8.1L Stall on Throttle Down

[Teakind]

I'm hoping someone might have had a similar experience with their Engine as I am having and I couldn't find a thread to address the issue.

I have an 8.1L Engine in a 2001 230VRS. I bought it last year used and it has been maintained by a dealer always - never left the marina. The boat had about 300 hours on it when I bought it.

It has always run great. I have kept the fluids fresh and changed air filters, etc. Everything seems almost new with the boat except for one item.

When I pull off of a cruise (any planing speed), as in a wake boarder, skier, etc, needing to be picked up, the engine will stall every time unless I drag out the decel down un-reasonably slowly. The engine always runs great at idle other than when I back off the throttle. Once stalled, the engine starts up immediately and performs perfectly again. It is difficult to operate it so that it does not stall in those cases.

Any thoughts or similar experiences?

Thanks

[JimN]

I'm hoping someone might have had a similar experience with their Engine as I am having and I couldn't find a thread to address the issue.

I have an 8.1L Engine in a 2001 230VRS. I bought it last year used and it has been maintained by a dealer always - never left the marina. The boat had about 300 hours on it when I bought it.

It has always run great. I have kept the fluids fresh and changed air filters, etc. Everything seems almost new with the boat except for one item.

When I pull off of a cruise (any planing speed), as in a wake boarder, skier, etc, needing to be picked up, the engine will stall every time unless I drag out the decel down un-reasonably slowly. The engine always runs great at idle other than when I back off the throttle. Once stalled, the engine starts up immediately and performs perfectly again. It is difficult to operate it so that it does not stall in those cases.

Any thoughts or similar experiences?

Thanks

Look into the IAC (Idle Air Control) motor- it's located on the throttle body and has a four wire harness connected to it, with a green pair & blue pair. One of each pair has a black tracer line and the other has a white tracer. It's not a part that will cause a code to be stored or displayed, but it can mess up the way it runs on acceleration/deceleration.

You should be able to see the tip (called the 'pintel') move when you turn the key to ON and OFF. If it doesn't move sufficiently/properly, it will stall. It's supposed to close when the key is turned to OFF, then re-open a specific amount. You should also be able to see it while the engine runs- on hard acceleration, it should open and on hard deceleration, it should close until the engine RPM approaches idle (650 RPM), at which time it should start to re-open and allow it to idle normally or reach the desired RPM. If it's not moving at all, unplug the harness and use a multi-meter (set for DC Volts) to measure voltage on each pair- one pair will show + Voltage when the key is turned to ON and the other pair will show + Voltage when the key goes from ON to OFF. If you don't see this voltage, start the engine and check for voltage on hard acceleration & deceleration- if you still don't see any Voltage, it might be the ECM's IAC driver circuit. The ECM can be tested for this, but it would have to be tested with a diagnostic computer (this can function the IAC) or sent in to MC, Indmar or someone else who can determine the problem.

[Cumminscj]

Jim: will the iac function or move at all if the throttle doesn't return to the idle position of less than 2%?

[mikeg205]

is the throttle body clean? if not the engine may be getting oxygen starved - any codes?

'01 should be able to test for trouble codes with out a special device - ECU not MEFI5

[lj_mastercraft]

I will throw in that in every 8.1 I've ever ridden in, mine included, a high throttle and quick 'neutral' pull, there's a good chance the engine dies. I always bring mine down (~2-3 seconds) from heavy throttle to neutral to avoid it stalling