WTF is wrong with my idle?

[yz400ex]

I finally got a chance to take this 900 out today.. did great.. ran awesome.. Only problem was with the idle.. I set the TPS to specs before taking it out.. it started, ran and idled just fine.. got up to the hill.. started it up, it sat and idled just fine.. got up to temp and we took off.. idle was sitting at 1450 at home and before we rode out on the hill..after riding for awhile the sled had an erratic idle.. when you first stop, idle was at 2200-2500, then (only sometimes) after a few seconds would drop down to 1500-1600.. This is while the sled was running at 122-130 degrees.. Then when you would stop, turn the sled off and let it cool down while eating lunch or something, the sled didnt want to idle at all until it got back to around 120 degrees.. It would try and idle so low the gauges wouldnt even turn on.. Just like the TPS was off again.. Not sure what is causing this.. No check engine lights or anything like that..am going to check the stupid TPS again, but anyone know of anything else that may cause this and how to fix it?

 

[frozen north]

do you have a riser?
Do you have the driver select delete?
If you have a riser-how big is it?
Do you have a extended cable?

 

[yz400ex]

I guess I should have mentioned this stuff.. 4 inch riser.. No rider select delete. throttle cable is not being pulled at all.. It is plenty long for this application.

 

[guidoxpress]

did you check the TPS with an analog voltmeter?

you might have a dead spot in the TPS itself..

did you update the TPS harness or check the wiring for any bad connections?

 

[yz400ex]

I didnt check it with an analog meter.. Just a digital.. Did not update the harness, but did check for bad connection when I was originally setting the TPS and it was all good.. Maybe I checked the wiring wrong.. what should I do to check and make sure its good to go??

 

[dmaxd2500]

I just went ahead and replaced the harness connector even though it checked out ok. Then I wired the old connector to my tps tester. Sounds like some sort of tps prob to me. How does your reverse work?

 

[yz400ex]

It worked at home, but not up there at all..would just die..

 

[dmaxd2500]

I would bet you have a connector problem. It's cheap and easy to do, I would just change it and see what happens.

 

[yz400ex]

It might be.. How would you suggest I check it to be sure??

 

[dmaxd2500]

Take a meter and test the continuity of each wire from the tps connector to the ECU connector where it plugs into the ECU. You will probably need a wiring diagram so you can determine the correct pins to check at the ECU connector. Or even before you do that, start the sled up and wiggle the wires and connector at the tps and see if that changes how it runs. This isn't a foolproof test but it might give you an idea if you have a problem before you do the continuity tests.

 

[guidoxpress]

Take a meter and test the continuity of each wire from the tps connector to the ECU connector where it plugs into the ECU. You will probably need a wiring diagram so you can determine the correct pins to check at the ECU connector. Or even before you do that, start the sled up and wiggle the wires and connector at the tps and see if that changes how it runs. This isn't a foolproof test but it might give you an idea if you have a problem before you do the continuity tests.

bingo...try this first..

 

[yz400ex]

Thanks for all the info.. I will try all of this tomorrow if I get a chance and post back my findings..

 

[yz400ex]

Also wondering if this could be my exhaust sensor?? Can a bad one cause problems like this?? Like I said, no check engine light.. Just wondering..

 

[sleddude]

I just went ahead and replaced the harness connector even though it checked out ok. Then I wired the old connector to my tps tester. Sounds like some sort of tps prob to me. How does your reverse work?

Bad TPS harness would be my guess also.

 

[sw]

Also look to see if tiny spring between throttle sync. tab is still there and properly seated.

 

[yz400ex]

Spring is there and fine.. started right up and idles fine right now.. I checked the TPS again before I started it and it was still dead on.. started it up and let it idle.. sat between 1500 and 1600 the whole time.. I wiggled the wires at the TPS and the first time I did it, it died.. This was right after it started and it sometimes does that anyway so not sure if it was me doing that or it just died, but I tried moving them around a lot and it never changed anything or died again.. I never got a chance to check them at the ECM plug yet since I have to remove the tank again to get to it.. How do I remove the wires from the plug? I have a spare harness here and found the wires in the plug, but cannot figure out how they come out.. Any ideas?


What does this sound like now that it will idle again?

 

[AKSNOWRIDER]

Spring is there and fine.. started right up and idles fine right now.. I checked the TPS again before I started it and it was still dead on.. started it up and let it idle.. sat between 1500 and 1600 the whole time.. I wiggled the wires at the TPS and the first time I did it, it died.. This was right after it started and it sometimes does that anyway so not sure if it was me doing that or it just died, but I tried moving them around a lot and it never changed anything or died again.. I never got a chance to check them at the ECM plug yet since I have to remove the tank again to get to it.. How do I remove the wires from the plug? I have a spare harness here and found the wires in the plug, but cannot figure out how they come out.. Any ideas?


What does this sound like now that it will idle again?

they make a special tool to release the wires..normally if you are carefull you can do it with a small buggerpicker..

 

[dmaxd2500]

How do I remove the wires from the plug? I have a spare harness here and found the wires in the plug, but cannot figure out how they come out.. Any ideas?QUOTE]

You don't have to remove the wires from the connector. Just unplug the tps and ECU connectors and use your meter leads to touch the terminal inside the connector. Check the resistance in each of the 3 tps wires, you shouldn't have more than about 1 ohm resistance if the wire is good. Also try wiggling the wires at the connector while you have the meter hooked up to see if the resistance value changes. You can use a T-pin or a small paper clip to stick in the connector terminals if you have alligator clips on your meter.

 

[yz400ex]

I know I dont have to remove the wires from the plug to test it, but if I am going to replace The TPS harness I will need to remove the pins from the plugs.. I just have a spare wiring harness here so I am testing on it before I go into the one on the sled.

 

[yz400ex]

they make a special tool to release the wires..normally if you are carefull you can do it with a small buggerpicker..

Have any idea what this tool is called?? I tried getting them out and cannot figure out how they release..