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Engine misfires at low speeds

Engine, Fuel and Exhaust

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Old Mar 27th, 2012, 06:25 PM     #11
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Re: Engine misfires at low speeds

Possibly a sticking fuel pressure regulator, or an intermittent fuel injector wire (at the injector). You really need to do a fuel pressure test. It should not be too expensive to have it done at your local dealer or indy.

Enjoy,
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Old Mar 27th, 2012, 06:27 PM     #12
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Oh - should have added that I tried the method on checking for leak in the pressure side fuel line posted by Mr. Data for in "Engine Dies and runs in spurts". I ran the fuel pump, but before I started the bike, I pulled the fuel pump fuse. The bike started normally, ran for about 10 seconds and then slowly started to stall. Assuming I am reading it correctly, if the line had a leak the pressure would bleed off and the bike will not start.

=================================================

Rich ... does my compression of 130 sound about right?
thanks

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Last edited by Dr. Dolittle; Mar 27th, 2012 at 09:04 PM. Reason: merged posts
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Old Mar 27th, 2012, 07:06 PM     #13
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Re: Engine misfires at low speeds

Quote: Originally Posted by classic02 View Post
I have noted exhaust smelled rich when sitting at stop light or idling and also poor gas mileage
A couple other comments - cruising between 2000-2500 rpm (really about any gear), the motor acts like it is running on one cylinder. As I get up to about 3000 it is running nearly the way it should. Also, the problem is a little worse when the motor is warmed up ... once it is up to temperature, When I roll throttle a little, the engine starts to cut out then picks up and accelerates smoothly with no indication of misfire or power loss.
If fuel pressure checks good, a lot of those symptoms are starting to point to TPS and/or Map sensors. Not hard to check but once again, need some tools. Don't depend on firmware diagnostics to catch it.
Here is a picture.
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File Type: pdf Map&TPS.pdf (53.8 KB, 32 views)
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Old Mar 27th, 2012, 07:08 PM     #14
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Re: Engine misfires at low speeds

Quote: Originally Posted by classic02 View Post
Rich ... does my compression of 130 sound about right?
thanks
Both Cylinders? That will work
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Old Apr 6th, 2012, 05:38 PM     #15
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Re: Engine misfires at low speeds

Here is my (unhappy) update - took bike into dealership, gave them a write-up with the info about everything I had already tried and what to check next (fuel pressure followed by TPS/Map sensors). They thanked me for info and assured me they'd use it. Just got bike back and they told me I had an intake leak - not sure how they tested it, but they said the seals with hard/bad. They said it was much better, but weren't completely happy with it so they also did some tuning with the DFO to improve it (said it helped the decel popping). I asked if they checked the fuel pressure as indicated in my notes (and requested verbally with service mgr). Told me no, but that there was no indication of a fuel pressure problem. Rode the bike home and I can hardly tell any difference - I don't think the new intake seals or tuning helped. Sputters and pops just as bad. Called them about it and they want to make it right ... offered to do some more "tuning" on the bike. They questioned if the DFO was bad (I had previously told them I unplugged the DFO and there was no difference in the problem). They said they would document my fuel pressure too if I wanted that info. Maybe time to try another shop.
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Old Apr 6th, 2012, 06:54 PM     #16
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Re: Engine misfires at low speeds

its all about the money boys
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Old Apr 6th, 2012, 10:11 PM     #17
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Re: Engine misfires at low speeds

I'm going to stick my neck out here. And this is a stretch.

I went through a somewhat similar problem on my 03 RKC. However, I did have the holes in the fuel line. I changed the lines, filter, plugs, sensors even the fuel pump. Same problem afterward, high idle sometimes, acted like it was missing, sputtered at low to mid speed....on the higher speeds, I think I was ok. ( could have been mental )

I bit the bullet, took her in. It took them two days to find it and only after I went in to tell them what I did previously. I told them i changed out the TPS sensor ( and showed them). When i pulled the TPS sensor, a small shaft came out. Well, that shaft wasnt supposed to come out. It was my Intake Body Shaft. It was cracked in half and the TPS sensor was holding it in place making it almost invisble to the eye.

Its the shaft holding the "butterfly" in your intake. Thats what was snapped in half. Put a new one in........better ever since. $300 at the shop, parts and all.

just a shot in the dark....good luck

you live, you learn
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Old Apr 6th, 2012, 10:34 PM     #18
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Re: Engine misfires at low speeds

Quote: Originally Posted by Amish Hawg View Post
It was my Intake Body Shaft. It was cracked in half and the TPS sensor was holding it in place making it almost invisble to the eye.
That's a very good possibility. It has never happen to me but I have read that it happens more than one (at least me) would think. That would sure do it. Good call.
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Old Apr 7th, 2012, 10:20 AM     #19
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Re: Engine misfires at low speeds

Sounds like I can check that out myself ... if shaft is OK, might it be worth trying a new TPS? I have read in some other posts about TPS problems in certain ranges of throttle operation. I also noted on an the jet kit instruction sheet from Dobeck that under troubleshooting, they list "loss of TPS and ECU sync" right after intake leak as a possible problem (actually high lift cams are next but not applicable in my case).
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Old Apr 7th, 2012, 10:54 AM     #20
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Re: Engine misfires at low speeds

The TPS takes about 49.6 seconds to replace, its that easy. Just two philips screws. Where it mounts to the intake is where the shaft is. Mine was cracked exactly where the "butterfly" ( I dont know the term ) wrapped around the shaft. when the TPS was installed, there was no way to see it. When I showed them what I did, I actually took the TPS off again and the shaft, part of it, came out.

Everything else I did to find this mess.
Cleaned out the IAC
Checked the wiring for cracks ( fuel injectors )
changed the TPS
Changed the plugs
checked the coil
changed the spark plug wires
Checked for intake leaks
Changed everything about the fuel system - NOTE - I didnt hear the hissing when I listened for the fuel line holes. Grab the Manual go in and look. Its really pretty easy to do a visual, plus you can change out that fuel filter that maybe hasnt been touched since inception. buy some worm clamps, for the hoses. Be careful with the fuel pump......I broke mine when i took the hose off ( bonehead move ). When I removed the fuel assembly, I found three holes in the hose, a bad fuel filter...it was like tar in there. I didnt know any better, so I went to the dealer to get the parts.....roughly 150. I got a fuel pump from Bud's in Austin for 130.

What I am saying is this: Grab a sixer of your favoorite beverage, turn up the tunes a tad, open the manual and expect to spend a few hours doing this. Always good to work with a friend. I had my two boys help, they now know Harley fuel systems. TAKE YOUR TIME

Maybe the shaft problem was a "fluke" that it happened......it was a tad frustrating.

I'm telling ya, stay on here and walk through it, these folks on here will find the problem. I'll buy the first round if I ever roll up on any of them.

So far, I've rebuilt the fuel system, clutch, inner/outer primary,brakes, tranny seals and oil seals just by asking on here. And you'll appreciate your scoot that much more too.

Hope it helps.........There is a scooter screamin my name....I gotta roll.

PS - if you do take it in.....you'll save at least 100 going to an Indy, but have faith in that Indy before you do.

Last edited by Dr. Dolittle; Apr 7th, 2012 at 03:59 PM. Reason: moderator edit
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