surging (hunting) idle when cold....

Discussion in 'Gas Engines/Drives/Transmissions/Props' started by CliffA, Feb 1, 2018.

  1. CliffA

    CliffA Well-Known Member GOLD Sponsor

    Dec 29, 2009
    Lake Norman, NC
    2001 Sea Ray 340DA
    Name: 'Happy Place'
    4.5kW West. Generator
    Purchased Nov. 2014
    Fresh Water Use
    Twin Merc. 6.2L (MPI)
    Raw Water Cooled
    V-Drive Transmissions
    long post but I want to give as much detail as possible.....

    I went to my boat yesterday and decided to run my engines for a while...for information it had been several weeks since the last time I ran the engines and we have had sustained and extreme cold temps for this area this winter but my ER temp never got below 40*...

    both engines stared fine without issues and settled into an idle speed around 650 rpms.....

    after a few mins at idle speed both engines stalled at almost the same time....i looked at the temp gauges and they both had reached normal operating temp of 170*F.....it started me thinking that reaching normal operating temp triggered something in the ECM and caused the engines to shut down....

    both engines started back up immediately and settled down once again into a smooth idle of 650 rpms and both were at normal operating temp of 170*....

    when I tied to give the throttle a quick advance bringing the rpms up to around 2,000 and quickly moving the throttle back to idle position both engines would start to surge or 'hunt' for the correct idle by speeding up and slowing down the rpms and after a few seconds of this the engine would stall....both engines exhibited the same behavior.....

    again they both stated back up immediately and would settle into a smooth idle...but every time I tried a quick increase in rpms they both would surge a few seconds and stall....if I did not advance the throttle the engines would idle fine....I could also advance the throttle slowly and both engines would accelerate as expected but once I brought the throttle back to idle position the engines would surge and stall...

    this went on for approximately 15 - 20 mins until I finally decided to take the boat over to a nearby pump out station for a head tank pump out...I traveled at idle speed most of the way since the pump out station is very close...I let the engines idle while I pumped out the head tank without issue....

    on the way back to my slip I blipped the throttle a few times and both engines settled down to a smooth idle without surging or hunting and no stalling....obviously by this time the engines had thoroughly warmed since they had been running for around 45 mins.....

    my first thought is there is a problem with the IAC valve but chances of the IAC failing on both engines at the same time is very remote....

    any suggestions as to the cause of the idle surging and stalling when the throttle is opened quickly and brought back to idle position?

    thanks...

    cliff
     
  2. Little Ducky

    Little Ducky Active Member

    513
    Jun 5, 2017
    Chattanooga TN/Dickson TN
    1998 SeaRay 290 Sundancer
    Twin 5.0L w/Alpha 1 drives
    I'm no mechanic to diagnose so just a question.

    When was the last time you changed the fuel filter and how much fuel was in the tank at the time?

    Could something have settled out and when the engines were started it took a gulp?
     
    Last edited: Feb 1, 2018
  3. JimT

    JimT Active Member SILVER Sponsor

    Jul 7, 2009
    Charlotte, NC- LKN
    2010 330 Sundancer
    T-350mags w/BIIIs & Axius, 5.0 kw Kohler
    Cliff,

    Does not sound like the IAC valves as the engines would stall at low RPM not high with bad IACs.
    Did you treat the fuel?
     
  4. CliffA

    CliffA Well-Known Member GOLD Sponsor

    Dec 29, 2009
    Lake Norman, NC
    2001 Sea Ray 340DA
    Name: 'Happy Place'
    4.5kW West. Generator
    Purchased Nov. 2014
    Fresh Water Use
    Twin Merc. 6.2L (MPI)
    Raw Water Cooled
    V-Drive Transmissions

    thanks for the reply....I change the filters each spring so the last time they were changed was last spring...both tanks have fresh fuel (non-ethanol less than two months old) and both tanks are around 3/4 full....each engine has a separate fuel tank....initially the engines started normally and ran for about 10 - 15 mins at a smooth idle before they stalled so I don't think I have anything blocking the fuel supply....

    cliff
     
  5. CliffA

    CliffA Well-Known Member GOLD Sponsor

    Dec 29, 2009
    Lake Norman, NC
    2001 Sea Ray 340DA
    Name: 'Happy Place'
    4.5kW West. Generator
    Purchased Nov. 2014
    Fresh Water Use
    Twin Merc. 6.2L (MPI)
    Raw Water Cooled
    V-Drive Transmissions

    hey Jim.....I did not treat the fuel but it is less than 2 months old...it is non-ethanol fuel and about 3/4 full in each tank.....I agree that it is unlikely the IAC's gone bad....

    cliff
     
  6. CliffA

    CliffA Well-Known Member GOLD Sponsor

    Dec 29, 2009
    Lake Norman, NC
    2001 Sea Ray 340DA
    Name: 'Happy Place'
    4.5kW West. Generator
    Purchased Nov. 2014
    Fresh Water Use
    Twin Merc. 6.2L (MPI)
    Raw Water Cooled
    V-Drive Transmissions
    I am starting to think I might have water in the fuel, probably from condensation in the fuel tanks from the fluctuations in the ambient temp in the engine room this winter.....

    I have not had problems with water in the fuel before so I am unfamiliar with the symptoms...as I do some research on the internet it appears surging in rpms and stalling are classic symptoms of water in the fuel....

    can anyone that is familiar with how an engine responds to water in the fuel confirm that surging and stalling is indeed one of the symptoms?.....

    this would explain why both engines that are fed fuel from different tanks are demonstrating the same running issues...

    may be time to change the fuel/water separators as Little Ducky suggested....

    thanks...

    cliff
     
    Last edited: Feb 1, 2018
  7. Strecker25

    Strecker25 Well-Known Member SILVER Sponsor

    Nov 20, 2014
    Rochester, NY
    1998 290 Sundancer
    Twin 5.7EFI/Alphas, Kohler 4kw
    we had some wacky behavior with low voltages on the one of our batteries messing with the ecu. I figured the alt would pick up the slack once running but I had to replace the bad battery.

    Did you get a look at the voltages while it was running? Would also be a bit odd for both banks to go at the same time, but just a thought.
     
  8. CliffA

    CliffA Well-Known Member GOLD Sponsor

    Dec 29, 2009
    Lake Norman, NC
    2001 Sea Ray 340DA
    Name: 'Happy Place'
    4.5kW West. Generator
    Purchased Nov. 2014
    Fresh Water Use
    Twin Merc. 6.2L (MPI)
    Raw Water Cooled
    V-Drive Transmissions

    thanks.....all gauges were reading normal when the engines were at idle including the voltage....

    cliff
     
  9. Strecker25

    Strecker25 Well-Known Member SILVER Sponsor

    Nov 20, 2014
    Rochester, NY
    1998 290 Sundancer
    Twin 5.7EFI/Alphas, Kohler 4kw
    You're probably on a better track with the fuel. Is it feasible on the 6.2s to pull the inlet hose from your filter or somewhere near the engine and just pull a pint or so off of each tank? If there's any substantial amount of water you'd be able to tell right away if you put it in a clear container. Our fuel filter inlet is just a flare fitting and relatively easy to get off.
     
    Nehalennia likes this.
  10. CliffA

    CliffA Well-Known Member GOLD Sponsor

    Dec 29, 2009
    Lake Norman, NC
    2001 Sea Ray 340DA
    Name: 'Happy Place'
    4.5kW West. Generator
    Purchased Nov. 2014
    Fresh Water Use
    Twin Merc. 6.2L (MPI)
    Raw Water Cooled
    V-Drive Transmissions

    thanks....I'll have to check on that....

    cliff
     
    Strecker25 likes this.
  11. Nehalennia

    Nehalennia Well-Known Member

    Aug 22, 2007
    Marysville, WA
    2001 310DA twin 350 MAGs, Westerbeke 4.5KW
    Twin 350 MAG V-drives
    I would check fuel first, but the IAC is not out of bounds. They have failed within hours of each other on other boats I know of. Best of luck!
     
  12. GCHOG

    GCHOG Member GOLD Sponsor

    52
    Mar 25, 2016
    Bass River, Viking Marina, South Jersey
    2006 Sea Ray 260 Sundancer
    6.2 Bravo III
    definitely sounds like a fuel problem Cliff. Bad IAC's would not let the engines idle normally. Moisture in the fuel was most likely caused by the fluxuation in temps we've been having lately. You might want to try a few doses of dry-gas first as that is the easiest to start with. Wouldn't worry about the filters just yet. Start out with simple things first.
     
  13. CliffA

    CliffA Well-Known Member GOLD Sponsor

    Dec 29, 2009
    Lake Norman, NC
    2001 Sea Ray 340DA
    Name: 'Happy Place'
    4.5kW West. Generator
    Purchased Nov. 2014
    Fresh Water Use
    Twin Merc. 6.2L (MPI)
    Raw Water Cooled
    V-Drive Transmissions
    thanks.....
    cliff
     
  14. JimG

    JimG Active Member SILVER Sponsor

    Nov 4, 2008
    Southern WV
    2007 310 DA
    Kohler 5ECD
    Twin 350 Mags
    Raw Water Cooled
    V-Drives
    If it's water, the separator filters will be full of water... take them off and dump them into a Mason jar.
     
  15. CliffA

    CliffA Well-Known Member GOLD Sponsor

    Dec 29, 2009
    Lake Norman, NC
    2001 Sea Ray 340DA
    Name: 'Happy Place'
    4.5kW West. Generator
    Purchased Nov. 2014
    Fresh Water Use
    Twin Merc. 6.2L (MPI)
    Raw Water Cooled
    V-Drive Transmissions
    will do...thanks....

    cliff
     
  16. SeadawgVB

    SeadawgVB Member

    97
    Jul 8, 2013
    Tidewater Virginia
    '03 Sundancer 360
    Twin 8.1s with V-drives
    Went to check on my boat a couple weeks back, that I keep in the water all year. It had been really cold (10F) for a few days, so on the first nice warm day I went to check on it, opened the engine hatch and it looked as if it had just stopped raining inside. I had it sealed up to keep the heat from a bilge heater inside (which doesn't help with condensation). Those cold / warm days can probably have the same effect on a fuel tank.
     
  17. Little Ducky

    Little Ducky Active Member

    513
    Jun 5, 2017
    Chattanooga TN/Dickson TN
    1998 SeaRay 290 Sundancer
    Twin 5.0L w/Alpha 1 drives
    As you tinker around, if you have an ah'a moment on why it stalled, please post up.
     
    Last edited: Feb 1, 2018
  18. Espos4

    Espos4 Member

    199
    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS
    Im thinking it’s the fuel too.

    I bought a Crownline 206LS
    2 years ago. It had been winterized and not used for 18 months. Fuel injected 4.3

    It did the same thing. Started and idled fine, but would stall when coming back down to idle speed. Restarted easily each time.

    After filling the tank, it was nearly empty, the engine ran great and didn’t stall anymore. Ran perfect for the 40 hours that i used it that summer.

    Great boat, just too small. Sold it at the end of the 2016 season and bought my current 240 Sundeck.
     
  19. atrick

    atrick Member

    49
    Mar 4, 2017
    Penna
    1995 searay 290 Sundancer
    1990 21 maxum
    Twin 4.3 mercrusers with alpha one drives
    305 chevy with a alpha one drive
    The same thing happened to me and what happened was the air temperature and ER temps were low and the moisture and humidity was high in the ER and there was moisture on the intake around the IAC and with the air moving past the intake it lower the temp of it ice or ice crystals were forming around the IAC causing it to act up. when you cruised over to the pump out station the air temp in the ER went up and the whole engine came up to temp with the moisture level going down from heat of the motors so everything was back to normal. Thats why it happened to both motors at the same time. Just one of those freaks days of just the right moisture and temperature to cause it. Sound far fetched but happens more than you think especially to cars and trucks.
     
  20. BillK2632

    BillK2632 Well-Known Member SILVER Sponsor

    Jun 25, 2009
    Lake Norman, NC
    1999 185 Bowrider,
    Mercruiser 4.3, Alpha I
    Strange, wondering if condensation
    I think this is plausible. A fuel problem is not going to just fix itself after everything gets good and warm. Yesterday was cold high humidity for a winter day. I am guessing the ER was damp. Your really not going to know much until you run it again and see if it happens again. If it happens again I would say pour out the fuel filters into a jar and see what you have.
     

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