01 Ultra with Stumble Problem

Sometimes problems drive you nuts, this ones been an issue on a friends bike, it was so bad at one time he was selling it. I got 90% of it taken care of but the last 10% is driving me nuts so here's the issue, see if you can come up with a solution.

01 Ultra
stock heads, intake and cyl
tw37B cams (previously SE211)
HD Stage 1 filter and backing plate
Rienhart true duals

When started the bike starts fine and idles ok, not really too high but it will hold steady idle. It never really seems to idle up and down like an EFI should, it just goes to a steady idle, then you have to remember it's in FL so it's not like it's really cold out LOL

When you take off to ride, until the motor is really warmed up it will stumble under 3K RPM, if you whack the throttle open it will pull through the stumble and above 3K no stumble.

Once warmed up the lower RPM stumble is gone however in 5th you can really notice it has an slight stumble at 2700 to 3K, over 3 k it's not present. So rolling along at 65 to 70 you are in the stumble band. Almost like a surge/stumble

It has a new powercommander usb, that replaced a PC 3 and that replaced a DFO, all of these had the same issues only worse.

Previously I replaced plugs and plug wires (one had a cut that was shorting the front cyl out) that helped and the engine temp sensor has been replaced.

It has good solid intake seals, no exhaust leaks, motors never been apart, sure has become cold natured as well.

the PCUSB has a custom dyno map built for the bike.

Thanks I'll do some of that testing this evening, it's not tossing a code for any of the issues, I did put a new temp sensor in the motor about 6 months ago,

It along with the plug wires that were cut and shorting out the front cyl along with a frayed wire and broken connector on the VR were replaced this cured the bad running motor.

I agree it may be in the tps or cold start area, I'll check that this evening.

Haven't pulled the injectors, I was wondering if maybe a loose injector wire could be a problem. However the seals around the injectors look good and it's not an abused but, normal wear though.

The stumble at cruise seems to be more of an RPM thing, I'll ride and check 4th gear at 27 to 3K and see if it is consistent.

I know it's below 3K due to the cold and hot issues.

BTW I don't have a manual for this bike but if you can scan and email the pages or fax them let me know also the tps procedure for checking hot and cold with the VOM.

Thanks for the book offer however I dont want to put you out on mailing it as the bike will be going back to him in a week anyway.

I think what you've given me is a good start, I can get the guy to go buy the SM at the local dealer, I've suspected a bad IAC or hot cold idle problem funny thing is two dealers and a indy couldn't detect the problem.

It did have so many other issues that it was masking the cold and tps issue.

It had a cut front plug boot arcing to the cyl when it got wet it just went nuts

Rear plug wire had worn through on the frame

Temp sensor wire was exposed and worn through from being routed over the top motor mount adjuster threads.

VR housing connector was cracked and exposed.

Speedo sensor was out, LOL

Lot of little things.

I will say when it's on that little 88 with a cam will flat pull hard.

I'll post some results tomorrow or Friday.

Pulled backing plate turned on ignition and the cold idle plunger moved forward as it should and retreated just a bit, turn it off and it returns to the stop position so that seems to be fine.

checked vdc across A-C, at idle it's .74 and runs smoothly up to 4.70 at WOT at least digitally I didn't see a spike

.74 seems high at idle doesn't it?

Will do thanks maybe that will fix this puppy back to normal.

Ok went home for lunch adjusted TPS to .031 right in the middle bike starts fine, haven't been able to crank it up to see about the 2700 to 3000 issue but
now it has a surge when you hold constant throttle.

Neighborhood is 30 MPH and holding it there, or at 25, or 35 steady the bike surges vs running smooth as it did before.

Not yet just doing one step at a time.

When I set it at .5 that problem isn't as bad

The issue at 2700 to 3K did go away it's like I just moved the issue into the 2200 range.

Its a PC USB and no I have not matched it as of yet.

It does feel like a lean surge, it's almost as if when you move the voltage down the surge that was at 27 to 3000 moved down into the 2000's with it, I was going to move it down to the lower setting of .2 and see what happens this evening.

Yes on the baro sensor if you can tell me what to look for and what pins I can test it.

Here's what I was thinking of doing tonight see what you think

1) Remove ac and backing plate
2) Back off idle screw from touching plate
3) open plates and clean EFI throttle body and plate ends to be sure we have a clean surface to work with,
4) Set TPS to .3ish
5) Set PCusb idle position
5) Close warm Idle screw to touch plate lever

6) Start bike and adjust warm idle to proper rpm.

See if that will clean up the stumble down under 2500

thanks that sounds like a plan for this evening,

The stumble was there before the pc, it's got something somewhere going on and it won't set a code, one of the "find me problems"

I'll let you know how all the tests and numbers pan out.

Was out last week and didn't get around to the bike,

The ECM was replaced by an indy shop as being bad, I always suspected this was wrong, and in that the bikes current problem was still there I met up with him on Sun and got the stock ECM.

Replaced the replacement ECM with the stock ECM, set the TPS at approx .25 and reset the throttle position on the PCUSB.

Thank god for wireless internet, had to download the latest software, easy to do sitting in the garage.

Anyway it fired right up, idle cold never seems to go up but the plunger moves, I have hot idle at 1100 right now and it runs good, the stumble is gone and it accelerates briskly.

I'll drop the idle down about 100 or so tonight its hovering just over 1100.