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Merc 496 problem

Old 06-01-2020, 04:32 AM
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Default Merc 496 problem

I have 2 problems with my 496 that I cant figure out. So I test to post a video of it here so you guys that have much more knowledge than me can watch and maybe give me some advice..
I had a water leak in one of the headers, but in the video I have put the water away from the leaking point.

1. Its idling at 800 then goes up to like 1200 and then down again. Its acting really strange and I dont know what causing this problem.

2. A knocking sound thats not sounds it is related to any mechanical problem. More like something are loose. One guy told me to check the coupler.

Here is a video of the engine running

Thank you

Last edited by JohanSweden; 06-01-2020 at 04:37 AM.
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Old 06-01-2020, 10:46 AM
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I here 2 different things Sounds like you need an new IAC and that all maintenance related to the IAC

the other sound - pull your drive off and run the engine to see what happens
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Old 06-01-2020, 01:01 PM
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Originally Posted by BUP View Post
I here 2 different things Sounds like you need an new IAC and that all maintenance related to the IAC

the other sound - pull your drive off and run the engine to see what happens
Thank you, what is the ”all maintenance” related to the IAC?

It sounds exactly the same with drive off
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Old 06-04-2020, 01:48 AM
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Tror jag äntligen hittade felet på min 496a.
tomgången gick ungefär som din.
men larmade inte för något fel.
hade stadigt soppatryck på ca 40 psi.
kabeln till trimlimit sensorn. Är en 3 ledar kabel.
den delar samma matning som övriga sensorer 5v.
prova o ryck isär den o prova.
förmodligen har jag kortis i själva givaren då den ligger under vatten.
det löste problemet hos mig.
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Old 06-04-2020, 02:01 AM
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Originally Posted by Fimbultyr View Post
Tror jag äntligen hittade felet på min 496a.
tomgången gick ungefär som din.
men larmade inte för något fel.
hade stadigt soppatryck på ca 40 psi.
kabeln till trimlimit sensorn. Är en 3 ledar kabel.
den delar samma matning som övriga sensorer 5v.
prova o ryck isär den o prova.
förmodligen har jag kortis i själva givaren då den ligger under vatten.
det löste problemet hos mig.
Har du möjlighet att beskriva/visa vart den kabeln finns? Kanske ta en bild?
Har dålig koll på vart denna kontakten finns.

Min trim/tilt mätare fungerar inte, den vet inte vart drevet är i för position. Om det är den du menar. Hade verkligen uppskattat den hjälpen så jag kan se om det är likadant fel på min!

är det någon av dessa kablarna?


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Old 06-04-2020, 05:33 AM
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Maybe a broken valve spring
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Old 06-05-2020, 01:08 AM
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Originally Posted by Fimbultyr View Post
Tror jag äntligen hittade felet på min 496a.
tomgången gick ungefär som din.
men larmade inte för något fel.
hade stadigt soppatryck på ca 40 psi.
kabeln till trimlimit sensorn. Är en 3 ledar kabel.
den delar samma matning som övriga sensorer 5v.
prova o ryck isär den o prova.
förmodligen har jag kortis i själva givaren då den ligger under vatten.
det löste problemet hos mig.
Tror jag skickade till rätt person på FB.
Kunde inte svara på ditt Pm här.

I think I got the engine running properly again. Stable at 900 rpm, the knocking sound is still there .. I changed the spark plugs.. I dont know if this was the problem but now it runs

Last edited by JohanSweden; 06-05-2020 at 07:56 AM.
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Old 06-05-2020, 03:27 AM
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What do you guys think? Still the knocking sound tho.
The hose for the raw water is just there because the tailpipes are leaking water.

And what do you guys think about the two bolts that are attached at the back of the engine?
Its 1-2cm up, I tried to tighten them more but they were already tight..


Knocking sound


Last edited by JohanSweden; 06-05-2020 at 03:43 AM.
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Old 06-05-2020, 07:30 AM
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Sure sounds like drive line noise. Whats up with the engine mounting bolts. Looks loose or like washers are missing..
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Old 06-05-2020, 07:33 AM
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Originally Posted by Blueabyss View Post
Sure sounds like drive line noise. Whats up with the engine mounting bolts. Looks loose or like washers are missing..
Do you mean this?
I tried to tighten those bolts but it didnt go



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