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Old 09-23-2007, 09:41 PM   #1 (permalink)
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Rough idle all of the sudden - any ideas?

I am hitting the wall trying to find the root cause of a rough idle problem that recently surfaced about a week ago and could use any thoughts you have on what else to look for. It starts fine and was idling great previously. Now the motor really jumps around during idle (set to 980 RPM)...sometimes smooth, sometimes really rough, most of the time rough. No codes were thrown during or after the problem.

05' RK - 510 chain drive cams (06-07 cam plate design), high compression SE 103 top end, T-Max, closed-loop with 2 sensors. I do all of my own wrenching.

Here's my list -
1. Broken front motor mount? - Replaced with new mount; no improvement...
2. Manifold vacuum leak? - sprayed around the seals with engine starter and detected no RPM changes
3. IAC motor not moving? - pulled the air cleaner and watched the plunger move when initializing the start switch...don't know if it moved as much as it is supposed to...or is intermittent...closed the small air port with my finger and the RPM dropped instantly indicating that the port was open as it is supposed to be..
4. Leaking injector? - oberved down the bore of the throttle body while turning the fuel pump (the systems) on and off 5 times...observed no fuel flow into the throttle body...
5. Connector or wire issue? - Pulled the tank and checked the wiring and plug ends on all the TB sensors...observed no issues
6. Loose push rod? - Checked all (SE easy adjustables) and they are tight.
7. Plugged air filter? - No. It is fine..

Any ideas on what else I should check or what may be causing this? THANKS!
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Old 09-23-2007, 10:53 PM   #2 (permalink)
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possible wet sump issue fouled plug
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Old 09-24-2007, 03:59 PM   #3 (permalink)
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Only other thought is the dreaded broken injector wire inside the insulation. Pull on the individual wires at the injector connector while running to see if trouble is related. Many times the wire and insulation will pull apart with only slight pull on the wire.
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Old 09-24-2007, 04:01 PM   #4 (permalink)
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Throttle Position Sensor
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Old 09-24-2007, 08:27 PM   #5 (permalink)
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Quote:
Originally Posted by Otto
possible wet sump issue fouled plug
I took 12 ozs out of the sump when the engine was cold. It seems like more than I measured last time I did this. Is this too much???.
It seems to me that the rough idle problem is the worst when I come off a high speed run like coming off the freeway and idling at a stop light. If it's a sump issue then wouldn't it be the worst at this time? I just drained the sump completely. If I start it up and it comes up to temp with a smooth idle then I take it our for some speed and the problem comes back then this may confirm this problem.

Maybe that little S&S reed valve assembly down in my cam chest is aggravating this??...Latus motors has some testing that showed the S&S reed valve causes wet sumping in some motors...

http://www.latus-harley-davidson.com...ts=40&mid=1430
another one...
http://www.latus-harley-davidson.com...1&mid=834#M834


...plugs were fine but I am running a little rich...may take it back a little...
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Old 09-24-2007, 08:28 PM   #6 (permalink)
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Quote:
Originally Posted by PR3VS56
Throttle Position Sensor
TPS measures right where it is supposed to be and seems stable...however, anything here could be intermittent...
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Old 09-24-2007, 08:30 PM   #7 (permalink)
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Quote:
Originally Posted by HAWGZILLA
Only other thought is the dreaded broken injector wire inside the insulation. Pull on the individual wires at the injector connector while running to see if trouble is related. Many times the wire and insulation will pull apart with only slight pull on the wire.
I peeled back the insulation on one injector lead I suspected and it was fine...following a lot of pulling and wiggling looking for the dreaded "sometimes open"...
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Old 09-25-2007, 12:08 PM   #8 (permalink)
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This morning I started the engine after draining 12 ozs from the sump last night and it idled rough to start with. After idling for about 3 minutes I stopped the engine and drained the sump again; 8 ozs came out this time...a little more than I want and probably due to the S&S reed valve in the cam chest. I don't think the S&S reed valve is causing the rough-idle problem but it is going to be removed later.

I also checked warm engine compression and both cylinders read 190 PSI, (open throttle), 160 PSI (closed throttle). Still haven't found the root cause yet...!!..
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Old 10-09-2010, 03:52 PM   #9 (permalink)
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I have same problem did you find any solutions?
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Old 10-09-2010, 06:48 PM   #10 (permalink)
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Go to the gas station with a clean gas can and fill it.

Drain your gas tank and fill it with the new gas.

Both you guys are on the left coast were alcohol in the gas many times runs at higher concentrations (above 15%) and plays havoc on you ECM tune.

just happened to a bike that came in about 4 weeks ago and I was pulling my hair out.

hope this is your problem
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Old 10-13-2010, 11:17 AM   #11 (permalink)
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Got the same issue and just can't seem to put my finger on it. Pulls OK but sometimes it just feels rough at idle. Also have the T-Max and a set on Andrews 21 on an 06 TC-88 with K&N air cleaner and supertrapp exhaust (14 Discs installed). Can't figure out also why is is smooth sometimes and rough others. Doesn't seem to miss but just seems it's just not running smooth. Not that it's really smooth otherwise. Checked also all the obvious (injector wire, fuel pressure, etc....). curious what anyone else finds.
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Old 10-13-2010, 06:07 PM   #12 (permalink)
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possible pin hole in high pressure fuel injection line inside tank ,just a thought.
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