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Solved:I'm Stumped, sputter, high idle


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Well at first I thought I had bad gas, engine would sputter at mid RPMs after really warmed up, after that, it would sputter at low RPMs, but would run WOT just fine.  Two tanks later and several bottles of Heat, convinced its not the gas.  I then thought it was the ICM (ignition control module), since the symptoms were similar to an issue 4 years ago.  Well that is not is either.

Sometimes it idles at 1200 rpm, other times normal, runs normal, but after a while will sputter at mid and low RPMs.

Any clue?  I'm thinking fuel injectors now, but the way it sputters, seems like more than one, at low RPMS sputter so bad comes close to stalling, (but hasn't yet)

Also tried a can of seafoam.

 

Edited by iliketoski
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yes, sure did, but the new one is acting same as old, and the high idle started again 5 min after starting the engine.

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electricjohn

No vacuum leaks? Everything tight? Plenum, throttle body, ect ? My next guess would be coil. 

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Posted (edited)
1 hour ago, justgary said:

Recent tune up?  Plugs, cap, and rotor?  Plug wires ever changed?

New plugs every other year, new cap, rotor and wires within 3 years.  (I'm pretty good on PM).  Also new fuel filters (2) every year.   Fuel pump was about 4 or 5 years ago 

Edited by iliketoski
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1 hour ago, electricjohn said:

No vacuum leaks? Everything tight? Plenum, throttle body, ect ? My next guess would be coil. 

Nothing obvious on vacuum leaks, (visual check).  I thought of the coil, but the high RPMS at idle made me second guess that, actually made me second guess even trying the ICM.

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Spray some starting fluid around the throttle body and intake manifold to see if you have a leak.  You should get a good bump in RPM when you find one.

Clean the inside of the throttle body, including the edges of the butterfly and in the side passages.

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Posted (edited)
33 minutes ago, justgary said:

Spray some starting fluid around the throttle body and intake manifold to see if you have a leak.  You should get a good bump in RPM when you find one.

Clean the inside of the throttle body, including the edges of the butterfly and in the side passages.

Gary,   Thanks for the input, but suddenly a leak in the throttle body/manifold?  Seems more mechanical than that.

Edited by iliketoski
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1 hour ago, iliketoski said:

Gary,   Thanks for the input, but suddenly a leak in the throttle body/manifold?  Seems more mechanical than that.

I'm just trying to help... we can cut bait or we can fish.  You came here with a problem.  It is hard to rule out what might be wrong until you determine that it isn't wrong.  Eventually you can discover what was wrong if you rule out the good. 

You did a visual check for leaks, so you must have thought it was possible.  An o-ring can crack on an injector or TPS or IAC and give you a leak.  I told you a definitive test for intake leaks.  Don't do it if you don't want to. 

Cleaning the throttle body will ensure that you don't have carbon buildup in the butterfly edges or in the IAC.  Don't do it if you don't want to.

Chasing a problem that could be caused by gunk before you clean out the gunk could lead to a long diagnosis and a lot of wasted parts.

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Thanks Gary,

I was just thinking that since the problem happened all of a sudden, it seemed like something "broke".  I will definitely try testing for the leak,   The throttle body cleaning seems like it would be a progressive problem.  Again, not doubting, just talking through realism.
 

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Posted (edited)

Sleeping on this and the vacuum leak suggestion, would a failed PVC cause this, I don't think it has ever been replaced?  It seems like you have to remove the fuel rails to get to it.  How are they attached?  Or is there a simpler way?  Also where are all the vacuum lines I only see a total of 3 vacuum lines.

 

Since the PVC is difficult to get to, do you think you could just squirt some carb cleaner in it to clear it.  The symptoms are intermittent, so maybe it gets stuck every so often, and WOT makes it open temporarily?

Edited by iliketoski
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fuel rails are easy to remove.  Four allen head bolts and lift straight up.  Don't drop the spacers between the rails and the bosses or you'll spend hours looking for them.  Ask me how I know.

Have you checked your fuel pressure?

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19 hours ago, iliketoski said:

New plugs every other year, new cap, rotor and wires within 3 years.  (I'm pretty good on PM).  Also new fuel filters (2) every year.   Fuel pump was about 4 or 5 years ago 

So... did you actually pull the cap and look at it, or just decide that it was "new enough" that it couldn't be the problem?

It seems like you prefer to prognosticate over potential causes rather than diagnosing them.  I suppose I understand, but at some point you probably will have to check some of the things we have mentioned in order to actually get the engine running correctly again.

Given that you never even told us which engine you have, I find it hard to continue.  It would be great if you told us everything you have done or changed on the engine *recently* and whether your issue slowly came around or popped up all of a sudden.

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Posted (edited)
10 hours ago, UWSkier said:

fuel rails are easy to remove.  Four allen head bolts and lift straight up.  Don't drop the spacers between the rails and the bosses or you'll spend hours looking for them.  Ask me how I know.

Have you checked your fuel pressure?

I have not checked fuel pressure, don't have the gauge at the lake.   I wouldn't think the high idle would be a symptom of pressure.

Where are the allen screws located?  I don't see them, underneath?

 

PVC valve look like an option?   Do you think some carb cleaner will be OK temporarily?

Edited by iliketoski
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9 hours ago, justgary said:

So... did you actually pull the cap and look at it, or just decide that it was "new enough" that it couldn't be the problem?

It seems like you prefer to prognosticate over potential causes rather than diagnosing them.  I suppose I understand, but at some point you probably will have to check some of the things we have mentioned in order to actually get the engine running correctly again.

Given that you never even told us which engine you have, I find it hard to continue.  It would be great if you told us everything you have done or changed on the engine *recently* and whether your issue slowly came around or popped up all of a sudden.

You've been a great resource over the years, now just an being an a**

Its a monsoon 330, which I thought you'd know from my signature. sorry for the assumption.

When I pulled the cap to change the ICM it looked pristine, no, corrosion, still looks brand new

Its great to capture all ideas, but honestly some need to be challenged with additional info that might eliminate them.  I do new plugs every other year.  Cap, rotor and wires ~ 3 years, several tanks of different gas, several bottles of heet, 1 can of of Seafoam, new ICM, checked for apparent vacuum leaks, (on the 3 lines I could find, puller hose off PCV valve (RPMS increased), replaced vacuum hose, but wondering if valve could be malfunctioning..

It started by sputtering at mid RPMs. after backing off continues at Idle RPMs, after heet and seafoam, thought cured, but reappearred, then also started doing high idle RPMs, (no sputtering).  Comes and goes, sometimes runs fine, other time high idle, then perfect.   

 

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I had a similar problem a few years ago.  thought fuel and filters and ended up a new set of plug wires solved it. 

And they were prettier than the old ones - win-win.

 

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9 hours ago, Soon2BV said:

I had a similar problem a few years ago.  thought fuel and filters and ended up a new set of plug wires solved it. 

And they were prettier than the old ones - win-win.

 

Yea, I have to agree, new plug wires sure dressed things up, mine are bright blue.

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16 hours ago, iliketoski said:

You've been a great resource over the years, now just an being an a**

Its a monsoon 330, which I thought you'd know from my signature. sorry for the assumption.

When I pulled the cap to change the ICM it looked pristine, no, corrosion, still looks brand new

Its great to capture all ideas, but honestly some need to be challenged with additional info that might eliminate them.  I do new plugs every other year.  Cap, rotor and wires ~ 3 years, several tanks of different gas, several bottles of heet, 1 can of of Seafoam, new ICM, checked for apparent vacuum leaks, (on the 3 lines I could find, puller hose off PCV valve (RPMS increased), replaced vacuum hose, but wondering if valve could be malfunctioning..

It started by sputtering at mid RPMs. after backing off continues at Idle RPMs, after heet and seafoam, thought cured, but reappearred, then also started doing high idle RPMs, (no sputtering).  Comes and goes, sometimes runs fine, other time high idle, then perfect.   

 

Your signature doesn’t appear when viewed with a mobile browser.  I can see the boat description on your profile but not on the thread when viewing from an iPhone.  As Rod Tidwell so aptly put it, “Help me help you Jerry.”

 I understand your frustration but put me down as one who genuinely appreciates input from those on this forum willing to chime in and make suggestions. Without this help I would have gone broke or sold my boat after the first summer more than ten years ago.

 

Edited by Bozboat
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Although the symptoms sounds like some component malfunction, think about what you did just prior to the event in question.  Many times it boils down to human intervention being the root cause.

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Thanks for ALL the suggestions, I'll keep you posted

2 hours ago, Woodski said:

Although the symptoms sounds like some component malfunction, think about what you did just prior to the event in question.  Many times it boils down to human intervention being the root cause.

I have to say I literally did nothing from when it worked until the problem arising, it worked one weekend then not the next, (except put gas in it, and I've tried bottles of HEET and ran through some different fuel sources that hopefully eliminated this possibility.    That's not to say I haven't caused problems in the past :-). 

 

Will check out the diagnostic guide!

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Do you have the old style kill switch with the plastic clip that holds the red button in?  When the plastic clip gets old and weak, the red button will move causing the engine to cut on and off. The newer style is a a better designed clip that holds the red button out.  

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I do have the old style, I'll have to jumper it out of the situation.  (I've never had the clip off in 20 years :-)

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  • 3 weeks later...

Just to update:

I took it into the dealer 2.5 weeks ago, they are stumped and working with Indmar:

So far they have tried/tested

  • Fuel pressure
  • New Cap
  • Another new ICM
  • Checked timing
  • Replaced IAC valve
  • Replaced distributor
  • Shared all engine readouts w/Indmar
  • Checked/cleaned Injectors

They are currently waiting on more direction from Indmar

My additional ideas:

  • Fuel pressure live readouts (if they didn't already)
  • TPS Live readouts

Friend suggested fuel pump driver in ECM

 

Any other ideas?

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  • iliketoski changed the title to Solved:I'm Stumped, sputter, high idle

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