How to I go about adjusting a carburetor?

"If only EssExTee could be so grossly incandescent" (essextee) 08/02/2013 at 11:09 • Filed to: None

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Is there like a screw that I turn or something? Ever since the summer weather started the Jeep's had trouble idling when the engine is cold. I'm hoping it's just a simple fix like a carb adjustment, so that's what I want to try first.

We're dealing with a YJ Wrangler with the AMC 4.2. When the engine is dead cold (i.e. sitting overnight) it'll start fine and then immediately die unless you give it some gas. After it's been running for like ten seconds or so it idles just fine.

AddMustard > If only EssExTee could be so grossly incandescent 08/02/2013 at 11:12

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What's a carburetor?

desertdog5051 > If only EssExTee could be so grossly incandescent 08/02/2013 at 11:13

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Possible choke, possible idle mixture.

Is it running rich or lean?

More info.

The Swedish Bandit > If only EssExTee could be so grossly incandescent 08/02/2013 at 11:14

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What kind of carb does your Jeep have in the first place? Anyways there's usually a screw that adjusts the idle speed. Then there's also screws that adjusts the fuel/air mixture, those can be a good idea to get right also.

If only EssExTee could be so grossly incandescent > AddMustard 08/02/2013 at 11:14

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It recirculates exhaust gases back into the engine for better economy or something.

/askastupidquestion

Bret > If only EssExTee could be so grossly incandescent 08/02/2013 at 11:16

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The first rule of carb adjustment is to start with everything else. Often a simple tuneup and check of the timing will clear up problems like this.

What year and model Jeep are we talking about here?

Is there a maze of vacuum hoses running around the engine compartment? Perhaps one of those has come loose or developed a leak?

If the problem is indeed related to the cold start choke not engaging, it could be due to the carb being dirty. Perhaps try cleaning it as much as you can and are comfortable with carb cleaner.

If all that fails, you can always crank up the idle adjustment on the carb. This is the last choice, only do this if you absolutely need to as the higher idle will suck more gas, make it a pain in the ass when putting it in gear, and will make it sound like your car is stuck at high idle all the time.

Good luck!

AddMustard > If only EssExTee could be so grossly incandescent 08/02/2013 at 11:21

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If only EssExTee could be so grossly incandescent > Bret 08/02/2013 at 11:27

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I'll try cleaning the carb, the last time I checked (last week) the hoses were fine. I've updated the post with more info.

Dukie - Jalopnik Emergency Management Asshole > If only EssExTee could be so grossly incandescent 08/02/2013 at 11:31

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CHOKE.

If it starts but needs fuel to stay running when cold, it's most likely the choke. My Celica had an electric choke stock carb, and sometimes the bimetal element goes bad or breaks inside. Might be something to check out.

Bret > If only EssExTee could be so grossly incandescent 08/02/2013 at 12:00

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Yeah, start with cleaning stuff up and seeing if anything is obviously loose. You want all those hoses to have a tight seal. If it sorts itself out after a little bit, I'm betting it's a simply fix.

There's probably a little diaphragm driven gizmo on or very near the carb that controls the cold idle. Make sure that doesn't have any cracks in it and that its linkage is freely moving.

Also look on the carb itself for any signs of leakage or seepage. If there's a tiny little gap somewhere that will let extra air in, that might cause a problem like this. As the carb warms up and expands, the leak closes and the car runs fine. I'm reaching here with this one, but it's still worth looking for.

My experience is with Italian and British sports and racing cars, so I don't have specific experience with AMC drivability issues, but that's where I'd start.

A couple buddies of mine have had Jeeps with the AMC straight six. That's a great engine, tons of torque.

LandSpeed-DSM > If only EssExTee could be so grossly incandescent 08/02/2013 at 13:36

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How did you determine it was a fuel delivery or ratio issue? Have you checked your plugs or timing? Compression or leak-down test?