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2008 Yamaha rhino 700 won't idle ((help )

18K views 28 replies 3 participants last post by  Heywire77 
#1 ·
I'm having hell with my rhino it is 700 fuel injected , I completely rebuilt the engine new crankshaft, piston ,valves , and water pump gears and chain , new spark plug , oil and filter and headgasket set ! Now my problem when I crank it up it will idle for just a second and the it won't idle on its on I have to keep my foot on the pedal or it will die , so I adjusted the throttle plate , and tips according to factory spec and still same problem and idle air valve sensor gets really hot , so I purchased one off a running machine and still same thing so I purchased another just to make sure but same thing , also replaced the intake air pressure sensor but no help , at first the dash was displaying code 37 but when I replaced iac sensor it went out but still want idle on its on , I've been a mechanic for over 20 years are master certified so I know alittle bit about repairs but this dam rhino the book doesn't tell you enough to actually be able to check certain things , I have good compression and my valves are adjusted right and machine has plenty of power going down road but the idle problem is crazy , I'm wondering if I have a computer problem because everything in the throttle body has been replaced and it is clean and all ? I notice the idle valve is getting really hot when I take it out it is fully open , if I crank it with it still plugged in but take out the throttle body machine will idle up and the valve I can watch it move out , if I had to say I would think with it in the throttle body that the computer is telling it to open constantly so that's why it is getting hot , also the manual says the intake air pressure sensor is suppose to have certain reading on volt meter but it is ready below what the book calls for that is why I replaced it but the new one reads the same thing any help I would be thankful .
 
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#4 ·
You said you adjusted the throttle plate, but did you check the throttle position sensor? You can check it's range using your dash computer. If it is within specification, try adjusting to the higher side a little at a time.
 
#5 ·
Yes I did all that I started at 15 and tried it all the way to 20 and still no help , I don't think it is right with the iac sensor getting really hot either . I checked and cleaned air filter made sure it was no blockage Anywere going to throttle body and all .
 
#6 ·
When I worked at dealership years ago before I went in to business for myself al I did was driveability , I wasn't a parts replacer . I don't like throwing parts at it till its fixed I have took all the reading from the sensors on the throttle body that the manual calls for and there all within spec . Only thing I haven't checked yet is fuel pressure but I would think that would cause it to run like crap always . I have checked the spray pattern of the fuel injector and it is good and there isn't any leaking fuel like a stuck open injector or anything . I pulled all the wiring out the fuse box under hood and went thru all of it changed relays out , and went thru all the wiring at the throttle body to make sure not open Anywere .
 
#7 ·
It's not the fuel pressure. There was a user with similar issues and it turned out to be the spark plug which is weird. Something wrong with the idle circuit. I know if I ever get my efi setup on my rhino, the first thing I'm going to do is bypass the iac sensor.
 
#8 ·
Yeah I know for sure it's not the spark plug , at first when I went to replace spark plug after redoing motor they only had one that was one heat range colder said to use till the other one come in I did it and it was idling bad then I got the right spark plug bran new and still same problem . What I'm guessing is that the computer gets the reading from the intake air pressure sensor and then tells the iac to open or close according to pressure and I put a brand new intake air pressure sensor in it , I'm thinking it has to be the computer not working right .
 
#10 ·
No how the iac works is that there is a hole in the filter side of the throttle body that feeds air to the iac valve then when it opens it goes thru to the intake side of the throttle body allowing more air without the butter flys actually opening . I heard one person say on another site that they filled the holes with silicone , I'm about to the point of trying that .
 
#12 ·
Yeah I understand that , I restore boats for a living now and I have built a lot of carbs on inboards and outboards and adjusted the mixture screw , I just got in from trying to mess with it some more I did pull out the iac valve and plug the holes temporary and I actually got the idle to adjust were I don't have to keep my foot on it and can get it to go in gear without it grinding from being idled up so high , I drove it down the road and it ran fine came back and it idled fine still and then I checked made sure the tps was still in specs and I noticed it had 3 code a 13 , 15 , 37 and a couple more . I also remember before I done all this and got the new iac valve put in it had a **** load of codes about 5 of them and every sensor checked out fine , I would about bet that the computer is causing all the problems if I had someone close I would borrow one to see because I hate throwing away a couple hundred dollars if that isn't it . And if it was totally possible I would just about find a carb and put on this thing , it would be better then this junk they call fuel injection !
 
#13 ·
I know when I install mine, I'm going to bypass as many of those sensors as I can. Then I'm going to piggy back a powercommander and let it control the efi. I do this now with both Mukuni and Keihin systems at work.
 
#15 ·
Ok I may have figured something else out I was going thru the dash diagnostic and when I try to do the one for code 37 for the iac valve it is suppose to actuate the valve and it doesn't do anything except the fuel pump starts running and that isn't right there is a few didn't numbers I can go thru like to see all the codes and the fuel pump will come on with them also , there is one code check and that is the only one that is suppose to start the fuel pump so I don't understand why when I'm checking all the other code checks the computer is turning on the fuel pump ? I think something is screwed up in this computer , also I know this rhino once under water at one time by the previous owner he had it snorkeled above the roof and inside the battery box were all the fuses are was soaked and full of mud there was some mud in the throttle body also when I got it , he just kelt running it till he blew it up . I have went thru all the wiring and fixed a couple wires and cleaned every terminal and plug up inside the ecu / computer plugs was mud and I cleaned all it up , I removed all the snorkels and put everything back factory , when I got it the bottom of the piston skirt was busted out , he has removed the thermostat and hot wired the fan and kept running it and the main problem was the water pump and oil pump runs on a chain and gears inside the motor and the chain and gears were worn out chain wouldn't stay on gears so it wasn't pumping oil or water ! I fixed everything , I have even replaced all the axles he had 3 that was busted . I can't stand it when people rig stuff up !
 
#19 ·
I siliconed the isc air bypass closed and used the butterfly stop screw to set idle speed.
I ran mine with no isc plugged in for quite some time. Also whenever changes are made to the throttle stop i always reset tps to .68, i set idle speed and tps at the same time as they effect eachother. You really dont need the isc at all.
 
#21 ·
I fixed it ! I can't believe it I tore the throttle body all down and checked for slack in the throttle plate and took out all the silicone out of the iac valve passage because it didn't help ! I then started over pulled spark plug checked gap , checked timing to make sure it hadn't jump timing and check the valve adjustment and noticed the exhaust valves were tight , so I adjusted the exhaust valves and set my tps back to 17 and started with the idle adjustment screw not even touching the throttle adjuster , hit the key and it fired right off and idled just like it was meant to I didn't even have to use the idle up screw !
 
#23 ·
I had done pulled everything back apart the air boxes and wiring harness , all I can think is the exhaust valves were staying open causing it not to idle , as soon as I fired it up I could tell the difference in the smooth idle , I shifted it in gear and it never sputtered or anything I will see tomorrow for sure but it has never even started to idle on its own without adjusting the idle screw up high . I will taken it down the road tomorrow and see if it still idles good and all but i must have not adjusted the exhaust valves right before I installed the head . I just had to go back to the first and recheck everything . I did pull the throttle body all the way down and checked every thing all the seals and all . So tomorrow I will know for sure because when I did the silicone to the iac valve port at first I adjusted the idle and road it that night and the next day back to a ****ty idle .
 
#26 ·
I have another question for you I have been running the rhino and the other day my fuel pump went out so I bought another fuel pump and I can tell the difference in power now but my question is if I punch the throttle to the floor I can hear it climb really high rpms and it will cut out alittle is that normal or are you suppose to be able to hold them to the floor starting off and the throttle never cut out , it isn't like it is boggin or anything it is like it is really high rpms and the top speed with my 27x11x14 tires is 38 to 39 mph it will cut out if I try and give it more throttle . May just be me I have had atv and you can stomp them to the floor and they will never cut out no matter how high the rpms when it does this some it is starting out I can give it full throttle and I can get up to about 20 real quick but then if I don't let off the throttle alittle it will cut out on me ?
 
#27 ·
You have a rev limiter in the ECU that kills the rpm at I think around 6900.
Do you know what CVT mods were done by the previous owner? Have you had the CVT apart? Sounds like maybe he had some light weights to generate a lot of low speed wheel spin for mudding. Is that top speed in Low or High?
 
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