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Discussion Starter #1
I have a 2009 Sportsman 800 H.O EFI that all the sudden started running like junk. The machine is bone stock and only basic oil changes have been done to it.
I have read a million post about the TPS and TBAP sensor harnesses are awful quality, so I started there and tested everything.
I am working on getting a analog meter to test the sweep of the TPS but I have a good quality Fluke with a good sampling rate and it appear smooth (not to mention that it is brand new to the tune of $209)
Dealer set base and idle voltages and I verified them with my meter and everything is in spec.
We did find chaffed but not broken wires for the TBAP while we were on the trail, figured they were shorting out. We had some electrical tape so we isolated them thinking for sure that was it and that didn't fix it.

I metered all of the wires from the connector at the ECM to the connectors at the sensors
Service manual says TPS should be 4-6k ohms across pins 2 and 3 and I think it was at 4.6k if I remember correctly
But I can't find anything on testing the TBAP so I can't really tell if the TBAP is bad or if its the connector.
I will say I have a OTB harness on order even though the wires still conduct fine from the ECM to the connector.
I did also meter the Crank position sensor which is 560 +/- 10% and it was right within spec.

Is it possible that the chaffed through wires fried the TBAP? Does anyone know how to test the actual sensor. I don't really want to throw parts at this thing.
 

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I'd grab a running DC voltage at the battery terminals, @3,000rpm. 13.5-14.5vdc is what it should read. Also a battery voltage, not running should read 12.5+vdc. Once you have established the charging system is putting out optimally an ignition system check should be done, make sure you have strong spark. A fuel pressure check should be done next.

FYI good fuel and tight battery terminals go unlooked and can cause havoc!!! Make sure they're good!!!!
 

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Discussion Starter #3
12.9 sitting still and an even 14 at 3k. I barely made it to that rpm as it would stall as soon as I started it. Battery terms were the first thing we checked.

Is there a service port on the fuel supply like a traditional automotive shcrader valve?
 

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12.9 sitting still and an even 14 at 3k. I barely made it to that rpm as it would stall as soon as I started it. Battery terms were the first thing we checked.

Is there a service port on the fuel supply like a traditional automotive shcrader valve?
Sounds like a fuel pump to me.
Yes, there's a Schrader on the fuel rail.
You need 42 psi.
 

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Discussion Starter #5
I think I figured it out. Guess the plug boots don't really like to be molded around the valve covers too much and the left plug boot popped off the plug. I think it was probably arcing across to the plug making it run kind half way. Makes total sense now because there were times it was very obvious that it was running on one cylinder. Sounded like my 400. Changed out the plugs and made sure the boot was on there good and it fired right up.
 

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Awesome glad you got it!!!
 
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