Help Vapor lock issue???
Tourer
Joined: May 2010
Posts: 348
Likes: 5
From: The mitten state
IAC= Idle air control motor
MAP= Manifold Absolute Pressure, A sensor that measures the difference between intake pressure and real Baro.
TPS- Throttle position sensor.
I would suspect the PC!
If you are able to have high RPM, it is not vapor lock. Vapor in a fuel injected engine will keep the fuel from flowing through an injector. It might idle rough, but would stall with higher throttle openings.
That said vapor lock is still possible on a system with the fuel pump in the tank. Vapor can form in the supply line to the injector and the injectors themselves can vapor lock. (unlikely but it can happen)
MAP= Manifold Absolute Pressure, A sensor that measures the difference between intake pressure and real Baro.
TPS- Throttle position sensor.
I would suspect the PC!
If you are able to have high RPM, it is not vapor lock. Vapor in a fuel injected engine will keep the fuel from flowing through an injector. It might idle rough, but would stall with higher throttle openings.
That said vapor lock is still possible on a system with the fuel pump in the tank. Vapor can form in the supply line to the injector and the injectors themselves can vapor lock. (unlikely but it can happen)
Advanced
Joined: Mar 2010
Posts: 88
Likes: 0
From: Green Bay, WI
power commander issue. The issue is with the throttle position sensor or TPS. I have seen this many times. IAC is you Idle Air Controller and the map is the predesignated setting for the PC to work off of. HAve the PC reset or remapped. This is assuming you have throttle cables and not electric throttle
Tourer
Joined: May 2010
Posts: 348
Likes: 5
From: The mitten state
Need some help. I have a 2009 Fat Bob. Twice while out on a ride, I have stopped and shut the motor off. It was hard to restart actually had to twist the throttle to get it running then it would not idle on its own. Both times after about a half hour of riding, the problem went away. Both of these episodes were about 2 months apart any ideas or any more info needed
I didn't read this carefully enough! On a FI engine with an IAC ( idle air control) system the IAC motor resets on KEY OFF! It is driven into the "seat" then backed out a "calibrated amount!
When you "twist the throttle to get it started, if you have the throttle open more than a calibrated amount the IDLE AIR control motor is LOST!
It will reset at key off and also during "SOME" driving states. ( it will only reset during a "engine run state" under certain defined conditions.) So the motor will not "always" reset when the engine is running, certain conditions must be met for a "set time" before that will happen.
Many FI engines are harder to start "WARM" than cold. And my Harley ( an 09 )seems also to start hard "warm." This is a function of emissions controls and trying to "START" as lean as possible during a warm restart.
But your lack of IDLE control after you stated it with an OPEN throttle is what can lead to a "LOST" IAC ( idle control motor position!)
Next time it starts hard. Quit cranking , let it sit in th eON position for a second or two and re-press the crank switch. ( without TOUCHING the throttle) If you must "open the throttle", only crack it a "LITTLE BIT" slight twist not too much! A little cracked throttle can be accounted for in the IAC system, but too much throttle at start and YOU will cause the IAC motor to be "LOST". When an IAC motor gets lost it "thinks it is OPEN
( Off the seat further than it might be) so the engine is trying to IDLE with the Motor "actual" position too closed, where the ECM "THINKS" the motor is allowing air that isn't available!!
It was your starting method that most likely caused this problem!
P.S.
I should add here the START UP fuel is a seperate table than the "normal fueling tables" adjusted with a PC. The start up A/F is a function of Temperature. ( IAT/intake air temperature and engine temperature, a stored model value of engine temp
At shutdown vs. TIME) SO start up A/F varies widely between "COLD" and a warm engine! The calibration for start up A/F at whatever the engine /air temperature is after a fill up is on the "too lean side" of the equation! That is why newer Harley engines are hard to start warm!!
Last edited by FBRR; Sep 6, 2011 at 07:19 PM.
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