Help diagnosing crappy idle/poor low end

mickyd32 · Dec 20, 2016

FIXED!!! Help diagnosing crappy idle/poor low end

Hey guys end of last season my sled started running like crap. Basically a poor idle, and low rpm to 6500 it's a dog then after that it's fine. Not sure what it might be

I did a compression test just to rule that out. It's 125 per side on 2 pulls cold

What else might it be? Tps out of whack? Bad injector? Reed?

I am getting a code for a bad pipe sensor. But I was getting that before the crappy running

Sled is a 2013 pro 800

ripalip2 · Dec 20, 2016

need to read threw the write up about tps adjustment and make sure that's right first

Drewd · Dec 20, 2016

Most obvious issue is the EGT sensor in the tuned pipe. Perhaps it was slightly out of spec originally when you got the code but has gotten worse and is way out of spec now.

I'd replace it before looking at anything else or you could be chasing your own tail.

If EGT sensor doesn't fix it, I'd look at the following from easy to not so easy:

1. Exhaust valves. Check to make sure they aren't stuck and no tears in bellows. An open exhaust valve(s) can make engine run like a dog.

2. Check for airleaks in boots.

3. Check back on this forum thread to get answers from someone who knows what they are talking about.

mickyd32 · Dec 20, 2016

I have a new pipe sensor here. I will try that after I check valves. They are due for a cleaning anyways

I have a pcv on it. I can easily check tps when I get the laptop to the shop

mickyd32 · Dec 30, 2016

update

so I started with the pipe sensor hoping for the easy fix, code cleared but no change in the running of the sled.

pulled the exhaust valves and cleaned, dirty but no issues with them, tried sled again, no change in outcome still dead on one cylinder

next i pulled out the laptop and hooked it up to the powercommander. Resent my mapping and checked TPS. TPS was out but not enough to make it run like it was. Started the sled again, no change

Out of easy things to check, I did a compression test. Cold 3 pulls was 125 a side. Warmed it up and checked 90 psi clutch side and 125 mag side

Pulled the tools out and rebuild the top end. Found a stuck ring on clutch side no damage to the pistons or the cylinders that i could tell with the naked eye so I rebuild it with new pistons rings and gaskets

fired it up and again no change still not running on the clutch side (not that all the way through it runs good above 6000 rpm and like a dog from idle to 6000) also temps with my heat gun are 150 mag side and 85-90F on clutch side

so I decided to change the injector on the clutch side with one we had from and engine that tossed a rod. (same part number injector) so I split the harness and changed injectors (note that there is fuel in the rail on both sides so there is fuel to the injectors) Fired up the sled and got the same result

Next I pulled the stator and changed it out runs a little better but not what it needs to be

What does that leave me? a bad injector wire, bad computer? any other ideas?

the next easiet thing to do would be buy a new injector harness, assuming its in the harness and not past that

would love if I had digital wrench and could see what it said lol

omernikski · Dec 30, 2016

Bad coil pack?

mickyd32 · Dec 30, 2016

Sorry. Forgot that one. Also tried 2 different coil packs off a running sled. Same result

TRS · Dec 30, 2016

Unplug the PCV and see if that fixes the bottom end.
Did you check the cylinder EV ports? Make sure one isn't plugged. Why I Question that, 125 each hole cold and 125-90 hot.
A leak down test is in order next.
Need more info also, head-pipe-porting-so on.

omernikski · Dec 30, 2016

Digital IC error code display

mickyd32 · Dec 30, 2016

omernikski said:
Digital IC error code display

There are no active codes

omernikski · Dec 31, 2016

Did you check your VES solenoids? Make sure that the hoses arent plugged, the valves are closed when not powered. If a valve is stuck open it will exhaust cylinder compression. Check fuel injector power, should be 16V.

mickyd32 · Dec 31, 2016

I replaced the discharge hose off the EV solenoid (I have a longer one installed into the shock tower so its not constantly pissing oil intoi the belly pan) I will check the inlet side to the solenoid

I will have to check the supply power to the fuel system. Could it also be low fuel pressure? I was thinking if there isn't a high enough pressure maybe its only feeding enough fuel to the exhaust side and not to the clutch side
There was fuel in the rail but not sure fo the pressure

Also for the ones asking its a SLP stage 3 kit on the sled, (pipe, head PCV)

Sled has 3400 miles

omernikski · Dec 31, 2016

Do you have enough hose to plumb the clutch side ev solenoid to the mag side cylinder and see if the clutch side starts firing

TRS · Dec 31, 2016

mickyd32 said:
I replaced the discharge hose off the EV solenoid (I have a longer one installed into the shock tower so its not constantly pissing oil intoi the belly pan) I will check the inlet side to the solenoid

I will have to check the supply power to the fuel system. Could it also be low fuel pressure? I was thinking if there isn't a high enough pressure maybe its only feeding enough fuel to the exhaust side and not to the clutch side
There was fuel in the rail but not sure fo the pressure

Also for the ones asking its a SLP stage 3 kit on the sled, (pipe, head PCV)

Sled has 3400 miles

3400 miles and has never been apart????

First thing, do a leak down test. I'll bet it fails big time.

mickyd32 · Dec 31, 2016

ya I have plenty. Unfortunately I'm 22 hours away from the sled so its going to have to wait a few days

Scott · Dec 31, 2016

What do the reed petals look like?

Put a stick in the exhaust drain and plug it up tight...does it run better or worse?

omernikski · Dec 31, 2016

He just rebuilt it but i suppose that doesn't rule out a cylinder out of round. Has to be something fairly simple

mickyd32 · Dec 31, 2016

Looked at the reed pedals when we did the rebuild. They looked good. Nothing cracked or missing

mickyd32 · Dec 31, 2016

Also as for the 3400 miles remark, this is the third top end. One was done on warranty at about 17-1800 miles

omernikski · Dec 31, 2016

Hopefully all the insite offered is good and its a cheap fix

Help diagnosing crappy idle/poor low end

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