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 Post subject: Surging at Idle
PostPosted: Sun Mar 27, 2011 3:20 pm 
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Tadpole

Joined: Sun Mar 27, 2011 3:18 pm
Posts: 2
I have a 1993 Fourwinns 190 horizon with the ford 302 cobra efi/ OMC drive. Boat has been running GREAT. i start hearing a fluctuation in the idle jumping up and down. boat runs smooth at higher RPMS but at idle it surges up and down gradually surging higher and higher and eventually smoothing out for a moment and then surges again. i've tried the MAP sensor, IAC valve, TPS sensor, replacing the battery, cleaned the air filter, replaced the anti syphon valve not long ago, sprayed out the throttle body, fuel pump pressure is at 30 something psi. i haven't been able to find a vacum leak but i'm still looking. i'm so confused because it runs great at anything other than idle. any suggestions would be appreciated. thanks.

my next thought was possible the alternator? the electrical system isn't getting enough voltage? i looked at the gauge and its reading just above 12-13.

any input or suggestions would be appreciated


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 Post subject: Re: Surging at Idle
PostPosted: Sun Mar 27, 2011 4:29 pm 
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Joined: Mon Oct 27, 2008 7:13 pm
Posts: 1303
Location: Allatoona Lake, Georgia
My port engine had a bad fuel pump last year and it did the surging and sputtering bit too.

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Current Boat: 2000 Four Winns 298 Vista
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 Post subject: Re: Surging at Idle
PostPosted: Sun Mar 27, 2011 9:50 pm 
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Villiage Idiot

Joined: Sat Dec 15, 2007 8:28 pm
Posts: 1405
Location: Kansas City
Looks like you checked the main culprits. Given your boats age is about 8 years, try changing the plugs, wires and cap/rotor (I assume you did the fuel filter). Had a 5.0L Mustang do as you described, due to plugs getting fouled a bit at idle. Would clear once I got some air-flow through the engine, but would get a little blocked up at idle (I could lean out the fuel to each cylinder until it would clear up with a hand-held computer).

As far as a fuel press issue, could still be (stay constant?). Pull the vac line from the fuel press regulator and see if it does the same. Try running it with your fuel cap off too.
Try an actual Volt meter, and make sure the voltage regulator is OK on the alt. I think you should normally see about 14V with a properly running alt. Maybe hook up a batt charger (10A should be plenty) and see if that makes it stop surging.

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Black '07 H210SS
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