Volvo Penta 5.0 GXI misses at High RPM

Stuartbp

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Aug 8, 2014
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I have a 2003 Four Winns Horizon with a 5.0 GXI. Engine fires up and idles great, but when I try to go above about 3/4 throttle it starts to miss. No backfire...just quick misses at high RPM. I can punch it full throttle to get it up on plain and she jumps out of the water with no hesitation like a champ. Once it gets on plain and gets up to speed it will start to miss...but only if I try to go past about 4000 RPM...anything less and it runs great.

New plugs and OEM plug wires this month along with distributor cap and rotor...No difference when changed.

New fuel pump in July of 2015.

New fuel filter at twice so far this season....no change in performance...been through a few tanks of gas so gas is fresh...and I have used ethonal free fuel as much as possible this season.

Fresh oil all around at beginning of season...new impeller last season.

Temp is good, oil pressure is good..

Anything else I should be looking at?

I have not changed the fuel lines, but that job requires removing the whole back seat and some other things so that will be an off season job.
 

Scott Danforth

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normally I would say change the cap and rotor.

have you checked fuel pressure?
 

Stuartbp

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Aug 8, 2014
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I thought electrical at first as well...so I did plugs wires rotor and cap but it didnt change anything. I have not checked fuel pressure yet, thought that a brand new fuel pump would mean it should be okay.
 

Poco2

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May 27, 2011
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I believe the 5.0 GXI uses 2 fuel pumps. High pressure and low pressure. Which did you change?
 

Stuartbp

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I did the whole assembly...which has both high and low...cost me 800 bucks...ran fine all of last summer and for the first couple months this season...I'm doubting a fuel pump issue...What gets me is that it runs great under any circumstance, even pulling tubes or skiirs out of the water when fuel demand is huge....Only misses at high RPM
 

Scott Danforth

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I would pull the fuel pump assembly and look for paint clogging the screens. if you have missing paint and the updated assembly without screens, the paint may have made its way to the injectors which now need to be cleaned.
 

89retta

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Jul 18, 2010
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Have you checked to see if your tach is reading correct? Perhaps its reading low and your hitting the rev limiter
 

Stuartbp

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I'm not hitting the Rev Limiter I'm sure of that. I replaced the whole fuel assembly last summer and have used ethenol free fuel for almost every fill up along with marine stabilizer..so I'm really doubting any fuel pump, paint flaking issues...I read up on those before and decided to change out the assembly as a preventative measure after getting some slight hesitation problems upon acceleration from standing. Solved that issue with the new pump assembly.

I can take it off and check it this winter when i have the seats out but its a pretty big job to access in this particular boat.

I'm just confused on why it doesnt miss during hard acceleration if its a fuel problem..Was hoping someone had a similar issue and figured it out already.
 

muc

"Retired" Association of Marine Technicians...
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You didn't post a serial number so it's a guessing game on what fuel and ignition system you have. Yes that can make big difference on what the cause of your problem is.
I wouldn't rule out a fuel problem, I think the engine uses more fuel at high Rpm's than at low Rpm's. Maybe you have too much fuel pressure? Did you check the fuel pressure regulator screen? Hard to hear the difference between a lean miss an a rich miss. When you have a problem like this you really need to check fuel pressure when the problem is happening. Why anybody would disassemble a possibly good fuel cell when it can be simply tested is beyond me. But I'm big on testing and wouldn't work on a EFI engine without a scan tool and fuel pressure gauge. I've had way too many experiences with unusual problems that swapping parts is a waste of time.
There are many things that can cause this miss and if we knew what fuel system and ignition system you have we could make a good GUESS.
But it might be best to have the engine scanned while it's missing by somebody who is good at using a marine scan tool. This would quickly rule out the TPS,MAP,CKP,CMP,IC module, ect. that could be causing this problem.
 
Last edited:

Stuartbp

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Aug 8, 2014
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9
You didn't post a serial number so it's a guessing game on what fuel and ignition system you have. Yes that can make big difference on what the cause of your problem is.
I wouldn't rule out a fuel problem, I think the engine uses more fuel at high Rpm's than at low Rpm's. Maybe you have too much fuel pressure? Did you check the fuel pressure regulator screen? Hard to hear the difference between a lean miss an a rich miss. When you have a problem like this you really need to check fuel pressure when the problem is happening. Why anybody would disassemble a possibly good fuel cell when it can be simply tested is beyond me. But I'm big on testing and wouldn't work on a EFI engine without a scan tool and fuel pressure gauge. I've had way too many experiences with unusual problems that swapping parts is a waste of time.
There are many things that can cause this miss and if we knew what fuel system and ignition system you have we could make a good GUESS.
But it might be best to have the engine scanned while it's missing by somebody who is good at using a marine scan tool. This would quickly rule out the TPS,MAP,CKP,CMP,IC module, ect. that could be causing this problem.

How many differen fuel and ignition systems came on a 2003 Volvo Penta 5.0 GXI anyway? From all the research and work I've done on the boat I'm only aware of one.
 

CV16

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How many differen fuel and ignition systems came on a 2003 Volvo Penta 5.0 GXI anyway? From all the research and work I've done on the boat I'm only aware of one.

Not sure, but is it that hard to post the serial number of the motor?
 

muc

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How many differen fuel and ignition systems came on a 2003 Volvo Penta 5.0 GXI anyway? From all the research and work I've done on the boat I'm only aware of one.

Are you sure you have a 2003 engine? Some 2003 hulls can have an 01,02 or even a 2004 engine installed. Are all 4 years the same engine? Maybe, I don't know. But if you give me a serial number, I can punch it the computer and KNOW right away.

See, wasn't that a better answer then my first response of "if you can't take the trouble to help us --- why the heck should we take the trouble to help you?"
 

muc

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Also, did you know that for two years a MerCruiser engine could come with any one of four different distributors?
But back then a serial number didn't help. The mechanic needed to know the differences between them to get the right parts. Times are better now and a serial number is pretty much needed.

So why don't you tell us if you have BID, prestolite, or EST ignition? Because I'm sorry but I don't remember exactly when they stopped using one and started using another.

Good Day
 

muc

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One more also, just read scott Danforth post. Pretty sure he meant fuel pressure regulator. What he says is true, clogged screens in the injectors could cause this problem.
 

Paul McMahon

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Joined
Nov 25, 2020
Messages
1
I have a 2003 Four Winns Horizon with a 5.0 GXI. Engine fires up and idles great, but when I try to go above about 3/4 throttle it starts to miss. No backfire...just quick misses at high RPM. I can punch it full throttle to get it up on plain and she jumps out of the water with no hesitation like a champ. Once it gets on plain and gets up to speed it will start to miss...but only if I try to go past about 4000 RPM...anything less and it runs great.

New plugs and OEM plug wires this month along with distributor cap and rotor...No difference when changed.

New fuel pump in July of 2015.

New fuel filter at twice so far this season....no change in performance...been through a few tanks of gas so gas is fresh...and I have used ethonal free fuel as much as possible this season.

Fresh oil all around at beginning of season...new impeller last season.

Temp is good, oil pressure is good..

Anything else I should be looking at?

I have not changed the fuel lines, but that job requires removing the whole back seat and some other things so that will be an off season job.
Hi, I have a very similar issue at mid range rpm all the usual stuff done and new ful pump also. Just getting injectors overhauled to see if this resolves the issue.
Did you manage to sort your issue, I know this was some time ago.

Cheers
 
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