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MTronic diagnostics / ecm failure symptoms

ABarrick

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I’m looking for a little help with determining what’s going on with my 462. The saw runs and cuts “ok”, but has become sluggish off idle. No longer has the lightning quick throttle response and acceleration it once did. I don’t have any repair manuals for anything m-tronic to see what stihl shows for a correct diagnostic path.

I’ve done the recalibration several times since the weather has been anywhere from 40-80* in the same two day period here lately.

Timing is (was) advanced about 6-7* and muffler modded. Roughly .700” diameter hole in stock location. I put the timing back to stock to see if it had any affect on the situation. No change.

Changed plug, no change. Color indicated a good tune.

Pulled carb, no dirt found in screen, everything looked fine. Fuel line is not restricted.

Fuel is same batch that runs fine in other saws.

I’ve exhausted all the simple stuff, so now I’m down to blaming the coil/ecm or the carb solenoid. Has anybody had a coil fail that still ran but was doggy?

The saw has about 12 or so tanks on it. It ran good stock, ran really good after the muffin mod and timing adv (about 3 tanks that way) and now it’s just irritating me.

Thanks guys.

AJ
 

ABarrick

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I’ll grab a solenoid next time I’m at the dealer and try that I guess. I had always heard they acted rich when solenoids fail and it doesn’t seem rich.
 

ABarrick

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How’d Aj, How’s the new little fella doing?

I just had a 201 doing the same thing and a solenoid fixed it. Good luck and keep us posted.
Good to know about the 201. Little guy is growing like a weed. Been struggling with some stomach/digestive issues but overall he’s healthy and usually happy.
 

PogoInTheWoods

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Whatever. I'd at least throw some fresh mix at it before chasing ECM ghosts and jumping through all those other hoops.

Sure would be embarrassing to take it to the dealer for a new solenoid or ECM diagnosis (which basically doesn't exist anyway) just to find it didn't like the particular batch of fuel in the tank..., or worse...the mix oil!
 

ABarrick

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Try a fresh batch of fuel. A 462 M-tronic isn't 'other saws'.
Fuel is fresh VP sef mixed with ultra (yes, the most horrible oil ever :eek:) at 40:1. “Other saws” include a 462 standard carb, a 261c, a 661 carbed, a 261 carbed, a 461 and a 440, so I ruled out fuel. This 462 ran fine on the same batch of fuel for several tanks before it took a fit.
 
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