Poor Idle Just Started

JedCrone · #1 April 15th, 2019, 09:12 AM

Hey there I have a 351w in my F100. The engine is from a '78 LTD. The other day it started idling poorly. I would come to a stop and it acted like it would die. As soon as I gave it gas it was fine. When in park it would still idle weird but wouldn't be close to dying. I checked it out and I saw the accelerator pump was leaking every time I gas it gas. Replaced that which is good but it of course didn't affect the idle problem. My two thoughts are either power valve or fuel pump. It acts like it doesn't have gas tho, on a full tank, so I'm thinking it's a fuel pump. Any advice on how to move forward? What to test? What it might be?

Thanks

**glc** · #2 April 15th, 2019, 09:26 AM

Sounds like the whole carb needs a rebuild.

harrison28 · #3 April 15th, 2019, 09:33 AM

Power valve operates at low vacuum, (more throttle). Your metering block may need to be cleaned out. When is the last time you rebuilt your carb?

JedCrone · #4 April 17th, 2019, 08:11 PM

I just rebuilt it today after glc suggested it. Not I cant get it to smooth out to save my life. I replaced the power valve and accelerator pump again cause the one I just put in looked like it was about to fall apart already. I put a new needle in for the float and a new seat. I took out all the jets i could and sprayed them out. I cleaned everything I could by spraying it down with carb cleaner and wiping stuff off. Put it back together with new gaskets. Then I put it back on the engine. Every time I turn both idle mixture screws 1.5 turns out to start but I can't get it to idle smoothly even if i adjust them at the same time 1/4 turn at a time. It doesnt seem like the truck wants to die anymore unless I adjust the mixture screws almost closed so maybe i fixed my old problem, but now theres a new one.

**glc** · #5 April 17th, 2019, 11:44 PM

How are the spark plugs, wires, cap, and rotor? Have you done a compression test?

Note that ethanol fuel will cause it to run lean, and also gums up the fuel system.

JedCrone · #6 April 18th, 2019, 10:33 PM

As far as I can tell the plugs and wires are fine. Nothing looks worn and everything is tight. Tried messing eith it again today but it wouldnt stay running without my foot in the gas. I'm going to clean it again and see what happens. I'll be more meticulous this time.

JedCrone · #7 May 8th, 2019, 09:18 AM

Turns out it was the carburetor. I believe I fixed the original problem by cleaning it. However, when I took the fuel filter off, I noticed some kind of jb weld type material on the carburetor where the filter screws in. I cleaned some of it off and found a crack in the carburetor casting. I didn't really think about it but as it turns out, that's where the new vacuum leak was created. Threw a $100 Amazon carb on and it runs like a charm now. I have a YouTube channel under the name Jedidiah Crone where I will be posting a video on it soon.