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View Full Version : 2005 197 MCX Engine - Missing/Running Rough


BuoyChaser
04-25-2006, 03:35 PM
my dad just picked up his 2005 197 w/ MCX Engine and took it out for the first time this past weekend...he felt and heard a noticeable miss at idle...any thoughts???

they didn't ski but

he did winterize the boat himself, followed all the steps in the manual...

he had put Stabil in the tank this past year...but didn't put in any fresh fuel or octane booster...

BuoyChaser
04-25-2006, 05:40 PM
the dealer indicated that octane degrades over time, and that just over the winter season 89 octane becomes 87 octane or even lower???

G-man
04-25-2006, 05:47 PM
Is the knock sensor wire reattached to the knock sensor? Just thinking outloud.

east tx skier
04-25-2006, 06:07 PM
Even with stabilizer, fuel will degrade over time. Maybe try throwing some 93 in there and running it through.

/spitballing, bumping, waiting for the big guns.

Footin
04-25-2006, 06:35 PM
New gas and drive it like you stole it.

Or maybe it's never going to be right.....yeah, sell it to me very cheap.
Yeah, thats the ticket!

east tx skier
04-25-2006, 06:53 PM
Is the knock sensor wire reattached to the knock sensor? Just thinking outloud.

Maybe the newer ones are different, but on my father-in-law's 98 205, the knock sensor is part and parcel to the starboard sign engine drain plug.

PendO
04-25-2006, 07:51 PM
if it "missed" at idle the knock sensor wouldn't come into play (regardless of if it is plugged in or not) ... I don't believe that the ECM starts to "look" at the KS until higher RPM's (JimN - is this true?)

Regardless ... perhaps you will want to take a look at the spark plugs and maybe just replace them. Also, I like to start the year by adding octane and injector cleaner - but I'm by no means a mechanic.

Also, as for the Stabil ... this thread was interesting, maybe a dealer or JimN can let us know (http://www.tmcowners.com/teamtalk/showthread.php?t=693&highlight=stabil)


faq's about Stabil (http://www.goldeagle.com/sta-bil/faqs_stabil.asp) --- was the Stabil added to brand new gas, or just the gas that was in the tank at the end of the year?

tommcat
04-25-2006, 08:39 PM
is it a definite "miss" or just an overall "runs rough" condition?
if it is clearly missing and dropping a cylinder i would look at the plugs and the wire ends that go onto the plugs. moisture over the winter can cause some serious chia pet growth on there. clean them up with electrical cleaner and put some dielectric grease in the wire ends.
finding a misfire is fairly easy, especially if it will do it at idle and doesnt need to be under load.

if it just generally runs rough then i'd look for a fuel concern.

G-man
04-25-2006, 09:12 PM
Maybe the newer ones are different, but on my father-in-law's 98 205, the knock sensor is part and parcel to the starboard sign engine drain plug.


Your correct eastie but there is a wire that attaches to it, on some newer not to be named boats the knock sensor screws directy into the block, not into a drain like I saw once on a mosoon.

east tx skier
04-25-2006, 10:01 PM
Gotcha. That's my new fact for the day.

BuoyChaser
04-25-2006, 10:44 PM
it will be the weekend before he can check it out and drop it in the water to really give it a go!!!GREAT THOUGHTS!!!

sand2snow22
04-25-2006, 11:59 PM
the dealer indicated that octane degrades over time, and that just over the winter season 89 octane becomes 87 octane or even lower???

Tommcat is probably right or it could be bad gas? I have a question. Did it run rough all the time at idle or only when it was cold? I have the MCX and mine ran a little rough until the fogging oil had burned off, then it was fine.

I think there is another post floating around about someone losing two cylinders on the MCX. If it runs rough at idle all the time, I would guess a fouled injector. Maybe put good gas in, run it, see if it still misses. If it does, take it in, plug it in and scan for codes....

BuoyChaser
04-26-2006, 01:19 AM
Tommcat is probably right or it could be bad gas? I have a question. Did it run rough all the time at idle or only when it was cold? I have the MCX and mine ran a little rough until the fogging oil had burned off, then it was fine.

I think there is another post floating around about someone losing two cylinders on the MCX. If it runs rough at idle all the time, I would guess a fouled injector. Maybe put good gas in, run it, see if it still misses. If it does, take it in, plug it in and scan for codes....
he's going to try running 93 gas in it tomorrow and at least check the knock sensor...

BuoyChaser
04-27-2006, 10:45 AM
here's what my dad had to say:

"The knock sensor was connected as I checked it at the Lake House. I will try the 93 octaine and some dielectric grease for the plug tips. The miss is not noticable at idle only at above idle speeds. Seems like a cylinder missfire, no popping or banging and no hesitation on acceleration. Hope its just bad fuel or "cob webs" from laying idle over the winter."