Surging idle 6.2 mpi

[dane174]

I need help
My 2001 260 Sea Ray Sundancer with 6.2 liter MPI and 300 hours surges at idle in neutral from 600 rpms to 1200rpms repeating about every 4 seconds until it dies. It will idle all day in gear but as I am bumping in and out of gear to dock it the problem begins. If I turn the ignition off and restart, the problem goes away long enough to dock. If I restart without turning off the ignition it continues to surge. This surging happened only intermittantly when I bought the boat two years ago but is happening more frequently so I brought it into a reputable marine repair shop to do a computer diagnogstic check. They have replicated the problem but no computer codes or sensor problems are showing up and their mechanic is stumped. He is checking with other mercruiser techs but after two weeks still no solutions. Has anyone had this problem or have any ideas as to what might cause it? I would appreciate any input. Thanks
Dane174

 

[CliffA]

I need help
My 2001 260 Sea Ray Sundancer with 6.2 liter MPI and 300 hours surges at idle in neutral from 600 rpms to 1200rpms repeating about every 4 seconds until it dies. It will idle all day in gear but as I am bumping in and out of gear to dock it the problem begins. If I turn the ignition off and restart, the problem goes away long enough to dock. If I restart without turning off the ignition it continues to surge. This surging happened only intermittantly when I bought the boat two years ago but is happening more frequently so I brought it into a reputable marine repair shop to do a computer diagnogstic check. They have replicated the problem but no computer codes or sensor problems are showing up and their mechanic is stumped. He is checking with other mercruiser techs but after two weeks still no solutions. Has anyone had this problem or have any ideas as to what might cause it? I would appreciate any input. Thanks
Dane174

my starboard 6.2 was doing this last year so I decided to do a full tune-up on both engines which included:
- spark plugs
- spark plug wires
- distributor cap
- distributor rotor button
- distributor ignition sensor
- IAC (idle air control) valve
- fuel/water separator filter
- flame arrestor cleaning

it was time for an engine tune-up anyway.....there were no fault codes stored in the ECM.....whatever was causing this problem did not throw a fault code....

the good news is the surging problem was gone afterwards....the bad news is I don't know exactly which item was the fix....:huh:....my first guess would be the IAC valve.....

cliff

 

[dane174]

my starboard 6.2 was doing this last year so I decided to do a full tune-up on both engines which included:
- spark plugs
- spark plug wires
- distributor cap
- distributor rotor button
- distributor ignition sensor
- IAC (idle air control) valve
- fuel/water separator filter
- flame arrestor cleaning

it was time for an engine tune-up anyway.....there were no fault codes stored in the ECM.....whatever was causing this problem did not throw a fault code....

the good news is the surging problem was gone afterwards....the bad news is I don't know exactly which item was the fix....:huh:....my first guess would be the IAC valve.....

cliff

Thanks Cliff I was thinking the same thing about the IAC but the mechanic said he checked that. Still waiting to hear from a regional tech and hope I get the boat back before winter comes here in Duluth, mn.

 

[CliffA]

Thanks Cliff I was thinking the same thing about the IAC but the mechanic said he checked that. Still waiting to hear from a regional tech and hope I get the boat back before winter comes here in Duluth, mn.

IAC valves are pretty cheap and you should keep a spare on hand anyways.....you might want to buy a new one just to try it out and if that does not fix the problem at least you have a known good spare.....

cliff

 

[370Dancer]

Turning the ignition off and back on primes the fuel pump. Only thing on your list was the separator. The symptom sounds like fuel starvation.

 

[CliffA]

Turning the ignition off and back on primes the fuel pump. Only thing on your list was the separator. The symptom sounds like fuel starvation.

it certainly could be fuel starvation.....but it could also be ignition related....that is actually the first thing that needs to be determined before getting too deep....is it a fuel issue or is it an ignition issue?.....the list of things I did to solve my problems dealt with the possibility the issue is ignition related.....there is a whole other list of things to check if the issues turns out to be fuel related....

cliff

 

[coreyf311]

I second the IAC. My 350 mags also have an IAC "muffler" that needs to be changed periodically. Just a foam square in the throttle body the acts like an air filter for the IAC. I had similar issues and both filters where black. Changed them out on both motors. Now the idle perfectly. Costs like 2 dollars.


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[scoflaw]

The curve ball with the OP's problem is that his engine idles all day in gear.