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Poor running Low Rider

ChadF said:
Cleaned the throttle body
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But did you actually clean the IAC bypass port and worm screw pintle. You have to turn the ignition key on/off to get the stepper motor to step & park as you spray.

If you just showered the throttle body with spray cleaner, that won't do much for a sticking IAC. I had a sticky IAC and after repeated flushes, I finally had to remove it and clean it by hand with a toothbrush. Then it finally worked like it should.

But if you already have given up, let us know what the dealership finds.
 
Here is something new today. I fired it up and let it warm up and it was only running on one cylinder with the second only firing maybe once or twice for every ten of the other.
 
I had a lot of trouble with a Low Rider running poorly also. Turned out to be the plug wires. Replaced them and everything fine. Just a thought.
 
Well, here is an update on my Low Rider. I pretty much took the whole bike apart looking for anything that could be a problem. I measured the resistance of every wire in the bike. Inspected the harness for chaffing. No problems found in the harness and all connections looked OK.
I pulled the intake off, cleaned it and replaced all of the seals, no change.
I bought the Harley fuel pressure adapter from Matco for my fuel pressure gauge. It is part number HPFA502 if anybody wants one. The fuel pressure the fuel pressure running was between 40 and 45psi. As soon as the engine was shut off the fuel pressure would drop to 0 instantly. So, I fugured there was either a problem with the regulator or check valve. I dissassembled the fuel tank. In the tank I found a couple of problems. The connector for the fuel pump had a bad connection and had started to burn the connector in the pump. The line from the pump to the regulator had started to crack where the nylon tube is pressed over the fittings. So I replaced the fuel pump, filter, in tank harness and fuel pump line to regulator, which the dealer said comes with the pump, but it doesn't. You would think this had to fixed the problem, but it didn't.
So, at this time I figure it has to be a problem in the ecm, iac, injector or something. I bought the Daytona twin scan to get an idea of what was going on in the ecm. When the engine would start to miss and back fire the iac would start to rapidly ossillate between full closed to about 20 to 25 steps out and would randomly jump to about 100 steps. The miss, back fire and stall is only at hot idle. When the bike is cold idling at 1000rpm the iac is about 35-40 steps. So, I removed the iac and connected it to my ohm meter. Cold it looks ok. I took my heat gun and started to heat it up and found that when it gets hot the position sensor starts to change resistance, which I think confuses the ecm.
I replaced the iac and have riden about 1000 miles with out a problem. There is a lot more that was done but these are the biggest problems I found.
 
It is good you got the fuel pump/pressure back to normal. The bike should respond to the increased fuel pressure.

But for the life of me, I sure can't come up with a reason why the IAC would cause the rear cylinder not to fire. I can understand a bad IAC causing the stalling, reving up, then going to a good idle.

What happened with the weak coil output you had in post #1. You must have got that part of it corrected also. That is more in line with having a miss-fire.

But as you said there was alot more done during this repair. Sometimes just a unplug & replug of a connector can fix a problem, especially when you do several at one time.

Great info on that Matco adapter w/ part# for fuel pump pressure testing! Very helpful.
 
I didn't 100% figure out the missfire unless it was a combination of the funky fuel pressure, and computer trying to correct idle. The weak spark just fixed its self. So I am going to guess it was a bad connection on the system. I had the entire harness out of the bike and laying on the floor of the garage when I was testing and inspecting it. I did try a coil off of my friends bike, but it didn't make amy difference.
 
ChadF said:
I didn't 100% figure out the missfire unless it was a combination of the funky fuel pressure, and computer trying to correct idle. The weak spark just fixed its self. So I am going to guess it was a bad connection on the system. I had the entire harness out of the bike and laying on the floor of the garage when I was testing and inspecting it. I did try a coil off of my friends bike, but it didn't make amy difference.
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Good on you, but I hope the electrical Gremlins do not visit you again:s
 
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