High idle or surge in idle - Harley Forum

unfknblvbl · #1 06-22-2009, 05:52 PM

Anyone have any thoughts or ideas on the problem below throw them out:

If my bike has sat for a day or two and I go to start it, it will either idle really high (don't have a tach but if I was to guess I would say in the neighborhood of 2k rpm's or better) or it will start to idle as it should then start to surge really bad. The surge is almost to point of dying and then it will come back.

My initial thought is bad gas. The first time it did this it had probably been 2 or 3 days since I last rode and right before I parked it I topped it off with gas. I haven't emptied this tank yet, but worked on emptying it yesterday to see if that was/is the problem. The station I got gas at I have never got gas there before that is why I came to that conclusion.

My next thought was an air leak somewhere. I took the stock a/c cover off and ride with an open filter (which needs to be changed and will be Wednesday when my K&N arrives), but I can't really attribute it to that because I took it off a while back and this problem just started. Unless the filter is just so dirty it's having a hard time breathing, but again there I wouldn't think it would keep running. We haven't had any rain or dew build up and my filter is not wet.

Now if I start it and I am having one of these problems I can kill it and start it again and that will usually fix it. Sometimes I have to kill it 2-4 times and that will fix it or if I've rode for a while and make a pit stop it will start up just fine.

The only sort of electrical problem per se I've had in the past is draining the battery, but I put a new battery in it and double checked my fuelpak to make it retained it settings and that was good.

Any type of fuel additive/injector cleaner I could throw in the next tank to kind of clean out the system.

Gas Man · #2 06-22-2009, 08:03 PM

I'll only comment on any additives...

Try SeaFoam for ruff running, winter storage, and so much more

unclepsycho · #3 06-22-2009, 09:04 PM

Hey Unf...

I cant remember what your bike is, but that sounds exaclty like what my wifes, Jeep was doing. I know, I know, It aint a bike... but it is a Fuel Injected Gasoline engine. and it turned out to be the TPS...Throttle Position Sensor. Does your bike have one of those>???

Her Jeep did that the way you describe... fast idle, then ok. then rough, then fast again, didnt matter if it was warm or cold, it was random and intermitten but when I changed the TPS it came back to normal.

unfknblvbl · #4 06-22-2009, 10:54 PM

Yo Unc, good call man. It is fuel injected (08 Night Train) and think a TPS is pretty much standard on any fuel injection. Hard to tell without my service manual though. I got a buddy who is a tech for a stealer. I'll give him a call and ask, I just don't like the telephone.

Next would be, if it is, I wonder why it would go out so darn quick. I've had my bike just over a year now and it only has 7,600 miles on it. Hhhmmm

unclepsycho · #5 06-22-2009, 11:04 PM

The TPS is made by Humans... so there's room for Human Error... ha ha...

The code that the computer threw was that there was a voltage problem with 2 or 3 injectors, on the v-8 jeep. I swapped the injectors around and the computer still pointed to the same 2 or 3 injectors... so I looked at what told the injectors to fire and that was the signal from the computer based on the TPS position. thats why I replaced the TPS..... The code reader didnt tell me it was the TPS, but it fixed the problem. That was 6 months ago and about 10k miles, still runs fine. I guess cars and bikes computers kinda run on the same logic.

Good luck, let me know what works..

coconl · #6 08-10-2009, 09:10 PM

I had a car that did this and it turned out after many times in the shop that the throttle body wasn't closing completely and it was causing the engine to surge. Its the same principle with the HD fuel injection.

steve dennis · #7 08-23-2009, 11:35 AM

My riding buddy had the same problem on his 98 RoadGlide. Turned out to be the air intake sensor. A pain to change,but the problem went away.

harold · #8 11-18-2009, 08:21 PM

I had the same problem at one time, i adusted the throttle cable by the book and it went away. i also noticed at times my throttle cable lages and the cable didnt do this till i started using minox to lube the cable.
to be exact , i didnt have the surge problem the bike would just high idle for some reason not by alot but perhaps 1500 or so, im guessing because i dont have an rpm guage either.