3.0LX Idling Problems (wont idle below 1k rmp)

[brsox88]

So I have a 1996 3.0LX Merc. I have replaced the fuel filter, fuel pump, carb with a rebuilt Rochester carb, and the starter. Engine runs great once you get it started, however I have been tweaking the carb and I think I got it dead on except for the fact I cant bring the idle down below 1100rpm without the engine starting to shake and want to die.

Checked the carb after running and saw what looks like water deposits on the carb fins (bad terminology) or maybe its just gas. What should I check first or try first?

 

[Don S]

Re: 3.0LX Idling Problems (wont idle below 1k rmp)

Unless you have a water seperating fuel filter installed, the filters in the carb and fuel pump will NOT keep water out of the carb. If you don't have one, install one. If you have some water in the tank, it may need to have the water removed or it will just keep filling up filters.

 

[franktrav]

Re: 3.0LX Idling Problems (wont idle below 1k rmp)

fast idle that wont come down is a symptom of a vacuum leak...check for leaks around carb base,. and intake manifold /cylinder head joint....even the throttle shafts on carb can leak vacuum if worn bad enough
with engine running,spray a small amount of carb cleaner/starting fluid around theses areas.....if the rpms change,youve found your problem
use caution spraying this stuff around hot engine/very flammable
goodluck

 

[brsox88]

Re: 3.0LX Idling Problems (wont idle below 1k rmp)

fast idle that wont come down is a symptom of a vacuum leak...check for leaks around carb base,. and intake manifold /cylinder head joint....even the throttle shafts on carb can leak vacuum if worn bad enough
with engine running,spray a small amount of carb cleaner/starting fluid around theses areas.....if the rpms change,youve found your problem
use caution spraying this stuff around hot engine/very flammable
goodluck

I think that may be what it is because even when I get the carb down to the lowest it can be set to idle I still hear like a hissing noise very much like air is being sucked in somewhere else. I have no idea where, so I will test it out tomorrow. I did noticed when it was flooding and backfiring gas was leaking out of the throttle shaft like you said.

 

[franktrav]

Re: 3.0LX Idling Problems (wont idle below 1k rmp)

. I did noticed when it was flooding and backfiring .

kinda opens a whole nuther canna worms ya know

 

[kd7isf]

Re: 3.0LX Idling Problems (wont idle below 1k rmp)

Sounds like you might have a couple issues......

First thing is you need a fuel/water filter, as suggested above

My '74 started doing this and when I opened up the carb, I found the float corroded solid in the down (open) position. So, I rebuilt the carb, just to have similar issues two runs later. This time I was able to clean it and lube it to make it work right. At that point I installed a fuel / water separator and the problem has yet to come back....

you said you had fuel coming out around the throttle shaft -- if fuel can get out, air can get in.... You may need to have bushings installed on your throttle shaft or simply get a rebuilt carb....

Without the flooding comment above, my first thought would be to check the firing order. The info on the flame arrestor (air cleaner) is printed incorrectly on late '90's 3.0 lx's-- your plug wires may have been installed wrong last time you had a tune up because of this... Correct order is 1-3-4-2 (1 is the front cylinder)

Hope this helps