550XP Autotune Issues..

[ajs2654]

Good Morning,
So I was having issues starting my 2014 Husqvarna 550xp. Thinking it was just needing a carb cleaning, I took it to my local dealer. Unfortunately, when they looked at the saw, they alluded that they think it was related to the autotune. I got they idea they were sure how to trouble shoot or fix it. Here is the Work Order Summary:

"Performed Auto Tune but engine will not pass full throttle test.. Tested Compression.. 115 PSI(Needs to be 130-145 PSI Minimum) Checked Cylinder and it doesn't seem overly worn. Suspect Saw overheated."

I don't agree that the saw was overheated. I run a few tanks of fuel through this saw a few times year for an average of an hour use each time. I don't use any ethonal in fuel either.

My questions is where do I go next? Do I sell the saw for parts or is there a specialist out there that might be able to fix it? I am worried that if my dealer can't fix it, than no one can. I have tried asking around locally, but no one can seem to get the password to work on the autotune.

Any help would be much appreciated. Thanks in advance.

Andy

 

[huskihl]

If you have low compression and the piston/cylinder aren't scored, I’d look at replacing the ring.

 

[cuinrearview]

I am worried that if my dealer can't fix it, than no one can.

Sadly, the opposite of this is more common. You do, unfortunately, need a dealer to diagnose an issue with the AT system because they're the only ones with the magic software. What does "performed auto tune" entail? As @huskihl mentioned, a 550 with 115psi isn't going to run very well.

There are many dealers around now who are more in the business of selling new saws than servicing past customers. I'm not saying that this is the case here, but a 2nd opinion from another shop may not be a bad idea.

 

[Vintage Engine Repairs]

Sorry to hear of your troubles. I’be head a lot of good things about Autotune and Mtronic, until they fail. Then it’s a trip to the shops and $ spent on diagnosing and repairs sadly..

It doesn’t sound like they hooked it up to any diagnostic software by what they wrote, so a trip to another shop may be a good idea. However with low compression, but a clean exhaust side piston / rings it’s worth at the very least checking ring end gap and replacing rings if necessary. It’s a cheap and easy job and won’t cause you any troubles.

 

[Fatherwheels]

Good Morning,
So I was having issues starting my 2014 Husqvarna 550xp. Thinking it was just needing a carb cleaning, I took it to my local dealer. Unfortunately, when they looked at the saw, they alluded that they think it was related to the autotune. I got they idea they were sure how to trouble shoot or fix it. Here is the Work Order Summary:

"Performed Auto Tune but engine will not pass full throttle test.. Tested Compression.. 115 PSI(Needs to be 130-145 PSI Minimum) Checked Cylinder and it doesn't seem overly worn. Suspect Saw overheated."

I don't agree that the saw was overheated. I run a few tanks of fuel through this saw a few times year for an average of an hour use each time. I don't use any ethonal in fuel either.

My questions is where do I go next? Do I sell the saw for parts or is there a specialist out there that might be able to fix it? I am worried that if my dealer can't fix it, than no one can. I have tried asking around locally, but no one can seem to get the password to work on the autotune.

Any help would be much appreciated. Thanks in advance.

Andy

I would send it on, if it did the small amount of cutting you say, then it wasn't up to much in the first place.
You paid for a diagnosis, and if you pay for another and are still no further forward, then what, am sure if you
could work on them yourself you would have already done so, that could mean two diagnostic payments,
and a payment for an attempted fix, which may or may not work, given its an Autotune I would sell it as is,
there are people who can fix them, but a lot of them don't work in saw shops, but will buy them because they
know their stuff, then buy a new saw, with a warranty for peace of mind, no Autotune or Mtronic would be my choice,
no need for a computer to tell you whats wrong with them, and just about anyone can fix one, with a bit of coaching
and advise.

 

[cscltd]

When they said it did not pass full throttle test on Autotune diagnostics, that usually means the throttle lever is not going to full open position which could be throttle cable issue or dirt?
they should be able to read any errors codes that unit has stored- but that is the problem with Stihl and husk, they let dealers sell autotune and mtronic saws with little or no direction on how to use diagnostic software or requiring dealers to learn how to use it.

what was your problem with saw, what was it doing or not doing?

 

[Andyshine77]

I i remember correctly if you don't have the correct adapter for the compression gauge you'll get a really low reading. If the compression is only 115psi you'll need to take the top end off and do some investigating. Before you do I recommend having the saw vac/pressure tested. 14 was a really bad year for these saws and a large number of them had defects.

 

[CentaurG2]

I have an early 550xp. That saw has been through hell and back and has never given me one whiff of trouble. Runs like an animal. Autotune can compensate for lean fuel but it won’t save the saw from straight gas. Unfortunately, that saw is close to brake even. If you are not going to be wrenching on it yourself or don’t have the skills/tools, you might be better off purchasing a new saw and selling the gassed saw for parts.

 

[Fatherwheels]

I i remember correctly if you don't have the correct adapter for the compression gauge you'll get a really low reading. If the compression is only 115psi you'll need to take the top end off and do some investigating. Before you do I recommend having the saw vac/pressure tested. 14 was a really bad year for these saws and a large number of them had defects.

That's about the same time a lot of forest workers here went bald, they all had just bought 550XP saws.
Good advise there though.

 

[ajs2654]

Sorry to hear of your troubles. I’be head a lot of good things about Autotune and Mtronic, until they fail. Then it’s a trip to the shops and $ spent on diagnosing and repairs sadly..

It doesn’t sound like they hooked it up to any diagnostic software by what they wrote, so a trip to another shop may be a good idea. However with low compression, but a clean exhaust side piston / rings it’s worth at the very least checking ring end gap and replacing rings if necessary. It’s a cheap and easy job and won’t cause you any troubles.

The next dealer I take it this week, I will mention about the ring ends and gap. Thank you. I am still in disbelief for how nice the saw is, that it just craps out.

 

[ajs2654]

When they said it did not pass full throttle test on Autotune diagnostics, that usually means the throttle lever is not going to full open position which could be throttle cable issue or dirt?
they should be able to read any errors codes that unit has stored- but that is the problem with Stihl and husk, they let dealers sell autotune and mtronic saws with little or no direction on how to use diagnostic software or requiring dealers to learn how to use it.

what was your problem with saw, what was it doing or not doing?

So originally I thought it was a carb issue, because it wouldn't start. It would act like it was going to run and after second it would just die. I took the carb off and cleaned what I could and put it back together. After I put it back together is when I noticed it had less compression in the pull cord, not a significant difference but enough to notice. Could this have affected it?
When I put everything back together, I made sure it was seeded correctly.

 

[Fatherwheels]

So originally I thought it was a carb issue, because it wouldn't start. It would act like it was going to run and after second it would just die. I took the carb off and cleaned what I could and put it back together. After I put it back together is when I noticed it had less compression in the pull cord, not a significant difference but enough to notice. Could this have affected it?
When I put everything back together, I made sure it was seeded correctly.

Taking the carb off would not affect compression. Did you take the muffler off and have a look in to see how the cylinder
and piston look, there should be no scratches or scores or damage. That is where I would start before spending any money
on it elsewhere.
Is there a decomp button, is it sealing correctly.

 

[ajs2654]

Taking the carb off would not affect compression. Did you take the muffler off and have a look in to see how the cylinder
and piston look, there should be no scratches or scores or damage. That is where I would start before spending any money
on it elsewhere.
Is there a decomp button, is it sealing correctly.

I just took the muffler off. The piston looks really good and the cylinder looks like it has light horizontal scratches, no scoring. As far the decomp button, is that the button close to the spark plug? Never really knew what that button was for. How should it work?

 

[huskihl]

I just took the muffler off. The piston looks really good and the cylinder looks like it has light horizontal scratches, no scoring. As far the decomp button, is that the button close to the spark plug? Never really knew what that button was for. How should it work?

See if the button will push in. It should pop out once the saw starts. It might be stuck in, causing the low compression

 

[Fatherwheels]

Not sure what to say about the scratches on the cylinder, is it possible to get a picture of them, horizontal should be ok,
and could just be the machine marks left to help bed in the ring.
As above, check if the button / decomp valve is popping out when you try and start the saw, it should,
would be good if it was stuck in, that would be an easy fix and explain your low compression.

If all is well, put muffler back on, put some two stroke oil into the cylinder through the plug hole, then try and start,
the oil should raise the compression by sealing the ring better against the cylinder wall, if it starts and runs then a new
ring may be all that is required.
Be careful pulling the starter when the oil is in there, it could be a whole lot harder to do and pull the handle out of your hand.

 

[Andyshine77]

Definitely get things checked out, and yes make sure the decmp isn't in when you check compression, keep pulling until the gauge needle stops climbing. That said my guess is the saw has an AT-1A, if everything checks out you'll likely need a new carb, the last carb I know of is the AT-12, that one has worked for me, and no it's not a cheap carb. If the saw does need a new carb or other parts, you may want to cut you're losses and start looking for a new saw, as "IMHO" the 550's of that era are ticking time bombs, other failures will occur prematurely.

 

[Vintage Engine Repairs]

Sounds like the top end is in good condition. I’d expect that the compression tester they used at the workshop to test your saw is accurate, but you can just never tell for sure unless you do it yourself.
WLots of great advice given so far. Pictures would be good!

 

[Fatherwheels]

Definitely get things checked out, and yes make sure the decmp isn't in when you check compression, keep pulling until the gauge needle stops climbing. That said my guess is the saw has an AT-1A, if everything checks out you'll likely need a new carb, the last carb I know of is the AT-12, that one has worked for me, and no it's not a cheap carb. If the saw does need a new carb or other parts, you may want to cut you're losses and start looking for a new saw, as "IMHO" the 550's of that era are ticking time bombs, other failures will occur prematurely.

Sadly true, those early saws could be a real handful to get sorted.

 

[ajs2654]

So I can assure that that piston doesn’t have any scoring on it. The cylinder does have light scratches on it but no scoring. I tried taking pictures of it, but it is very hard with the lighting and getting it focus on. I did try decomp button while trying to start it and does seem to be functioning properly. To me, it still seems like a carb issue. Where is the programming software tied to? The carb?

 

[huskihl]

So I can assure that that piston doesn’t have any scoring on it. The cylinder does have light scratches on it but no scoring. I tried taking pictures of it, but it is very hard with the lighting and getting it focus on. I did try decomp button while trying to start it and does seem to be functioning properly. To me, it still seems like a carb issue. Where is the programming software tied to? The carb?

Software is in the coil, which has to be paired to the carb