Another Magneti Marelli post
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Intermediate
Joined: Apr 2018
Posts: 29
Likes: 1
From: Homosassa
Another Magneti Marelli post
All,
First, I have no intention of changing this old EFI to carb. I've done that on other bikes, and the cost doesn't seem to warrant the outcome.
I did some preventive maintenance on the bike because it's old, like me, and I use it to blast down the highway a lot. It's a 1998 FLHPI Road King with 9K miles on it.
I had some intermittent, (not bad) idle issues with it, and when it was hit in a parking lot, I took the tank out to be repainted and replaced the fuel pump, fuel filter and the idle air control module. I started it for the first time last night, and it shot up to 3k rpm and would not come down. The new module is an aftermarket one from Ebay, but they all look identical except the tip was different than the OEM one so I exchanged the new one with the old one so it would fit on my bike. Where should I look to adjust this? I've looked at a couple of videos on YouTube, but the bike did not have any acute idle problems before I messed with this module and don't want to chase it by messing with the sealed adjustment screws on the throttle body. I hope it is something simple I can start with without replacing a bunch of sensors that worked fine before. Thanks!
First, I have no intention of changing this old EFI to carb. I've done that on other bikes, and the cost doesn't seem to warrant the outcome.
I did some preventive maintenance on the bike because it's old, like me, and I use it to blast down the highway a lot. It's a 1998 FLHPI Road King with 9K miles on it.
I had some intermittent, (not bad) idle issues with it, and when it was hit in a parking lot, I took the tank out to be repainted and replaced the fuel pump, fuel filter and the idle air control module. I started it for the first time last night, and it shot up to 3k rpm and would not come down. The new module is an aftermarket one from Ebay, but they all look identical except the tip was different than the OEM one so I exchanged the new one with the old one so it would fit on my bike. Where should I look to adjust this? I've looked at a couple of videos on YouTube, but the bike did not have any acute idle problems before I messed with this module and don't want to chase it by messing with the sealed adjustment screws on the throttle body. I hope it is something simple I can start with without replacing a bunch of sensors that worked fine before. Thanks!
Last edited by CIC2016; Aug 27, 2023 at 06:17 AM.
Grand HDF Member
Joined: Jul 2007
Posts: 3,736
Likes: 8,516
From: Bates County MO
Cycle the ignition switch a few times to let the system learn where "0" throttle position is, observing the IAC motor and the throttle blade to see if it's closing properly. The new idle air controller may be holding the throttle blade slightly more open than expected, elevating the idle. Pull the air cleaner, start the bike, and pinch the nostrils (idle air passage on the upper inside of each tube of the throttle body). If it continues to run, then you have air leaks- either the throttle blade isn't seating properly, or faulty intake seals, or both. Adjust/correct the throttle stop screw & the idle speed screw. If it does die, It's possible the engine temp sensor ( top center of the front head, 32446-95A) is failing, which will raise the engine idle speed due to an extra amount of fuel available at idle.
This may help.
This may help.
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,079
Likes: 2,151
From: Ohio
M&M doesn't use a IAC but has a flow sensor and electric stepper motor for fast idle, going to assume your messing with the stepper motor. The fast idle stepper motor has a screw setting it while the engine is cold, when you key on it should activate moving out and moving back in stopping according to the engine temperature.
The wildcard, stepper motor position and idle fuel mixture is controlled by the ECM signaled from the engine temperature sensor. The ETS is the heart of the M&M system and usually the failure of the system. Good plan of attack is to back the stepper motor off disabling it and ride the bike seeing if the idle condition without it is gone, we are eliminating fast idle control and checking ETS because it has the ability to change idle by fuel mixture. If rideability idle is ok, set the stepper motor fast idle cold to proper rpm, pull the ECM fuse for 5 minutes resetting it so it can relearn, if it returns the stepper motor is bad.
Keep in mind the M&M isn't a smart system and very rarely detects the ETS failure, the sensor is just a ghost that can mess with the system
The wildcard, stepper motor position and idle fuel mixture is controlled by the ECM signaled from the engine temperature sensor. The ETS is the heart of the M&M system and usually the failure of the system. Good plan of attack is to back the stepper motor off disabling it and ride the bike seeing if the idle condition without it is gone, we are eliminating fast idle control and checking ETS because it has the ability to change idle by fuel mixture. If rideability idle is ok, set the stepper motor fast idle cold to proper rpm, pull the ECM fuse for 5 minutes resetting it so it can relearn, if it returns the stepper motor is bad.
Keep in mind the M&M isn't a smart system and very rarely detects the ETS failure, the sensor is just a ghost that can mess with the system
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