View Full Version : RPMs go up when shifting
06-04-2005, 11:36 AM
'02 X-7 with 310Hp.Indmar
Can anyone tell me if there is some electronic control over the idle rpm that would slightly speed up the RPM (from 640 to @820) when I begin to move the gear shift level from neutral toward forward or reverse? There is no throttle linkage moving & yet the RPM's go up, and after 5 to 8 seconds drifts back down to the 640. I don't want to engage at the higher RPM so I always have to wait. What controls this?
(A new ECM was installed under warranty last fall & it started right after that) Paul Greensboro, NC
What is the status of your Perfect Pass(or equivalent)? It sounds like the IAC either needs to be reset or the ECM thinks there's a need for more RPM. What other info can you provide here? Why was the ECM replaced and how long id it take the dealer to replace it? Did they reprogram(update) it, too?
06-05-2005, 05:39 PM
Hi Jim: The ECM was replaced under warranty last fall. The boat was at the dealership for almost 4 weeks. It simply ran fine the time before, but the next time I went to use the boat it would not start. Took to dealer & they said the engine code Calibration check Sum Failure that would not clear meant the ECM was toast. They said it had 7 to 8 codes stored that would not clear. Replaced ECM.
As far as current scenario: I think the RPM speeds up even with the perfect pass off. It does not seem to be Perfect pass related since I feel no movement of the throttle cable when someone moves the shift from neutral & starts the transition to forward. I am not sure about the ECM update or reprogram. The dealer was dealing w/ someone from Indmar named Joe Cutlery? who forwarded the ECM after warranty was established. Any help will be appreciated. Thanks. Paul Sheehy
If the PP was acting up, you wouldn't feel the throttle move, the cable is moved by he PP servo independently. You can check it visually, though. Just open the motor box and have someone shift to forward and see if the PP moves the cable. If the RPM increases with the PP off, it sounds like the IAC follower and IAC may need to be reparked. The ECM wants to see a certain speed for idle and controls the IAC to get it, but the ECM doesn't actually know where the IAC is. It just tells it where to go, based on the program.
Just for grins, disconnect the throttle position sensor and see if the problem goes away.
Is the problem the same when the motor is cold and hot?
06-06-2005, 11:20 PM
Thanks Jim, but I need some additional explanation. I did ck the Perfect Pass for movement when someone else ease the shift out of neutral. The RPMs immediately come up (@ +200) but the servo did not move or did I feel any throttle cable movement at the engine cable bracket. I don't know what you mean regarding the IAC follower & the IAC may need to be re-parked. Can you please explain? Where is the throttle position sensor so I can disconnect it to see if that changes anything? Yes the problem is the same regardless if the engine is hot or cold. It always increases RPM immediately after leaving the straight up neutral position, but before it goes into gear. If I hesitate & wait a moment before proceeding forward with the shift lever to engage gear, it will drift back down to the proper 620- 640 rpm. At that point I shift into gear. Thanks for your help. Paul Sheehy
Actually, I meant throttle follower.
The IAC(Idle Air Control Motor) is for achieving and maintaining the correct idle RPM and is basically a vacuum leak controlled by the ECM.
The throttle follower means that the IAC follows the throttle movements through acceleration/deceleration by opening and closing when necessary and prevents bogging. Reparking means that the ECM closes the IAC completely, (the IAC is also called a stepper motor which basically moves in discreet increments, or steps) and opens it to a predetermined point.
If you look at the throttle plate, on one side you will see a sensor with three wires attached to it, Blue, Grey and Black. Bend the retainer slightly and slide it off. You may see the engine light go on while the plug is removed but that will go away when it's reconnected.
06-12-2005, 08:55 PM
JimN: To "park" the IAC- should I start the engine 1st, then unplug the IAC, then plug it in or do I unplug, turn the key on, then plug back in, or what? What is the correct sequence? Paul Greensboro, NC
That won't do it. As far as I know, it should only be done through the ECM. Manually moving the pintle isn't recommended. Remove the flame arrestor and look into the throttle body where the idle air goes in. This is at the end of the IAC and you will see a cone shaped part that moves when the throttle is moved with the motor running. Turn the key off and look at it- it should close slowly after the key is off. When the key is turned on again, it should open a bit. If it doesn't fully close, it needs to be reset.