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2002 380 DA touchy throttle- can it be an adjustment?

 
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Pseudomind



Joined: 23 Jun 2009
Posts: 11
Location: Jacksonville, fl

PostPosted: Mon Oct 11, 2010 7:36 am    Post subject: 2002 380 DA touchy throttle- can it be an adjustment? Reply with quote

V-Drives

For the most part my throttles wild synch fairly close, bu twhem I am down under 2000 RPM between 2000 and 1000 rpm's th eport side will act very squirrel y by just barely moving it and drop down anywhere from 300 - 6oo rpm different, in fact the synch gauge port side will drop all the way down to the left side of the gauge.

Think of it this way the way when docking by using the shifters how you turn the boat.

Now hold that thought.

Let's say you are entering a no wake zone, and start slowly throttling back both throttles together. When suddenly the port drops off by 300-600 RPM. Now the boat wants to try and steer to port.

I have to try and play with port throttle to get back to synch, I will barely touch the port throttle (up?forward) it seems and it will shoot up the synch gauge past the center synch mark over to starboard and yes the boat reacts by now wanting to turn to starboard.

I guess what I have is a very touchy throttle reaction on the port side, but I have no idea what to look at in order to fix/correct.

Any ideas?

Thanks
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MikeW
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Joined: 01 May 2006
Posts: 680

PostPosted: Mon Oct 11, 2010 10:29 am    Post subject: Reply with quote

Hello, what is the engine serial number? Lets take a look at the fuel system. Cool
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Pseudomind



Joined: 23 Jun 2009
Posts: 11
Location: Jacksonville, fl

PostPosted: Mon Oct 11, 2010 10:39 am    Post subject: Reply with quote

Fuel Injected

Port Engine Mercruiser T8.1S OM313118
Starboard Engine Mercruiser T8.1S OM312579
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MikeW
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Joined: 01 May 2006
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PostPosted: Mon Oct 11, 2010 10:59 am    Post subject: Reply with quote

It sounds like you are having trouble with the (IAC) idle air control motor. Cool
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Pseudomind



Joined: 23 Jun 2009
Posts: 11
Location: Jacksonville, fl

PostPosted: Mon Oct 11, 2010 11:21 am    Post subject: Reply with quote

MikeW wrote:
It sounds like you are having trouble with the (IAC) idle air control motor. Cool


Could I trouble you to possibly provide me with a bit more detail about this, and what might be happening?

Thanks
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Pseudomind
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MikeW
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PostPosted: Mon Oct 11, 2010 11:37 am    Post subject: Reply with quote

Here is a link to look at. Cool
http://www.2carpros.com/topics/iacvalve.htm
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Pseudomind



Joined: 23 Jun 2009
Posts: 11
Location: Jacksonville, fl

PostPosted: Fri Oct 15, 2010 9:16 am    Post subject: Reply with quote

t idles just fine, basically operates just fine, except around or above 11600-2000 rpms on the port and starboard engines. The Throttle position sensor's check out okay with Mercrusier scanner software, Mercrusier suggested possibly a plug issue, so plugs were changed, Old plugs were basically still good now Mercrusier suggests sending in the ECM's to be flash updated.

Addendum, Mercruiser does not now believe it could be the ECM's they cannot be flashed anyway according to them, but just replaced. Now they think it may be a coil for plug wires, each wire has a coil so each must be checked
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MikeW
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PostPosted: Fri Oct 15, 2010 10:24 am    Post subject: Reply with quote

An ignition problemshould show up on the computer. Have the engine scoped. Cool
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Pseudomind



Joined: 23 Jun 2009
Posts: 11
Location: Jacksonville, fl

PostPosted: Wed Dec 08, 2010 7:48 am    Post subject: Reply with quote

Note; this issue is with both engines and encompasses about a 300 RPM sudden range change, and only happens under 2000 RPM. It is not just a tachometer display change but also a noticeable engine change in RPM.

Port typical will jump down to about 1300 RPM's when when you approach 1600 RPMs

Starboard typical will jump down to about 1600 RPM's when when you approach 1900 RPMs

Engined tested with another ECM, Plugs all changed both engines, Throttle position sensor changed idle Air Control changed, throttle body cleaned, Injector cleaner, (Quick Clean added)

I have always used Startron and Valtech fuel, no ethanol.

Mercruiser has no idea of the cause, mechanic of some years who works here at the yacht center has never encountered this situation. This yacht center does major repairs.
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Pseudomind



Joined: 23 Jun 2009
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Location: Jacksonville, fl

PostPosted: Mon Jul 25, 2011 4:34 pm    Post subject: Reply with quote

I finally found the issue. It was the starboard prop.
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