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8.1 Litre Problems


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2004 Malibu LSV with 8.1,  been to 3 shops and 9000.00 spent.

Problem : First start of day takes 4-5 times to start. If you fast idle to start 2 times to start.

Major Idle flare , had all updates done , most times when you come from in gear (forward or reverse) it flares up to 1500-1800 Rpm then back to 850. Replaced IAC,TPS , Temp Sensor, 2 Computers , camshaft and crank shaft sensor, MAP sensor and Knock senor. Two different shops checked for latest version.

Idling around lake , it vibrates and runs rough, almost like its over camed.  Have had computer hooked up no codes. New plugs , replaced intake gasket around Throtle body, leak checked around intake while running.

Fuel pressure checked , compression checked.

If you run on fake lake it runs better, run in pit or water the increased back pressure seems to make it worse.

Looking for some ideas. What to do next.

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Could this be something in your drive line?  Trans, vdrive, shaft or strut?

 

Does it run rough only when in gear?  It sounds like you are saying it runs rough in or out of gear.

Edited by Shine
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The fuel pressure was checked in water at idle and mid throttle. It was well within limits. New fuel filter was tried. It's rough up to approx 1000 rpm. Then it smooths out. Fresh fuel always. Put 50 hrs on boat this year. Always tried to use 93 octane.injectors haven't been tested, is that something that can be tested without special tools.   Biggest change was when shop reset IAC valve. Started crappie, but ran smooth. That's why another new IAC was tried,no luck.  

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On 9/28/2017 at 10:58 AM, Rolodex said:

If you run on fake lake it runs better, run in pit or water the increased back pressure seems to make it worse.

Could you clarify what this means?

Seems like these marine engines are not highly tuned and don't really need 93 octane...the higher octane could actually be working against you.  So with that said, I'd try using regular fuel and see if anything changes.  Also try a high dose of fuel injector cleaner.  I never believed that stuff worked until I saw it work firsthand. Can't hurt, can it?

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On 9/28/2017 at 3:45 PM, twitchee2 said:

Fuel filter?

Sadly enough I am leaning this way.  I have an 8.1 and can link you to my issue page but man I would change that filter.  I know you think no but do it.  I chased mine for 3 weeks sensors and all and it was fixed only by a new fuel filter.  Mine was major flare under load.  Sometimes very hard to start.  I have read this thread a few times and keep going back to it.

 

I am not a fdan on wires only because of the intermittent issue with flare.  Feel the wires while running kind of sucks but you will know quickly if you have spark jumping around.  Maybe a slight mist while running in dark will help save a shock.

 

But I sat fuel filter.  They are solid engines, I would be getting a refund in those computers too.  That is cheap if it does not fix the issue.  I can see 1 but if that did not work, if another was attempted why was it not free from original source.  I would look into that.

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9 hours ago, NHolladay said:

Sadly enough I am leaning this way.  I have an 8.1 and can link you to my issue page but man I would change that filter.  I know you think no but do it.  I chased mine for 3 weeks sensors and all and it was fixed only by a new fuel filter.  Mine was major flare under load.  Sometimes very hard to start.  I have read this thread a few times and keep going back to it.

 

I am not a fdan on wires only because of the intermittent issue with flare.  Feel the wires while running kind of sucks but you will know quickly if you have spark jumping around.  Maybe a slight mist while running in dark will help save a shock.

 

But I sat fuel filter.  They are solid engines, I would be getting a refund in those computers too.  That is cheap if it does not fix the issue.  I can see 1 but if that did not work, if another was attempted why was it not free from original source.  I would look into that.

I don't think he said it was intermittent, I think he said it was at low rpm's.  Those engines are so stout, the other 7 cylinders would make enough power at higher rpm's that you wouldn't notice a bad cylinder.  I had a spark plug wire come loose on my 6.2 this summer and I heard a small miss and had a hesitation and fuel smell starting out of the hole.  Once we got up past 15 mph, you couldn't tell it was off. 

I would definitely check the fuel filter too. 

OP - Where are you located?

Edited by JeffK
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  • 4 weeks later...

The fake lake is the tool used to run on the trailer, the pit is what some shops use. They back the boat and trailer in pit of water an run it. Weirdly it runs better when the exhaust it out of the water ( on the trailer in driveway).  I am located in Alberta.   Will change the fuel filter and look at wires, i can change them also .  Wont be able to test till spring now.

Thanks for input , will report what i find.

 

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  • 6 months later...

New fuel filter , last of the sensors replaced.  Fresh gas, same problems , 2 -3 times to start.

Idle flare, all the same as before. Not sure what to do. Nice boat just makes it hard for just anyone to drive it,as you have to wait for the RPM's to drop before putting into gear

Looking for 8.1 owners with solution.

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Throttle body is possibility.   They go out. Opposite end of throttle position sensor but can mimic symptoms.  GM/delco version same but cheaper than Indmar version.  

Also 89 is all that’s recommended for 8.1.  But that’s not your problem 

Edited by rugger
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Get a set of wires on that thing. If you still have originals, it's time anyways. Less than $100.  If thst and a new throttle body don't work, it's time to burn it down.

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12 hours ago, Arick said:

Actually the guy we should be calling is  @barefootrocker

Here's the solution thread:

http://www.themalibucrew.com/index.php?/forums/topic/61153-done-with-my-echelon-vapor-lock/&page=4

It turned out to be such an easy fix for him, hope yours is similar @Rolodex

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Checked all connections on all sensors. Compression check done. Checked screen on inlet side of pump. All good.  

Have bought diacom marine. Will diagnose myself. Will scan this weekend . Have a set of wires on order. 

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  • 4 years later...

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