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Discussion Starter #1
I have a 1997 EXT EFI 580, and I think the Throttle positions sensor is bad.  I have absolutely no dealers around me who know how to do a test like this.  I would love to find one for myself.  Anyone have any Ideas?
 

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What is your sled doing?  A good ohm meter and a manual will work.  There should be an LED light that tells the codes too, or point you in the right direction anyways.
 

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Discussion Starter #3
The sled only has 500 miles on it, and the problem is intermittent.  I have ohmed out all the wires, sensors that could be, and have replaced CDI,and ECU.  The problem is that the motor will not maintain 8000rpm or above when throttle is depressed completely.  It will maintain 8500(up on stand) with the throttle 1/2 to 3/4 open, but as soon as you put it wide open it falls off into limp mode.  The only thing I can come up with is a TPS(throttle position sensor). It ohms out perfect but I need to get an angle and voltage reading out of it.  And there are no dealers that want to work with it, can you believe that.  I want one so I can trouble-shoot for other people, for penies on the dollar and screw all the dealers!  I will just have to advertise.  What do you think?   OH and it has nothing to do with ignition, such as coil or stator.
 

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First, are you sure your clutches are fine.

Second, if you are going into limp mode you should be able to get a code from your computer.  The red light will flash a code if a sensor is not working properly.  A repair manual can tell what the codes mean.

Third, you can do a dc voltage test on the TPS on your own.  You need the specs from the manual.  Then take a couple of pins (like sewing pins) and backprobe (put the pins into the back of the tps hookup coupling where the wires come out of the coupling.  Simply push the wires into the foamy material around the wires and push them all the way in.  You may have to try this more than once so that the pin makes connection with the metal termianl) the TPS sensor.  Hook your voltmeter to the pins, turn your sled to on, not run, and you will get your dc voltage readings at idle and full throttle.  I would be surprised if you do find a problem if the ohms checked out.  If you need more help let me know.  Also note I did this with a first generation efi, but it should be similar.
 

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Discussion Starter #5
Thank you pro-vet for your help.  Yes I have a manual, and what a coincidence, I even used the safety pins.  I did get the voltage and it was perfect to the book.  The brain box flashes once and has no faults.  all the sensors are ohming out perfect.  I have no idea other than a broken wire.  So I re-ohmed all the wires again, it is the third time!  I can not find the fault. It is however electronic though, because 1 time out of 10 the sleds works, and when it does it runs great until I railer it or let it sit for a while then it goes into a broken mode!  Wiggling the wires does not make it change either.  This is a really tough problem, WOW!
 

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Could be a fuel problem?  I've seen fuel pumps do weird things, it doesn't set a code either.  On the stand it don't need much fuel, but when you put a load on it, it has to have the right pressure. (or too much pressure)  I'd rig up a fuel pressure gauge and check it out.  check the return line for a pinch.
 

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Discussion Starter #7
Thanks and I willl take your advice, Sunday I will do the fuel pressure test on this rail.  It was checked at a dealer but only at idle(36.2) perfect!  I need to check it at high revs.  Just to let you guys know, the plugs are wetand black, I can run it up on a stand at 3/4 throttle at 8400rpms for 1 minute and then put the throttle lever down passed 3/4 and it goes back instantly to 6500 rpms and won't move up at all.  to get it to go back up you have to take it to idle and throttle it back up to 3/4 (8400rpm), as long as you stay at 3/4 the motor will turn 8400rpms(up in the air).  But when you go any further it bleeds back down to 6500 or so.  And you remove the plugs they are wet black, so it is not a lean condition I have !
 

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Artic 580. My 2nd sled is a 97 zr580 efi. I had a problem last year with it that it was running to rich and would not even pull it self when engine was up to operating temp. It was ok when engine was cold. But after about 3 minutes of running you would have to keep pumping the throttle to get it up to speed. Hard starting also when engine was warm.would keep flooding. I found that the water temp sendor under the thermostat hgs. Yellow wire. had failed and there was a open curcit at that sender. This would put the ecm into rich mode and it would hardly run.
Just a thought.
TAZ800.
 

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I had a 98 ext efi dux had the same trouble messed with it for a week finally called Cat there was a service update on the 98 to add a second and heavier ground wire to the brain I would bet it is the same deal.
 

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Yup, can't hurt to add another ground wire.  I added another ground from my pull start housing to bare metal just to make sure it is always grounded.  Adding a wire to the brain is even better yet.
 

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arctic580,

Have you tried to run the sled with the Throttle Saftey bypass plug installed?

I had a simmaler problem with my 580EFI (same year).  The throttle saftey switch in the throttle block would cause problems on mine.  

I also had a problem maintaing a good ground to the ECU.  to correct this issue I used some star washers on all of the gound wires mounting points as well as the mounting points of the ECU to the mounting plate.

6Mile
 
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