PRC Polaris Ranger Club banner

1 - 14 of 14 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter #1
Hey PRC Members,

New to forum but have been using it to find solutions for years. Thanx in advance for any help or replies!
So as title states the rzr runs great till warms up then loses power and sounds like popping back thru throttle body.
This happens within 3 or 4min of starting bike unless has been ran then does sooner
I will list things ive looked at and noticed

1. compression 150pis on each cylinder
2. fuel pressure 40psi however i changed pump anyway with ebay one - no difference
3. changed plugs, wires, coils
4. new fuel, vent clear
5. tried new reg/rect from caltric - no diff
6. cleaned t-bap, throttle body
7. inspected wiring at t-bap, tps, cps
8. set tps to manual spec at .735 but ran rpms up way too high so set back to .680 for 1200rpms
(this was performed by piercing yellow wire with my fluke)
9. ohm'd out cps - ok, injectors - ok


one plug is little rich and other may be little lean
charging voltage is good till fan kicks on then drops as low as 12.6 or so - this is a concern but problem starts before voltage drops and continues when fan kicks off and voltage returns to 14.1v

if disconnect one plug wire it has more drastic effect than the other. used inline spark tester and both fire
if disconnect one injector it has more effect than the other

excuse my forum etiquette if off im fairly new to forums
any input or suggestions would help thanx Mike
 

·
Registered
Joined
·
6 Posts
Discussion Starter #3
with compression test looking ok on both cylinders, yall think i can rule out mechanical and focus on electrical problem? possibly t-bap sensor or ecu??
 

·
Administrator
Joined
·
6,360 Posts
Welcome to PRC! Good write up. Trying to remember what I did to my 800 when it was backfiring but that was a few of years ago and I'm really old (I check my drivers licence every morning to see who I am!). Anyway, I believe that my problem turned out to be one of the sensor wires (TPS? - I replaced several at that time). Although the wires looked OK there was one that broken inside the insulation (a common problem back then). Hard to find, gotta look and feel pretty close for a thin or spongy spot in the wire. I'm no engine guy so hopefully one our engine gurus will chime in.
 

·
Registered
Joined
·
2,673 Posts
It's a long shot, but an intake valve could be sticking after the engine warms. Can be caused by fuel/carbon deposits, weak valve spring, bent valve stem or severely worn guide. If you eliminate that possibility I'd be thinking like Forde and look for some electrical issue.
 

·
Registered
Joined
·
387 Posts
One thing you haven't looked at and cleaned is your spark arrester. It's at the back end of your muffler (assuming stock muffler) After years of use they can become clogged and in need of cleaning. There is a screw (bolt) on your muffler outlet, take it out, then you should be able to get the spark arrester out. Clean it and reinstall (Federal law requires it to be installed). Dirty arresters will sometimes cause performance problems - worth looking at.

Mike
 

·
Registered
Joined
·
6 Posts
Discussion Starter #7
Thanks guys, i will look into those. MikeT may be on to something. i replaced the gasket were pipe meets the muffler. i cant recall if this problem was there before i fixed gasket leak.

Pyro, how would i check for sticky valve? Just look under valve cover for signs or have to pull head?

sensor wires appeared good but will check closer

let yall know how goes
 

·
Registered
Joined
·
5,300 Posts
m, I am thinking your TPS may be shot because your 'set' and spec is off a mile. Take the cover off the side of the throttle body so you can access the linkage, then set up your FLUKE like you were setting the voltage on the sensor. Then............slowly open the throttle and watch for jumps (forward and backwards). You should hit wide open throttle around 3.7ish volts. If the TPS does not advance smoothly and hit at least 3.6, the TPS is shot. If that TBAP harness has not been changed (check for splices about 6" from the sensor, it is bad... https://otbpowersports.com/product/t-bap-wiring-repair-harness/
 

·
Registered
Joined
·
2,673 Posts
Before I went into engine disassembly to check for a sticking valve I'd be absolutely certain that the cause isn't elsewhere in either the fuel or ignition system. Forde, Mike and Kris have given you good leads. Be sure to look into those areas first.

If you've exhausted the other possibilities with no remedy, if it were my engine, my next step would be to try something like Seafoam in my engine oil and fuel, as prescribed on the container's instructions. These "snake oil" remedies do have some value and they can break up carbon deposits and sticky residues if they have time to work and can get to the trouble area. If that didn't resolve the issue after driving a few days the sticking valve may be worth investigating further.

You might be able to peer into the intake port and see if there are heavy deposits on the valve stem by removing the manifold and peering into the port with a flashlight. You could inspect the valve spring for a break by pulling the valve cover. Your conclusions will still leave questions if you stop there without finding definite evidence of trouble.

With a little more effort you could put the piston(s) at TDC (top dead center) with the plug removed, push a small diameter rope into the combustion chamber so the valve cannot fall into the cylinder, remove the valve cover, remove the rocker arms, compress the valve spring enough to remove the keepers and remove the spring retainer and spring from the valve stem. At this point you can pull the valve spring and have it checked. You need to check length and squareness to be certain the spring isn't bent, then pressure at installed height (valve closed) and valve open length. You can also check the valve guide for wear by checking side to side movement and then CAREFULLY slide the valve open and closed feeling the amount of resistance required and for any tight places throughout the range of travel. You will probably have to at least partially remove some of the previously placed rope to give the valve room to move up and down but use extreme caution so as not to drop the valve. If you do, you are in for removal of the head. If you feel a tight place as you move the valve through it's range of travel you will likely have to remove the head for further inspection and remedy. Tight places could be caused by deposits built up on the valve stem or a bent or badly worn valve stem.

I cannot stress enough how important it is to exhaust all other possibilities before going to this trouble. If you don't you may end up doing a lot of work with no tangible reward.
 

·
Registered
Joined
·
387 Posts
The 08 model had a design flaw with the intake, The symptoms you describe do not match the catastrophic failures the bad design caused however. The design of the original intake track used a non-pleated intake tube that allowed dust and dirt to enter the engine while riding, this obviously caused many an 08 engine to end up on the rebuild bench or the scrap heap. I didn't mention this before because your compression readings are both within spec. Polaris changed the design for the 09 model year and offered modified intakes to 08 owners that had not upgraded to aftermarket intakes. You have probably already inspected you intake to be certain there is no dust or dirt in the track, if not it would probably be worth it to take a look to be certain it's clean.

Mike
 

·
Registered
Joined
·
2,673 Posts
Thinking about this a little more the thought came to me that perhaps the CPS is malfunctioning or the portion of the flywheel that the sensor uses to determine crankshaft position is loose or damaged. There is an encoder ring on the flywheel which the sensor uses to pick up position. If the flywheel is loose timing may be fluctuating. Maybe Kris or Forde can add some insight.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #12
cps did ohm out ok but guess doesnt mean couldnt mess up after heated up.

jungleman, i will try your suggestion on tps. Idk if this means anything but when pulled throttle body to clean it had a black greasy build up on engine side of flap
Dont believe tbap harness has ever been changed from looks, as its not my bike. May be good idea to change regardless if such common problem along with pleated intake boot.

will be this week before can look at it
 

·
Registered
Joined
·
6 Posts
Discussion Starter #13
Sorry guys but I never got to fix the bike. Hurricane Harvey flooded it out and insurance took it. Just wanted to finish my post and give thanks to the guys helping out. Wish I had a solution for everyone!!
 

·
Registered
Joined
·
387 Posts
Too bad, it would have been interesting to find out what the actual problem was. Hope your damage wasn't topo bad.

Mike
 
1 - 14 of 14 Posts
Top