Low RPMs engine quits

[Fstued]

MY old A4 starts no problem with choke out at 2K rpms I can then put the choke in and drop the rpms down to about 1.2k Then for there down it just dies quickly as soon as I try bring her to idle speed, 800 rpms she dies. That's in idle with load on her she dies quicker at about 1200.
I am assume it is a carb problem I haven't messed with the carb in probably 400hrs. So does that mean a new carb (rebuilt) or just a good cleaning for this one? I have already taken the carb off the block. Thanks

[BunnyPlanet169]

Fstued - Welcome to the Forum!

Rebuild or clean out the one you have. You can go a long way with a good aerosol carb cleaner and some piano wire or old guitar string.

There is a carb-cleaning knowledge-base video for sale from our sponsor that is totally worth the $12 or so it takes to watch it. MMI has the rebuild kit as well, along with the gaskets.

One thing I'll stress every time we talk about carb cleaning with solvents or compressed air - wear goggles. See how big these eyes are? The carb is like a crazy dribble glass that shoots fluid back at you from unexpected places.

PS - don't rule out fuel delivery/fuel pump. Do you have a fuel pressure gauge?

[Fstued]

Thanks I'll give the cleaning a try and the video too
Stu

[Al Schober]

Your engine should idle smoothly at 800 rpm - IN GEAR!
First step is a smooth low idle in neutral. Yes, carb is a likely suspect, but only one of many. Give the carb a good cleaning (it's like therapy), and if that doesn't do the trick we'll come up with some other things to check (compression, vacuum leaks, etc).
Don't despair - the A4 is a fine engine. Some are getting a bit aged and need some remedial care, but that's the name of the game. For my boat and my wallet, it's a better game than going diesel.

[capnward]

into the magic of zenith

Fstued,
400 hours? Yes, I bet if you clean your carb all will be well. The Moyer video is a big help. I had symptoms like yours, she wouldn't run at idle. It turned out to be a barely visible obstruction in the tiny idle jet. I couldn't see the blockage until I removed the jet, held it up to the light and looked through it. I took a wire from a wire brush and worked it around in the jet. I also shot carb cleaner through it and the other jets, dressed the seat of the float valve with the pointed wooden dowel that comes with the rebuild kit, and put it all back together with a new gasket. New inline filter too. Problem solved. That was a good feeling. Al is right, it's like therapy.
Run a wire through the idle ports in the throat while you're at it. Also remove the idle adjustment screw and shoot cleaner through its seat. You probably won't need to replace jets, but it will nice to have the kit. File a screwdriver down, to fit the idle jet without digging into the threads around it. Buy several gaskets.
Welcome to the A4 carburetor; keep it clean and it will be your friend.

[marginal]

When my exhaust started leaking, the first thing I noticed was the engine would die at idle, which it never usually did.
Then the CO detector went off, then I discovered the leak.

Good luck with the fix
Simon

[Fstued]

all good info

Thanks for all the info I am pitting it back together now. The gaskets just arrived. Do I need gasket sealer on the gaskets?
Thanks again
Stu

[sastanley]

On the carb I would not use gasket sealants. 400 hours without a carb cleaning is living large. Don't forget the small idle orifices between the butterfly on the carb as you clean. Stripped bread ties usually work good for this.

My personal experience is that I need full choke to start...and after 3 or 4 seconds I run 1/2 to 1/3 choke for another few minutes while I let the engine warm up and I remove dock lines. Once I power up out of the slip, I can generally go to zero choke.