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Discussion Starter #1 (Edited)
Hi There. I have a 2007 sportsman 800 that has trouble idling and revving up. Once I give it throttle slowly it will rev up and run good at high rpms. If i apply the throttle quickly it will just backfire and die.

I put new plugs and wires on it. Replaced the TBAP sensor harness (saw a bare wire). The previous owner replace the injectors/wires (probably didnt need to). I trace every wire back to the ecu and tested it with my ohm meter for continuity and all check out ok (tbap and tps). I also checked the crank sensor for bare wires and all ok.

The codes I get are 41 45 51 and 52. I am at a loss I checked for wiring problems around the ecu and fuse block, swapped relays, visually checked the spark all okay. Sprayed carb cleaner around the intake and throttle body checking for leaks, okay. I cleaned the TBAP sensor itself with contact cleaner. Fuel pressure is right at 39 PSI. I hooked up a test light to the injector wires just to make sure they are pulsing on/off and are okay. Plugs are black and exhaust is rich

I am now at a loss. Could it be the ECU or coil packs?

Let me know any help is appreciated!
 

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From the service manual:

The Polaris ATV Instrument Cluster is powered by battery
voltage (12 VDC) and requires inputs from the engine RPM,
transmission gear, and speed sensor for proper operation. Two
harnesses plug into the cluster head; one from the speed sensor,
and one from the vehicle main harness. A non-serviceable
internal memory battery maintains odometer and hour meter
data when the machine is not running. The illumination lamp
inside the gauge is non-serviceable and is designed to last for the
life of the unit. (A) The speedometer needle indicates speed
from an electronic speed sensor. The needle also flashes during
a warning condition. The speedometer needle indicates speed in
MPH and KPH. NOTE: A flashing needle could indicate a hot
engine, low battery warning, or the No. 10 Pin could be
grounded. (B) The speedometer face features numbers in Mile
Per Hour (MPH) and Kilometers Per Hour (KPH). (C) The
Rider Information Center performs a number of functions
 

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From the codes it looks like wiring.
Have you tried unplugging the T-BAP to see what it does?
Your description sorta sounds like how a TPS with a dead spot will act but try unplugging the T-BAP first.
Other than that I'd say bad wiring.
See if you can clear the old codes too.
 

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Discussion Starter #4
I tried unplugging the TBAP and it makes no difference. But I did check the wires from the sensor back back to the ecu for continuity and theyre ok. I also checked to see if there were bare spots touching the frame or something and nothing. So either the ecu is bad or the sensor itself is bad. I dont know how either could go bad both are sealed units.

I also checked the TPS and there is a difference with it unplugged and also I took i right off to manually turn it to check and it does make a difference (yes I know Ill have to adjust later on).

All that said Im starting to believe its the coil. Every other piece of equipment Ive worked on has the same symptoms as this atv, which ended up being the coil, spark plugs or wires. Since I replaced the plugs and wires it could now be the coil? The hard starting condition I forgot to mention could be due to weak spark. When I check the spark visually the first spark is very bright and intense and the next sparks are less intense but still blue.
 
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