80 cj5 4.2l very rough idle unless choke is on

rishar1 · 11-20-2009, 06:24 PM

I have an 80 cj5 with the 4.2l and the factory carter carb. My problem is that it has a rough idle when the choke is not about half way closed and it does the whole stalling when you brake thing. I just cleaned the EGR and it is working fine but most of my other vaccum lines are missing except for the electric choke line and the timing advance line. I'm not quite sure where the other vacum lines go but im sorting that out. I'm just wondering what the hell is causing it to idle like this i even put a rebuild kit in it and it still runs like s***.

**Mike Romain** · 11-20-2009, 07:19 PM

The intake manifold bolts like to come loose, so does the carb base. I would spray some WD40 or carb cleaner along the seam where the intake meets the head and the carb base looking for the vacuum leak.

Here is a thread about the basic vacuum lines: Vacuum Hose Hook Ups - JeepForum.com

rishar1 · 11-20-2009, 08:25 PM

Read that in another post. tryed it didnt work im afraid. I have also noticed that in many threads the mixture is controlled by a stepper motor. my carb has 0 electronics going to it other then a single line going to the electric choke. I dont know if im missing pieces or if i have a different carb. Also my front cto valve only has 2 barbs on it and in alot of the diagrams i have seen there is 3 or more could it be the wrong valve the PO just stuck in there. the diagram I'm looking at now shows a third barb fitting on the forwards cto going to the manifold. but again no extra barb and no manifold fittings. I will post pictures tommorow maybe so you can see whats goin on.

thanks alot Allen

**Mike Romain** · 11-21-2009, 07:12 AM

Sounds like you are reading about the 'computer' controlled carbs and emissions systems that use a multi CTO valve and a feedback carb. You don't have that. That is usually in 82 and up CJ's

OK, so no leaks then. Next I would guess that the idle pickup tube's crimped ends have gotten blocked. They are basically too small and block easily.

Here are a couple articles about testing, cleaning and oversizing those so they don't block so easily:
Easy Fix for Jeep 258 Carter BBD Idle Problem - - Jeep at Off-Road.com

Carb

rishar1 · 11-21-2009, 09:06 AM

Just checked the carb and the driver side venturi is driiping fuel real bad. I will try and fix it tonight as i am at work now. I will let you know if this solves the problem or not.

rishar1 · 11-21-2009, 11:22 AM

That fixed it went ahead and fixed it on my lunch break the tube was almost completly clogged. So the problem I've been trying to fix for 3 months turned out to be a 10 minute job. Thanks for all the help mike.