Hello everyone - new to this forum, but have been a lurker for awhile, researching the issues on a 2006 Sportsman 800 Twin EFI and looking for some additional guidance as I am stuck....

Background: 800 twin has only 1200 miles, picked up used. Have two other sportsman 500's which we use daily on the ranch, one with 7K+ and the other w/10K miles. They get full fluids change out every winter and other scheduled maintenance (plugs, wires, brake/boot inspections etc.).

As I did not know the maintenance background on the 800 twin EFI, I changed all fluids per usual, but was still running "rough", rich on the fuel side (exhaust), poor to no idle, but when I gave it full throttle it has full power, no stuttering, surging etc.. Checked codes and 41/45 came up, Replaced the TBap sensor and wiring harness and cleared the codes. Ran better, but still not where should be.

Previous owner changed the spark plugs/fuel filter due to rough running. I removed the spark plugs, set proper gap (0.035) and installed new spark plug wires as they didn't ohm consistently nor snap in place properly and also cleaned the throttle body plate, checked the boots etc. (all fine).. Also ohm'd the coil which came in @ 636 Ohms, slightly above the 560 +/-10%, Idle has settled in @ 1080, no rich smell on exhaust BUT...still hesitating/surging when constant throttle applied (power, no power, power, no power)....HOWEVER...when I give it the nuts (full throttle), she goes no problem, no backing off, no loss of power, just constant climb on power. When back off to constant throttle position, back to surge, hesitate - may settle in @ 2900-3200 RPM, but then if back off or press slightly, back to same surge. I am running 91 octane w/a can of seafoam in there, but don't believe fuel/injector problem, spark problem.

My gut says TPS (throttle position sensor) which is a dealer deal. Thoughts on this or links to how others may have solved it (other threads)?

Any assistance would be appreciated.

Thank you - SDman

 

Update: purchased testing harness from Amafun (cheap $12 harness w/proper end connections) and hooked up w/out the 9V battery (Dealer testing deal). Turned key on and Red/Black lead was 0.73V, steady rise as press on throttle to 3.8V. No jumps, surges way up or down. Green/Black showed 4.99V with no change when pressing throttle. Red/Green was 4.26V, steady decrease to 1.18V. Again, no jumps, surges way up/down. The way I read section 4.16 of the Maint. manual, the TPS is reading properly and working properly.

Next steps are to dig in and read more in depth on chapter 4 in general. It's an engine - fuel, spark, air....unless something is grounding out somewhere playing havoc with the ECU/EFI.

Still stuck and open to ideas......

Thanks - SDman

 

2004 Polaris 700 EFI Cutting Out & Surging

in polaris forum check out above thread.Not sure how to link to it. His was doing the same and it was fuel filter

 

Hammer,

Appreciate the reply.

I saw that thread, but unfortunately the main filter was changed out. Don't know about the one in the tank or how it looks, but I've got power no problem when I give it full throttle (no cut out/hesitation -> constant climb). 1/2 throttle is the issue (low or constant RPM say 2000-4500 ish, just not mashed down)

I've checked the fuel pump - constant 39 psi pressure/volt measurement. I checked the crankshaft position sensor and ohm'd out at 572, runnout was good along w/positioning, air gap etc. Ran through the harnesses and took out for a spin to check fence, same deal on the surging. However, when got back on it, restarted....smooth as butter, good idle...time to noodle.

1. When starting cold, very very rough ldle...like it won't idle, just will die, thus have to put into H and have thumb on throttle to keep running and then start driving immediately.
2. Once driving, still hesitates, surges, etc. etc. Drive it long enough and then shut off to do some fence mending (short amount of time, thus engine still warm). When started back up, idle no problem, settled in right @ 1150.
3. Drove back and no hesitate/surge etc. just smooth as can be. Stopped again to check another gate/fence and when restarted, same thing....idle settled in and when driving, smooth as butter.

I don't think fuel pump nor injectors based upon the temperature deal. If was lose/bad Tbap would see it cold and warm engine (no codes either).

So, based on the above I replaced the temp sensor..... No dice. I just replaced the injectors/wiring harness for them. Still not 100% certain on the operation of it. I'm going to keep digging until I find it. Still might have to do with rough idle when cold, but will when it is warm. The other two idle no problem - cold or warm.

Any thoughts?

SDman

 

I am guessing first year they went to EFI . No carb. It sure sounds like a fuel problem as it works when warm.Something is opening up when it is warm and staying closed when cold. You have ruled out the fuel pump so I am at a loss................. Can you disconnect it see how it pumps when cold and then do the same when warm? This has to be something simple. They are such good machines. I am on my 3rd one.

 

Hammer - my thoughts exactly, after the engine temp sensor replacement, that something is opening up when cold, expanding when warm and sealing - it was the main boot on the down stream side of throttle body, connecting to the piston/injector intake. Tight taking off, dirty on the face, didn't look like any gasket. Cleaned up both faces and applied some red RTV gasket maker. Got everything back together....purrs like a kitten.

RE-CAP:
ATV-RED - Notes - 2006 Sportsman 800 Twin EFI
bought used, 1200 miles

General symptoms:
- will not start on 1st crank, but will start on 2nd crank if throttle applied
- will not idle when cold - to keep idle, must have thumb on throttle switch
- when cold, will hesitate, surge with constant throttle, but if full throttle, no surge, steady climb on power
- when warm, will start straight away
- when warm, surging for most part (95%) goes away with steady throttle.

What have done:
- former owner put in new plugs. I checked and regapped to 0.035 per settings.
- replaced plug wires as one ohm'd bad and did not connect properly. Ohm'd coil, came in @ 636, slightly above 560 +/- 10%. runs better, but not where should be. Checked continuity - good
- former owner put in new main fuel filter. Have not checked to see if issue or not, but don't think so if full throttle with no surge.
- former owner ordered new Tbap sensor as thought was issue with codes 41/45 coming up. Replaced sensor and wiring harness due to lose ends. Checked continuity - good. Runs better, but not where should be
- checked fuel pump - constant 39 psi. Checked continuity - good
- checked crankshaft position sensor - proper gap, runout and ohm'd out @ 572. Checked continuity - good.
- replaced fuel injectors/harness with new injectors/harness. Runs better, but not where should be. Checked continuity - good
- checked engine temperature sensor - ohm'd out 2.4K, 0.187k +/-2% when hot. Replaced w/new anyway. Checked continuity - good
- checked TPS - gap up top on throttle is normal. Measured voltage to TPS and came in @ 0.71 with a 4.99-5.00V reference. Cleaned throttle body plate/throat - not much fouled
- pulled main boot from outlet of throttle body (connected to piston/injector intake - good, but dirty connection. Cleaned up and made gasket of red RTV.
- Cleaned oil breather plate and retightened.
- Cross checked oil pressure pressure relief piston/spring to make sure not hung up.

Put back together this afternoon (rain day) - runs perfect. Took out into the pasture - no issues at all (idle, constant throttle, cold start etc.). Key believe is boot between piston/injector intake not sealed, thus why poor performance cold vs. warm via excess air beyond Tbap sensor.

Hope the synopsis helps someone else.

SDman

 

Congratulations on figuring out difficult problem!

 

UPDATE - 2025-04-25 - thought I had it fixed......
Been putting the 2006 Sportsman 800 EFI to work on the ranch. Would still not idle and run rough initially (surging, hesitant etc), but once warmed up (really warmed up), ran great, smooth acceleration, no hesitating/surging, just ran normal. But if cooled back down, it would go back to old habits. Something still not right, but right when warm.

Since we've had some rain days delaying other chores, figured I'd give it another go. Knowing I had replaced Tbap, thermal, injectors and sealed intake/boot and maint noted in the above thread, something else. Observed - still no idle cold and very touchy initially on throttle...like sensing to much throttle (too much fuel vs. air), though barely applying any, but when warmed up, idled fine and throttle response I would consider normal, consistent, smooth.

Tore back down and used TPS harness to check TPS potentiometer and seemed to bounce, not consistent. Is also located right next to exhaust manifold, thus maybe "getting itself right" when warms up. So, replaced.

Did not follow procedure in service manual to take back to base level voltages as this one has a "D head" screw for throttle plate adjustment screw and didnt' have the tool and looked like loctite had never been moved therefore figured had not been adjusted since factory, thus default back to assuming factory voltage was @ 0.528 +/- 0.001, thus only needed to adjust TPS angle to 0.710 +/- 0.001. Lots of fiddleing on the adjustment to get voltage correct as I must have a magnetic personality (if touching, different voltage vs. if not).

Rough reassemble and just took for a test drive just now...idled right out the chute, cold start. NEVER had that before. Driving was smooth in Low or High, no matter where had thumb on throttle. Smooth acceleration, no bogging, no hesitancy, surging etc. just smooth operation. Think this is the fix. Time will tell, but happy.

Hope this helps someone else.

SDman

 

Just for future reference, red RTV is the incorrect silicone to use on an intake it fuel system. It can mess with the TMAP censure and or the IAC valve.