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Discussion Starter #1 (Edited)
I'd like to put my mind at ease with my 2012 Ranger RZR 4 800 EFI/EPS and what I think might be an issue with hesitation/bogging when the engine is cold. I'd like to know if this is normal behavior or if something is wrong. I'm including a video link that demonstrates the hesitation. You'll notice the struggling, low grunting engine noise and slow start until it hits about 3500 RPM and then it takes off.

RZR 4 800 Hesitation Demo Video - Full Throttle (Google Photos)
RZR 4 800 Hesitation Demo Video #1 - Normal Acceleration (Google Photos)
RZR 4 800 Hesitation Demo Video #2 - Normal Acceleration (Google Photos)

A few key points:

  • The issue is really apparent when the engine is cold
  • Hesitation lasts for about 2 or 3 seconds when punching it, sometimes more
  • I don't necessarily need to 'punch' it either, it happens when easing up to speed as well (lasts longer)
  • I have a new belt on it, properly broken in
  • Fuel pressure was recorded at 39 PSI (consistent, idle and driving)
  • TPS resistance tests all passed
  • Throttle body has been cleaned
  • Fuel injectors have been cleaned
  • Issue persists without air filter installed (quick tests on the street)
  • Lucas fuel system cleaner added to fresh gas
  • New spark plugs
  • New air filter
There were a couple of notable outings where it seemed to really be a problem:

  • Once, at about 10k feet, after breaking for lunch, the machine would not 'break out' of the bogging/hesitation (even with holding down full throttle) and only inched forward slowly until I threw it into neutral, rev'd it up a few times, and then put it back into gear. Like clearing out your throat before speaking.
  • Might be separate issue: Engine warmed up after a big ride. Heading up a mild incline on a dirt road, in high gear, flooring the gas I was only going 30 MPH.
I'd appreciate any help or advice you guys have to offer. I'm thinking that maybe the 800 is simply underpowered for the 4 seater and I'm overthinking things.

Still to come (probably later today):

  • I'd like to check the fuel filter at the pump to see if it's clogged up (I don't have the tool to loosen the pump)
 

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Is it possible you have too much clutch engagement? Does it do it in low range?

Short answer is No this is not normal, something isn't quite right. Do you live at altitude? I have 2 800's and both go straight to ripping if you go hammer down...no bog. Maybe a little when freezing cold but I always warm it up before beating on them.
 

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Discussion Starter #3 (Edited)
I appreciate your reply, rhino. Thanks.

It does happen in low range as well (RZR 4 800 Hesitation Demo Video - Low Gear, Normal Acceleration (Google Photos)). I installed the belt on my own, maybe I missed something. The previous owner mentioned it when I purchased it and just said it needed to warm up a bit. Not knocking him, seemed like a really reasonable guy and had lots of motorbikes and knowledge. I'm assuming he looked into it as well and just concluded he wasn't going to fuss with it anymore.

Is there anything I can adjust to lessen the clutch engagement for testing?

I live at about 4,500 ft (which is where the videos were recorded). I ride anywhere from 7,000 ft to 10,000 ft.
 

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I'll second not normal. I really don't know, but a couple other things to check. Clean the map sensor in the intake tube? They say to use the special cleaner, not just brake cleaner.

And you said tps passes resistance tests, how about voltage tests and adjustments for proper volts at idle? Quite a bit of reading here on that.

Slack taken out of the throttle cable? I don't think that would be it, but it woke one of mine up at the top end. Couldn't believe the difference.
 

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Discussion Starter #5 (Edited)
Does this have any merit?


Edit: I'm going to say no, because I'm not in a limp mode or safe mode. I can get above 2,000 RPM and I can hit top speeds. It's just that initial push.
 

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Discussion Starter #6
I'll second not normal. I really don't know, but a couple other things to check. Clean the map sensor in the intake tube? They say to use the special cleaner, not just brake cleaner.

And you said tps passes resistance tests, how about voltage tests and adjustments for proper volts at idle? Quite a bit of reading here on that.

Slack taken out of the throttle cable? I don't think that would be it, but it woke one of mine up at the top end. Couldn't believe the difference.
Okay, good to hear two people chiming in letting me know it's not normal. At least I'm not losing my mind.

I took out the map sensor in the intake tube and gave it a good inspection. Aside from the dirt build-up on the outside and near the gasket, the tip looked excellently clean. I hit it with some compressed air while it was out anyways. I also took a cleaning rag to the inside of the boot while I was there.

I have a bench power supply, I could hook the TPS up to 5 VDC and do some testing. I'm familiar with embedded systems and sensors. I don't want to eliminate the possibility, but in my mind knowing that the sensor uses a set reference voltage (5 VDC), testing the voltage is sorta the same as testing the resistance. Ohm's law and what-not. Since it's easy to get out at this point, I might get lucky with the dealership and get them to help me test it properly, but I'd have to pay them $100 just to sneeze at it. I'll call them in the morning and see what they say.

The slack is out of the throttle cable, yeah. Good thinking.

At this point, I'm still looking for recommendations, so please keep them coming. :)
 

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Actually the tps needs to be adjusted on the rzr, while its running. All you really need is a volt meter and the right wrench for the adjustment screw. Actually I think it's a torx. So if it's been off the throttle body, it needs adjusted. Forgive me if you know that already. It's a bit tricky to get the voltage right, then the rpm adjusted, kind of goes back and forth till you get them both right.
 

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My initial reply was trying to think out of the box because it seems you have most of the standard bog situations covered, I'm not Mr RZR and have only been playing with them a short time. I do wrench a lot and most of the time with fuel injection when you have that off idle bog it comes back to the TPS followed by a vacuum leak....the only other one I have had it come back to was a charcoal canister getting flooded with gas on fill ups but we dont have that. I also don't think we have a trigger on the gas peddle like the video you showed....if we do have that function that must be through the TPS as well because I have no wires on my gas peddle, straight cable from there to the body.
 

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Discussion Starter #10 (Edited)
Actually the tps needs to be adjusted on the rzr, while its running. All you really need is a volt meter and the right wrench for the adjustment screw. Actually I think it's a torx. So if it's been off the throttle body, it needs adjusted. Forgive me if you know that already. It's a bit tricky to get the voltage right, then the rpm adjusted, kind of goes back and forth till you get them both right.
Okay. From what I understand, the steps are:

  1. Disconnect cable harness from TPS and pull back protective rubber sleeve
  2. Locate Pin 1 (TPS Signal, Orange) and Pin 2 (GND, Green)
  3. Insert conductive wire (ie. safety pin) into harness on Pin 1 and Pin 2 for attaching multimeter leads. You'll need to go through the protective rubber and slightly deeper than you'd expect. Wiggle/twist/push to seat the wire fully.
  4. Test your wire connections by setting multimeter to Ohm (audible/beep) and touch wire and the pin in harness with leads.
  5. Reconnect cable harness to TPS
  6. Connect positive multimeter lead to Pin 1, negative lead to Pin 2 (do not use chassis/body for GND). Alligator clips will really help here. Take care not to touch wires to muffler.
  7. Start the engine and return to multimeter and TPS for adjustments and measurements
  8. Loosen the two screws attached to the TPS and adjust until multimeter reads ???? (Mentions 0.46 VDC and 0.700 +/- .050 VDC in service manual)
  9. Using the instrument cluster on dashboard, you'll also want to ensure your idle RPMs are sitting at 1250 +/- 100 RPMs
The only question mark I have right now is what voltage I should be reading. My idle is spot on, and the multimeter reads 2.960 VDC. It reads 0.873 VDC on wide open throttle (WOT) (engine off). There are also no dead spots in between idle and WOT.
 

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Mine are 08s, so the numbers might be different. But to make it easy I tapped into the 2 wires further down the harness behind the seat with short leads and crimped butt splices onto them. Then my multimeter leads slip into the other end of the butt splice. I was thinking it was orange and purple but I'd have to look it up on here to be sure. And mine just has 1 screw. Pita to get to sort of. Voltage at idle is .739 I believe, but the newer ones may be different.

Fwiw, both of mine were completely jacked up when I got them. One idled at like 900, with a tps voltage in the .5s. The other idled at 1300+, and I think it was .690 or so. Now they both run correctly and the same, thanks to the info on here.

But, I don't know if that's related to your issue or not. Can't hurt to have it right though.
 

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Those voltages I gave are while running. I like 1200 rpm, .739 volts + or - a couple thousandths. The idle speed on mine is a D shaped adjustment screw on the throttle body. Real pita unless you have the right tool. I used small needle nose pliers.
 

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Discussion Starter #13
Mine are 08s, so the numbers might be different. But to make it easy I tapped into the 2 wires further down the harness behind the seat with short leads and crimped butt splices onto them. Then my multimeter leads slip into the other end of the butt splice. I was thinking it was orange and purple but I'd have to look it up on here to be sure. And mine just has 1 screw. Pita to get to sort of. Voltage at idle is .739 I believe, but the newer ones may be different.

Fwiw, both of mine were completely jacked up when I got them. One idled at like 900, with a tps voltage in the .5s. The other idled at 1300+, and I think it was .690 or so. Now they both run correctly and the same, thanks to the info on here.

But, I don't know if that's related to your issue or not. Can't hurt to have it right though.
So, did you replace the TPS sensors on both of your 08s, or did you just adjust them?
 

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Discussion Starter #14
Okay all, here's the latest.

I got back into the TPS calibration and set it to 0.750 VDC (WOT) and 2.817 VDC (Idle). To my knowledge, this is within spec. Strange that my readings seem to be backwards from all the other posts and information I've seen. It's supposed to have the lower voltage when idle. Also, I can't explain it, but before when I attempted this, the RPMs at idle shot up to 1900 RPM. This time, some how, I was able to set it without influencing the idle RPMs (they're perfect at 1250).

I reinstalled everything and took it for a test run. No resolve. Did not fix the issue.

I called up the dealership and spoke with them over the phone. Of course, they said it was difficult to diagnose properly over the phone, but it's starting to sound like a clutch problem. I tend to agree that makes sense, because when cold, there's not as much friction to turn the belt, so it might be slipping until 3500 RPM when it gets pinched down harder. When it's warmed up, it grips better.

I'm ready to move on from testing and calibrating the TPS, as I don't think it's a problem in this case. I'm not quite ready to dig into the clutch and the costly repairs I may need to take. At this point, unless anybody else has any great ideas, I'm going to table this until next summer. :)
 
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