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Discussion Starter · #1 ·
Thanks to the vast amount of expert information from the members of PRC, my 09 6x6 was brought back to life and is now running like a spotted ape except for one issue.

After about 20 minutes of high-end operation (5000+ rpms) it will begin to stutter. Not much at first, just an intermittent miss. But over the next 3-5 minutes those intermittent misses progress to very persistent backfires to the point where the buggy will finally just lay down and quit. When the backfiring starts, the Check Engine Light comes on, and when I check codes I get a "21", which is Loss Synchronization. After about 10-15 minutes of sitting and cool-down, it starts right up and will run like brand new again for another 15-20 minutes then does the same thing.

Also, if I try and start it during the cool-down it acts like the starter isn't engaging. It will make a slight spinning/whirring noise but won't actually turn the engine over. If I keep trying over and over, it will eventually grab, but if I wait the 10-15 minutes it starts like brand new.

Any insight into what may be going on with it would be greatly appreciated.

Lance
 

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Lance, that code usually suggests a CPS issue:

Crank Shaft Position Sensor. CPS:#2410720
The CPS is on the right side of the engine toward the rear of the round stator cover.

It fairly uncommon for a CPS to go bad.
Sometimes you can get away with removing/cleaning the sensor (crude/oil sludge build-up) and/or cleaning the male/female connections and appling a small amount of Di-electric grease, check for frayed/broken wires on the CPS wiring as well.
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Also, I would check the wiring at/around the TBAP and TPS sensors/connectors while I was at it.

*TBAP = Temperature & Barometric Air Pressure Sensor:
The TBAP sensor is located in the air-tube between the throttle body and the air filter. It senses air temp and barometric pressure, and sends a signal to the ECU so that the ECU can adjust the fuel accordingly. Most of the time when there is an issue with the TBAP it is due to broken/bare wires, or occasionally dirt on the TBAP. There is no way to test the TBAP.
FYI - If you clean the TBAP sensor use an carburetor cleaner or an electronics type cleaner, something that WILL NOT leave any residue behind on the sensor.

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*TPS = Throttle Position Sensor:
The TPS is located on the passenger side of the throttle body. It tells the ECU how far open the butterfly in the throttle is. If the TPS goes bad it can make the machine run erratically, or cause a hesitation at certain rpms. The only way to test the TPS is to use the tool Polaris designed to test it, or back-probe the yellow wire at the connector with a multi-meter and watch the voltage as you run up the throttle.
 

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Discussion Starter · #3 ·
Thanks for the info Rich. I've seen several other posts about the CPS but hadn't seen where the description of symptoms was the same as what I'm experiencing.

So I'm guessing the CPS will affects the engine settings based on engine temp and that's why it's acting up at the higher temps?
 

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Discussion Starter · #4 ·
Oh, just fyi, I've recently replaced the TBAP harness and all other issues that you've mentioned, as well as installed a new fuel pump Saturday evening. It runs like a brand new machine until it reaches the higher temps.
 

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Discussion Starter · #5 ·
Just realized another symptom that showed up Sunday as well. My speedo quit working. The digital display still works and will scroll through the different readouts when you push the yellow button, but the needle stays bottomed out and doesn't move. It lights up, but just sits there.

Is that something that may be linked to whatever is causing the spitting, sputtering and backfiring after 15-20 minutes of high end running?

Don't know if it's a coincidence or somehow connected.

Thanks,

Lance
 

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Chris, like was mentioned (in 2012) this is usually a CRANK POSITION SENSOR HARNESS problem. I have also seen a 21 with a TPS that is out of range which is really strange but there are a lot of 'knock off' TPS's that donot work well for sale on EBAY & AMazon . I would suggest you start your own thread and we will get you fixed up .
 
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