350 MAG MPI high idle and suction noisie

[achris]

.... meaning if I’m standing inside the boat looking backwards at the engine the hoses to the vent and fuel regulator are on the left side and the pvc hose goes to the right when standing inside the boat looking aft at the engine

Now my head is spinning just trying to understand what you saying. The port side of the engine is on the port side of the boat (the one that has the red nav light on it), regardless of which way you're looking, or even if you're standing on your head.

PCV valve should be in the port valve cover. If it's in the starboard cover, then the hose is reaching all the way around the throttle body, yes?

This is a 'Ski' engine, so do you have a V-drive, meaning the front of the engine is facing the back of the boat?

Chris......

 

[stillcantfly]

yes this is a ski engine. Vdrive.... sorry I understand now front of the engine is all the belts then yes the pvc and and everything else is hooked up correctly

 

[stillcantfly]

[No message]

 

[stillcantfly]

[No message]

 

[stillcantfly]

[No message]

 

[stillcantfly]

[No message]

 

[stillcantfly]

as you can see from the pictures the PVC and other lines are disconnected from the TB so I can remove the TB and show you the bottom of the plate I don't understand how the gaskets work it covers the center port but has a hole and goes nowhere. the outside ports go into the bottom of the TB through the vents created

 

[alldodge]

What connects to this line and does it have a port which connects to the IAC chamber

Edit: That may just be the TPS connector

I'm looking for how air gets to the IAC

 

[stillcantfly]

That doesn’t have a port but it connects to the throttle position sensor

 

[stillcantfly]

Sorry it is the throttle position sensor that’s where the wire from the harness connects

 

[alldodge]

OK
How does the IAC get air so it can open and allow that into the TB?

 

[stillcantfly]

From the top of the throttle body looking down there is a little inlet that the suction noise is coming from which goes into the middle port on the bottom. The TPS is just mounted onto the TB doesn’t have anything going into the TB. The IAC gets air from the center port on the bottom of the TB where the suction noise is coming from looking from the top down And It has it’s own port on the bottom that it extends and retracts a plunger in and out of a hole that connects the two ports

 

[alldodge]

The hole on the middle should be the air intake for the IAC if it is above the throttle plate. The throttle plate is adjusted so the IAC will be about 40 counts at idle. If there is to much gap in the plate then the idle is higher. The O-ring on the IAC is critical for idle.

Is the O ring in place?
Is the surface area where the IAC pintle seats in the TB clean and smooth?
When the IAC is placed into position, does the pintle tip make contact before the main body does? Trying to see if there is any pressure from the tip to close to air port off

 

[stillcantfly]

amazing job with the pictures and adding notes helped understand how how it works the o-ring is in there and new. I don't see anything blocking the hole the pentle goes into. its seems smooth to me. the center ports hole is above the TB plate.the only thing is how does the air let work on the TB? the reason I ask is yes there is a hole in the gasket but if you look at the plate the TB bolts onto there is not a hole so only the gasket has a hole? also the pintle doesn't touch the hole when installed.

 

[alldodge]

Good point
There is 2 TB which are similar, one with I/O and one like yours with IB. The I/O has a different lower and different gasket. The hole I'm pointing out does nothing in your case. Air comes in thru the slot, and passes by the IAC and out thru the opening cut out in the gasket.

The PVC just uses a slot to create a source for vacuum

It has got to be a vacuum leak.

The leak is caused by a IAC which is not working correctly (bad part) or not being controlled correctly (issue with ECM)

The leak can also be caused by crack or gap in the intake or bad gasket.

The IAC can be unplugged and there is no change, so the IAC is not working.
If all ports are plugged the motor dies, so this also states the IAC is not working and just stays closed.

Need to scan the motor and see what the IAC count is while idling.

If there is no codes, and IAC is at or near zero then we might be able to say the ECM is working, but not 100%.

Place a Tee fitting between PVC and TB. This will allow the PVC to work as it should, but will not reduce/increase the vacuum number

 

[stillcantfly]

What does putting a T in between the pvc and the TB do? Also thank you so much for helping me means a lot. Where else can I check for a vacuum leak? I’ve checked the line between the pvc and TB nothing then from TB to pressure regulator nothing I’m stumped. Is there any other vacuum I’m missing?

 

[alldodge]

The last thing I remember ( I'm old and forgetful) that the PVC was disconnected and a vacuum gauge was used in its place. Doing it this way, stops all the slight leaking (PVC does leak small amount of air past, this is as designed) and the gauge will read the vacuum at the intake. This reading without the PVC in place will be higher then with it installed.

Previous reading was close to 15 Hg

Adding a Tee in line with the PVC will give what the motor is actually drawing with all components connected

What was it when you connected it to the fuel pressure regulator?

 

[stillcantfly]

I haven’t tested that one yet but will do in the morning and post results

 

[stillcantfly]

Ok tested with a T valve installed the hg is still 15 on the pvc line running fuel regulator test side now

 

[stillcantfly]

Ok tested with a T valve installed the hg is still 15 on the pvc line running fuel regulator test it’s also pulling 15hg pictures to come