High Idle, Dark Plugs

TrailRebel · Jan 21, 2015

Hello all,
I'm having an issue with my 06 Switchy. Since the beginning of the season, I've had my 900 idling at 2200 RPMs when it's cold, 1100 RPMs when it's warm (unless I give it a little bit of throttle, then back to 2200 RPMs). I've inspected all the connections, replaced intake boots, reset TPS (and wiggled the pigtail), replaced spark plugs, replaced gas with fresh, and tested for intake leaks by spraying starting fluid with the engine running.

I found nothing, sled still has erratic idle.

I felt safe enough to ride it, it has good power, but "stumbles" when the throttle is held in the same position anywhere above 6000 RPMs. Increase or decrease throttle, and the problem goes away. Next day I checked plugs...it's running pig rich!!! Started looking over wiring harness, and I couldn't find anything. Took off FnI airbox, started fiddling with the Intake Air Temp Sensor...this is where it gets weird...holding the sensor and trying to heat it up, does nothing. But when blown on, idle drops down to 1600 and sounds healthy. Eventually, the idle will come back up to 2200. When the sensor is disconnected, the idle comes back down to 1600, but flashes a check engine light. I never ohm'd it out, but is there a possibility the sensor is bad? I'd hate to buy a $90 sensor, only to find out it's supposed to do that!!! I also read in the service manual that the sensor resistance should be 9.7 - 10.3 KΩ at 77*...but I've read that some people have problems with the sensor within the stated specifications.

Any help or insight is highly appreciated!!!

Cerialsledder · Jan 21, 2015

if you have already checked everything above then I would start checking PTO crank seal, mag side crank seal, injector seals (o-rings). My switchback was acting like that last year and I ended up having a bad pto crank seal which ended up in me seizing the pto side crank bearings. Not sure if the seal would contribute to that but I'm assuming so

slash · Jan 21, 2015

if your getting a change from the sensor it works but it may not work within the proper range ...works when you blow on it ! but not in place something blocking it's air flow ?

TrailRebel · Jan 22, 2015

Cerialsledder said:
if you have already checked everything above then I would start checking PTO crank seal, mag side crank seal, injector seals (o-rings). My switchback was acting like that last year and I ended up having a bad pto crank seal which ended up in me seizing the pto side crank bearings. Not sure if the seal would contribute to that but I'm assuming so

I checked the seals by running the engine and spraying starting fluid. I couldn't find any spots where the idle would change... The mag and pto seals were replaced early last season, and all of last season there weren't any problems. What gets me, is that the idle is high, yet the plugs definitely indicate rich.

Cerialsledder · Jan 22, 2015

Stuck injectors? Get a bottle of amzoil PI and run it through a tank of gas and see if it helps. If not then I would pull the injectors and have them flow tested and fixed

TrailRebel · Jan 22, 2015

Cerialsledder said:
Stuck injectors? Get a bottle of amzoil PI and run it through a tank of gas and see if it helps. If not then I would pull the injectors and have them flow tested and fixed

I thought about that as well, but both side plugs looked the same...It would just be a weird coincidence for two injectors (or more) on different cylinders to go bad at the same time. It's definitely worth a shot, though!!!

TrailRebel · Feb 7, 2015

So, last weekend, I brought the sled home to my garage so I could do some diagnostics for it. Cleaned throttle bodies, reset TPS from .716 to .710, idle set to .930, replaced the TPS harness up to the ground splice for the coolant temp sensor.

The sled doesn't seem to be as picky about temperature, but now there is no rhyme or reason when it idles up...it's a 50/50 shot whether it idles at 2000 rpm or 1600 rpm. when it's idling high, unplugging any sensor will lower the rpm to 1600 (but flash a corresponding check engine light).

I'm about to go back out and pull the flywheel to check for separation/chaffing.

Any other ideas?

NapaMatt · Feb 7, 2015

You got a case of CHIPPED REEDS!!!

Take the throttle bodys off and the boots and have a look!!

Betting ur missing more then one pedal!!!

whetsel.m · Feb 7, 2015

Let us know what you find out!

TrailRebel · Feb 8, 2015

NapaMatt said:
You got a case of CHIPPED REEDS!!!

Take the throttle bodys off and the boots and have a look!!

Betting ur missing more then one pedal!!!

Reeds were inspected and cleaned when the throttle body boots were installed...everything looked great!

TrailRebel · Feb 8, 2015

whetsel.m said:
Let us know what you find out!

I most definitely will!!!

TrailRebel · Feb 10, 2015

So, I dropped the sled off at the Stealership on Saturday...They finally got around to it today. They found the boots around the throttle bodies on the intake plenum were "bad"...and proceeded to tell me that Digital Wrench cannot read real time data, so diagnostic time is going to be racking up if replacing the boots doesn't fix the problem. He also believes that the FnI intake has something to do with it.

I'm getting the sled back tomorrow and never looking back!!! I'd like to thank them for not listening to a word I say, and proceed to recheck everything I looked over already...at my expense...

I have an appointment on Friday morning for another dealer, whom directed me to "do whatever it takes to get it back" from the dealer it's currently at...his opinion is on the same page as mine, it's likely another sensor out of spec but within range forcing the idle to rise.

So with that being said, what else could I do before Friday morning? Test EGT and knock? Any ideas how?

guidoxpress · Feb 10, 2015

U can ohm most of the sensors easily w/o removing much in the mean time. But I'm not sure if that's the issue, can't put my finger on it either. I would guess tps sensor but it's not a "cheap" attempt to replace and see

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TrailRebel · Dec 20, 2015

Got back around to working on the sled last month. I had injectors cleaned and tested, replaced injector o rings, replaced base gaskets, replaced cylinder head o rings, inspected reeds, replaced intake boots, and inspected all wiring.

Found nothing wrong!!!

I was pretty confident on my TPS setting, but started playing around with moving it (very small adjustments, probably .020" to .030") in each direction...wow, what a difference an extremely minute adjustment makes in engine performance! I had only loosened one screw, and was tapping it in one direction or the other, sometimes feeling like it wasn't moving at all, was making a difference in idle RPM, but made the sled hunt at a lower RPM for idle.

I feel like such small adjustments shouldn't have that large of effect ( 0 - 1000 RPM) at idle. I'm thinking maybe a Throttle Position Sensor? Wouldn't you notice a pickiness in voltage when adjusting it with a tester?

Confusion 900 · Dec 20, 2015

High idle

Have you checked your fuel pressure to make sure the regulator is working ok.

TrailRebel · Dec 21, 2015

That's about the only thing I haven't done this year. I checked it last season when I started having problems, and I don't recall the exact number, but I remember it was good!

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snobrdrydr · Dec 22, 2015

I am having the same thing happen with one of my 900's right now. Pretty much new everything, reset the TPS, and the idle is erratic to the point where you look at the sled wrong and it will change idle. Some times its around 1500, then I ride it, come to a stop and the idle sits at 2800, then slowly drops.

Sometimes if I wiggle the throttle cable it drops the idle down, however the throttle always come back to rest on the idle screw.

Let me know if you find out a fix for yours!

TrailRebel · Dec 22, 2015

snobrdrydr said:
I am having the same thing happen with one of my 900's right now. Pretty much new everything, reset the TPS, and the idle is erratic to the point where you look at the sled wrong and it will change idle. Some times its around 1500, then I ride it, come to a stop and the idle sits at 2800, then slowly drops.

Sometimes if I wiggle the throttle cable it drops the idle down, however the throttle always come back to rest on the idle screw.

Let me know if you find out a fix for yours!

Have you replaced the TPS? I'm thinking when I was tapping mine last weekend, it might be defective.

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snobrdrydr · Dec 22, 2015

I have not replaced the TPS yet. I just reset it and it runs great, no hesitation through any rpm... just an erratic idle.

I have another 900 that runs flawless, I might just swap the whole throttle body/tps from that one to see if that changes anything.

Cerialsledder · Dec 23, 2015

I have a spare TPS in the garage I'd be willing to let go. Test them fully though before you make any conclusions. OHM the TPS out and make sure you see it run through the full range without it jumping. I had an erratic idle when I first bought my switchback 900 and it ended up being a bad stator. Last year the erratic idle came back but was no where near as bad and it ended up being a dirty injector and it leaned it out pretty badly to where I melted the piston :Cry:

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