stress in other parts though. Also would want it to drop right in.
*UPDATE*
I figured out the problem.
Started by turning on radio and receiver and checking the responsive ability of the steering\throttle. Everything checked 4.0 for about five minutes. During this time I was tapping on random places(servos, receiver, radio, etc.). Finally after some time I got the jittering servos back in both servos then it went away again, then BAM out of nowhere it went WOT and stuck and the steering was jittering. So at this point I swapped crystals and the radio with some from an old 2.5 Maxx of mine. It took some time but eventually I duplicated it again. Out of nowhere WOT and jittering steering servo. So I then determined it was a bad receiver. Swapped receivers and everything ran smooth...
I'm glad I found the problem but it sucks I had to ruin a perfectly good motor to do it. THANKS for all the help.
*UPDATE*
I figured out the problem.
Started by turning on radio and receiver and checking the responsive ability of the steering\throttle. Everything checked 4.0 for about five minutes. During this time I was tapping on random places(servos, receiver, radio, etc.). Finally after some time I got the jittering servos back in both servos then it went away again, then BAM out of nowhere it went WOT and stuck and the steering was jittering. So at this point I swapped crystals and the radio with some from an old 2.5 Maxx of mine. It took some time but eventually I duplicated it again. Out of nowhere WOT and jittering steering servo. So I then determined it was a bad receiver. Swapped receivers and everything ran smooth...
I'm glad I found the problem but it sucks I had to ruin a perfectly good motor to do it. THANKS for all the help.
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