I am working on a Polaris Sportsman 500 efi it starts every time but as soon as you go to accelerate I lose spark. I have wiggle tested almost every wire harness I can find, replaced the ecu with new, replaced the coil with new, checked cps gap and wiring, disconected the ect and still lose spark under acceleration. What could be causing this? Anything to help would be great! Thank you.

 

Welcome! If you've replaced the control module(by the radiator) and the coil and still have an electrical breakdown, still very like the map sensor or tps sensor harness wires or the wiring may have pulled out slightly from the sensor connectors themselves causing the problem. Also crank sensor wires are bad about shorting out against the starter or engine case. These small sensor wires don't have to have bare spots to be bad. They can have soft spots internally causing problems also.Check the "sticky" post in the expert section about efi wiring problems. Another thing is if you have a fuel pressure gauge and adapter for the fuel rail,the fuel pump should hold 39 psi.If lower or erratic pressure,could be a fuel pump problem. OPT

 

It was the cm by the radiator w/ 2 plug-ins. I have continuity checked the wires coming from the t-bap, tps, cps, and coil. I have a spark tester hooked in between coil wire and spark plug so I can watch the spark. When I start the machine it doesn't miss a beat but as soon as I give it throttle it starts cutting out the spark and dies. If low fuel pressure would it kill the spark?

 

No, low fuel pressure wouldn't kill the spark,but vibration on the small wires from the t bap(map sensor) or tps wiring harness would. This was a common problem on efi models. OPT

 

If I have checked the continuity of the t bap(map) and tps from sensor plug female inside to ecm and have continuity could it still be the harness?

 

Do a diagnostic check and see if any codes show up. Intermittent shorts will not always show up,but if any codes do how up, they possibly can help trace the problem. As far as continuity,yes the harness wires can show good,but if any wire has a partial break internally,wires loose in the connector,then vibration can cause it to act up. Look here on your model under "electrical" and see all the harness kits offered. May not be you problem,but it kept me busy replacing wiring kits on 500,700 and 800 efi machines. http://parts.polarisind.com/Browse/Browse.asp
OPT

 

No codes, the check engine light will flash when it starts to miss but when I run the check all I get is 12 and 62 which I know is start and end. Could this be a cps problem?

 

The ONLY way to tell if the "brain box" is the problem is to have it hooked up to Polaris Digital Wrench software. It can find direct sensor/modules faults,but can't always find an intermittent wiring problem or shorts. OPT

 

Thank you for all the info. I'm going to replace the t-bap harness and try that. My only ther ? was if the crank position sensor could be faulty?

 

Crank sensors can fail,only replaced one or too that I remember(have to have a test harness to check out). Plus also make sure you have 2 mm play between the etc throttle switch contacts. Just pop the throttle control lid and check this out,could be as simple as this? DON'T get the Polaris harness repair kits as they have the same thin wiring as stock . Check the "sticky" post in the expert section for places to get better kits OR check on Ebay for heavier duty kits. OPT