2003 3.0L dies in idle after mercarb rebuilt

[jack black]

A couple of people mentioned on this board that chances of successful carb rebuilt is only 50/50.

They may be right. While the engine works strong at 1000-4000 RPM, it often dies at idle speeds. Sometimes it doesn't. When it doesn't, the idle speed is ~800 RPM and engine is smooth, except for some ticking valves (my next project).

It's annoying during docking maneuvers and I have to deal with this by revving to over 1000 RPM in neutral and slamming in gear before it dies. Also, warm starts require 1 pump of fuel, something that was not necessary before. A/F mixture used to be rich as evidenced by carbon fouled plugs. Now, the plugs look really clean and nice. This is weird as the jets were not changed. Also, I used to have bad dieseling. Not anymore.

The idle mixture screw was replaced as a part of the kit and it's now 1.5 turns, as opposed to 2 with the OEM screw. It was adjusted based on the highest RPM at idle. Should I bump the idle speed to over 800 RPM tom prevent dieing? I'm afraid dieseling will come back.

I also though about anti-siphon valve as idle problems show up after a while. But the gas starvation problems would be at high RPM and not low, right?

Thanks!

 

[littlebookworm]

Re: 2003 3.0L dies in idle after mercarb rebuilt

Who did the carb rebuild, you or a mechanic or a carb shop? Obviously, there are problems with the rebuild, and it should be redone. Playing with the idle speed will not fix the problem. The carb must be disassembled, soaked in strong carb cleaner, and blown dry. A quality rebuild kit must be used, preferably OEM. All bushings must be checked for wear. All gaskets, O-rings, and other wear-items need to be replaced. Float and needle setting must be exact. Rebuilding a carb is not a 50/50 proposition if done correctly. Almost all carbs can be rebuilt to as good as new condition if done correctly. Hy

 

[fat fanny]

Re: 2003 3.0L dies in idle after mercarb rebuilt

Verify tach is accurate! 50/50 you may have not cleaned it as well as you thought you may have picked up some debri in the passages. Soak,blow out and scrub then repeat!

 

[jack black]

Re: 2003 3.0L dies in idle after mercarb rebuilt

Thank you both for feedback. Since this was my first carb rebuilt, it's possible I screwed it up. But, I don't think I left any dirt in it. All passages were squeaky clean and patent. The more I think about it the mixture needle setting must be wrong. The OEM setting is supposed to be too lean. The new setting is even leaner (screw turn wise). Initially I thought it was due to difference in needle. I'm not so sure anymore. I will try going back to the stock needle and stock setting. I will also replace anti-siphon valve just in case. If that fails, I will take the carb apart again.

 

[Jmunk]

Re: 2003 3.0L dies in idle after mercarb rebuilt

As far as the mixture screw is concerned I'd start at the 1.5 turns out and go from there. It might take 1/2 or more to get it to where it runs good, 1.5 is only a starting point. However you shouldn't have to it 3 turns out to idle good either.