Can I Cop a BREAK!!!!!

[tengals123]

What does a man have to do......<br /><br />1998 Mercury 115 2+2 was running ok, and developed a hard miss every 3-5seconds after it warmed up. Rebuild 4 carbs, pulled again a re-checked, they are spotless. New plugs, new filter have swapped cdm's around, none of this has made any difference at all. Runs ok at high rpms, I think. It's almost like someone pulls a plug, the motor sudders, drops 400rpm, coughs, splutters, blows a huge puff of smake and kicks back in again, only to repeat it again 3-5 seconds later?<br /><br />PLEASE HELP if anyone has any idea's.<br /><br />cheers

 

[Laddies]

Re: Can I Cop a BREAK!!!!!

Sounds like one of the CDM is going bad

 

[tengals123]

Re: Can I Cop a BREAK!!!!!

thanks for the reply laddies. I swapped cdm 1 and 2 with 3 and 4 it made no difference. Am i missing something?<br /><br />cheers

 

[JB]

Re: Can I Cop a BREAK!!!!!

Water in the fuel?

 

[tengals123]

Re: Can I Cop a BREAK!!!!!

running from a portable tank now with 3 day old fuel. still no difference. <br /><br />cheers

 

[Dunaruna]

Re: Can I Cop a BREAK!!!!!

Sorry if this is a dumb question but wouldn't swapping the modules around just MOVE the problem to a different cylinder - not isolate the problem?

 

[papasmurf]

Re: Can I Cop a BREAK!!!!!

You might try a timing light or an inductive tach on a plug wire as the motor is running. Watch the timing light or the tach as the problem occurs. Move from one cyl to the next to isolate an ignition problem.

 

[tengals123]

Re: Can I Cop a BREAK!!!!!

thanks for the responses. Aldo, 1and2 fire below 1800rpm, so by swapping 1and2 with 3and4, essentially im providing a new set on the 1and2 cylinders that fire at idle only.<br /><br />To add a little more to the equation.<br />My idle screws are out 1 1/2 turns from seated. My idle speed adjustment is at minimum (it cannot go lower) and my idle rpms are at about 1200-1500rpm. I cannont get it lower than that. Question - Could all this be as simple as my idle timing being out a fair bit? If the idle timing is out would I have a super fast idle that would miss like this?<br /><br /><br />cheers

 

[papasmurf]

Re: Can I Cop a BREAK!!!!!

What rpm are you experiencing this problem?

 

[tengals123]

Re: Can I Cop a BREAK!!!!!

UPDATE - looks like it was a timing/carb sync issue. Idle was set like 10 deg. ATDC has been reset correctly. I have not adjusted the idle mixture screws yet so running a little rough on the muffs but definetly NO MISS anymore. I will water test tomorrow and let you all know the result. Seems happy atm to sit at 700rpm, in neutral at idle.<br />GOOD new for once I guess.<br /><br />cheers