2014 800 Polaris grief

[ArlyA]

We have the 800 Polaris in our 2014 Boss. This is not the same engine they put in there UTV's for a few years. During the latter half of this winter, it would run perfectly for the first 1/2 and hour or so, then it would start to miss sometimes so badly I thought I might not get back in. No service lights have came on and it does this after it gets warm, every time out. Two area shops have worked on it and cleaned out the fuel tank, replaced fuel filter and spark plus, replaced the ignition coils, checked the fuel pump while cold and warm and it was good. The Y pipe was replaced which is not connected to the missing grief. Different fuel was used from another station and so was premium, which the manufacturer does not call for. NO difference.... Water had not been found in the air intake system either.

Any idea's?

 

[sea2summit]

What are the compression psi(s)?

 

[deezler]

Great story, Arly. Did you have any questions for us?

j/k, j/k.

I am reasonably certain this engine is EFI, right? Did any of the shops try easy things like swapping (if an available spare was on hand) to a different ECU, different air or coolant temp sensors, etc? Yes, you'd think that electronic problems would cause the service light to come on. But sometimes weird things happen.

If it were my machine, I would try troubleshooting things while it is running poorly. Unplug sensors, fiddle with anything you can, etc. Try to find a clue, because your professional repair shops obviously can't.

 

[LittleBill21]

do u get oil in the airbox?

 

[ArlyA]

Not sure if they checked the compression but I will ask them that next time we speak. This is a pretty low hour machine.

If any of its sensors are suspect, the ECU will give an error code. I asked them that very question.

No oil in the air box.

 

[groundcover]

We had a 6X6 499cc that did that , turned out to be a bad cam shaft at 225 hours !

 

[Snobdds]

Sounds like a sensor problem.

Map
Cam shaft sensor
Crank shaft sensor
Engine temp sensor
TPS sensor
Oxygen sensor

Sometimes the range is set pretty wide on a sensor before they throw a CEL. I had this happen on an older ranger. I eventually replaced all the sensors and sold it. There are tests that can be done, but I didn't have the patience to do it.

 

[ArlyA]

Sounds like a sensor problem.

Map
Cam shaft sensor
Crank shaft sensor
Engine temp sensor
TPS sensor
Oxygen sensor

Sometimes the range is set pretty wide on a sensor before they throw a CEL. I had this happen on an older ranger. I eventually replaced all the sensors and sold it. There are tests that can be done, but I didn't have the patience to do it.

My mechanical guys tell me if the ECU says the sensor's are good, they usually are. So they didn't want to replace them willy-nilly. The shops I've used to work on it seem to be straight shooters.

 

[ruffdog]

Being that it is a twin, when it starts acting up, have a spray bottle that mists and mist both header pipes coming out of the engine. If it is only one cylinder that is misfiring, you will see that while misting (cold vs hot). If that is the case, it may be the ignition pick-up coil down by the crankshaft. It is a low voltage coil that sends a signal to the ecu.

 

[Bocephous]

When was the last time valve clearances were checked?