rough idle???

B

boston_jake01

Seaman
Joined
Jun 4, 2006
Messages
74
I have a 89 volvo penta AQ271C I have done some work on thanks to the help from this site and the BOAT DOCTOR.... my question is the engine sems to run good at about 1300 or above, but when I try to lower the throttle to idle around 800 - 900 it runs really rough and then stalls. Ithought it might be a vacuum leak and placed my had over the carb and it smooth out. I did a vacuum test thru the carb vucuum port for the choke pull off and it registered at 20 and would lower to about 13 or so when it ran rough.
any thoughts? does it seem like a vacuum leak and if so where would the leak come from, I figured it can only be carb and intake manifold.
Thanks
 
stevieray

stevieray

Lieutenant Junior Grade
Joined
Jul 18, 2006
Messages
1,135
Re: rough idle???

Just had the same problem with my 88 Merc 305/ Rochester 4BBL. Years of running & winterizing (sits for 6 months a year here in the Upper Chesapeake region) just took a toll on the carb & I replaced it rather than mess around with rebuilding myself. Runs great with the replacement on.
 
Reel Poor

Reel Poor

Vice Admiral
Joined
Jan 29, 2005
Messages
5,522
Re: rough idle???

Try opening the idle air mixture screwes about a round and see if that makes a difference.
 
B

boston_jake01

Seaman
Joined
Jun 4, 2006
Messages
74
Re: rough idle???

"Try opening the idle air mixture screwes about a round and see if that makes a difference. "

I tryed this no real difference except when I lower the idle down and then turn in the fuel/air mixture screws all the way in.
 
Reel Poor

Reel Poor

Vice Admiral
Joined
Jan 29, 2005
Messages
5,522
Re: rough idle???

What work, that you mentioned, has been performed ?

Is this a Holly carb ? They are bad about the baseplate warping from being overtightened and leaking at the baseplate to manifold gasket.

IMHO it sounds like you have a good reason to clean and overhaul the carb.



 
You must log in or register to reply here.
Top