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Flex400

Misfire under load 07 vlx

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Flex400

Hi guys I've got a 2007 vlx with a 320 lcr that has a misfire only under load,  when I'm in neutral and rev it it runs fine and when I'm full throttle driving along it is fine it's only when I take off as I do to pull a boarder out of the water it has this misfire and when traveling along any cruising speed, now I've replaced the plugs, wires, rotor button, cleaned the distributor cap, fuel filter and made sure there was no water in the tank I also pulled all the injectors and had them flow tested and all was good so can anyone help with what to try next any help would be appreciated.

 

cheers Al

 

 

Edited by Flex400

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gorilla

Actually change the cap. Even though it looks good, there can be a break in the metal strips inside the plastic somewhere. You may even want to swap out the coil. It may not be providing enough oomph to the plugs under load and the spark is getting blown out. 

Good luck, ignition problems suck. 

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Flex400

Thanks for the reply gorilla

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electricjohn

Hesitation on throttle up is usually an indication of a vacuum leak.

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oldjeep

might try putting a fuel pressure gauge on it and have someone watch it as you power up.

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Flex400
On 03/03/2017 at 0:27 PM, electricjohn said:

Hesitation on throttle up is usually an indication of a vacuum leak.

Electric John it doesn't actually hesitate when u take off it pulls from take off like u wouldn't believe its only when under load its hard to explain.

 

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Flex400
On 03/03/2017 at 1:38 PM, oldjeep said:

might try putting a fuel pressure gauge on it and have someone watch it as you power up.

Yes that will be on the cards I've ordered a new distributor cap and should see that early next week.

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malibuparadise

I had a problem similar to you. It was a bad valve. Have you checked cylinder compression. It's not that hard to know.

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Flex400
13 hours ago, malibuparadise said:

I had a problem similar to you. It was a bad valve. Have you checked cylinder compression. It's not that hard to know.

No I haven't did yours idle smooth as silk? Please tell me what what yours was doing?

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malibuparadise

Yes she did idle fine, but when she was on the hose and you disengaged the transmission and gave good gas to her you could hear the dastardly misfire. Checked compression, and YUCK--head job and one new exhaust valve.

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Flex400
23 minutes ago, malibuparadise said:

Yes she did idle fine, but when she was on the hose and you disengaged the transmission and gave good gas to her you could hear the dastardly misfire. Checked compression, and YUCK--head job and one new exhaust valve.

Ok, did u just fix the valve in question or do the lot?

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malibuparadise

the other valves were ok, so just bought one valve

 

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Flex400
On 05/03/2017 at 3:10 PM, malibuparadise said:

the other valves were ok, so just bought one valve

 

What was the compression reading difference between the good and the bad?

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malibuparadise

About  a 40 psi difference!

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Flex400
24 minutes ago, malibuparadise said:

About  a 40 psi difference!

I've done a cold compression test as my boat is in storage at the moment and they come back at

147, 140, 127, 145

147, 130, 120, 130

so now when I get it out which won't be till mid next week I'll redo but I will do it with a warm motor!

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Flex400
6 minutes ago, Engine Nut said:

You need to find someone with a scan tool and check an adjustment called "Cam Angle". Adjusting the cam angle positions the distributor properly so you don't get cross-fire at higher RPM. The cam angle on your 2007 model engine needs to be 705 plus or minus 5 degrees at 1200 RPM or higher and it can only be checked with a scan tool ... Diacom or Tech-Mate. An automotive scan tool will not work. The cam angle is adjusted by tuning the distributor like you would do to adjust the timing on an older engine.

Thanks for the good advice I'll get onto that.

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Flex400
44 minutes ago, Engine Nut said:

You need to find someone with a scan tool and check an adjustment called "Cam Angle". Adjusting the cam angle positions the distributor properly so you don't get cross-fire at higher RPM. The cam angle on your 2007 model engine needs to be 705 plus or minus 5 degrees at 1200 RPM or higher and it can only be checked with a scan tool ... Diacom or Tech-Mate. An automotive scan tool will not work. The cam angle is adjusted by tuning the distributor like you would do to adjust the timing on an older engine.

Engine nut do u think this is the problem?

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Engine Nut
On ‎3‎/‎7‎/‎2017 at 2:03 PM, Flex400 said:

Engine nut do u think this is the problem?

It is very possible. I would sure want to get it checked. That is a pretty simple engine that does not have a reputation for misfiring. I would want to cross it off my list before I went too deep into other things. It is an issue we have seen.

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Flex400
1 hour ago, Engine Nut said:

It is very possible. I would sure want to get it checked. That is a pretty simple engine that does not have a reputation for misfiring. I would want to cross it off my list before I went too deep into other things. It is an issue we have seen.

Ok great thanks for the information I'll get it checked out for sure.

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Flex400

Ok so I finally had some time to do a bit of work on the boat today I put the new distributor cap on but haven't water tested it yet but I did do a compression test. After I got the motor up to running temp here is the results  130, 125, 120, 133 other side was 130,118, 112, 130 so they are more even than when I did the cold test, one thing I did notice was since I changed the plugs the miss has slowly gotten worse and when I pulled the plugs today I noticed on the side of 1,3,5,7 they are a bit oily now the old plugs I pulled out where a hotter plug by 1 point! The previous owner had put these in when he had it serviced what would the reason for putting a hotter plug in? Any info would be great guys.

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Ndawg12

Shouldn't all cylinders be within 10% of each other?

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Flex400
Just now, Ndawg12 said:

Shouldn't all cylinders be within 10% of each other?

Dawg that's what I have read as well but when I have spoke to a few engine builders they said that these numbers was fine, at this point I'm more worried about the oily plugs!

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Flex400

Ok so I have a update on the situation. I was out wakeboarding yesterday for about 7hours and the problem started to become worse it has started to serge so my thoughts it's something to do with fuel so today I did a little research and seen that there is 2 filter socks in the fuel tank on the end of the fuel pump so I pulled the fuel pump out to clean it and hell was there some crap in there as well as the new fuel filter that I only fitted about 2 weeks ago was full of crap but the tank it's self was clean, so I put it all back together and took it for a test on the river hoping it would be fixed not likely it's now 10 times worse, I'm thinking there's that much crap in there that more must of dislodged and it's now in the pump causing mayhem, I'm going check the fuel pressure during the week and go from there! Hopefully a new fuel pump will be the fix.

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Sixball

So without going back through all the posts did you look at the screen at the fuel inlet on the fuel pump? I thinking I saw you did but not sure. Might be worth pulling the fuel line off at the pump and tank and blowing it out with compressed air.

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