258 carbed motor runs like crap and dies alot

[rick]

Right on man, gotta start getting the bits and pieces together for the junkyard EFI. The 4.0 head is still at the machine shop, so I'm still in no rush...the price tag is steadily growing, and I am trying to make it grow *slowly*...lol. I'll post the details in the other thread on the 4.0 head/EFI swap.

:shades:

[Dukes69]

Originally posted by Adam
Well, i got all the timgin set and its running really good now. Except i got it going this morning and it died and wouldnt start. I think i got to mess with the choke, i think its stickin. So i have to do a bit of work.
- Change pitman arms
- Replace valve cover gasket
- Fix the choke
- Put revolver shackles on

Glad to hear its working out, for the most part

[MIKE89YJ]

This worked for me !!!

I drive an 89YJ with the Carter BBD carburator and this simple fix has solved my problems as well as several of my friends. Only takes a couple of minutes to do.

Easy Fix for Jeep 258 Carter BBD Idle Problem
by Terry L. Howe


The Jeep 258 (4.2L) I6 isn't a power house, but it has gobs of low RPM torque that makes it a great engine off-road. The most common problem I see with the engine is it's inability to idle. Between the 258 in my '81 CJ-7 and a couple friends that have 258 equipped Wranglers, I have fixed this problem half a dozen times and the cause of the problem has always been the same. The problem has always been caused by clogged idle tubes that cause fuel to drip out of the venturis and make the Jeep run rich at idle. Fixing the problem is relatively easy and once you get past this problem, you will get much more enjoyment from the 258 and the Carter BBD carburetor.
The Carter BBD is a two barrel carburetor that was available on late 70s to late 80s Jeeps with the 4.2L engine. There are two variations of the carburetor, one is computer controlled and has a stepper motor on the back side. The computer controlled version was used after 1981. Other than that, the two versions are the same although it seems the stepper motor version is a bit more troublesome.
The Symptoms
The symptoms of the problem include stumbling and sputtering at idle. In advanced cases, the Jeep will stall at every stop sign and will only run at high RPMs. Gas mileage will suffer since fuel will just be sloshing out at idle. Sometimes the idle will be turned up to a high RPM to avoid the problem. Typically, the Jeep will run fine at higher RPMs (unless there are also other problems.)
For a sure diagnosis, park the Jeep with the engine off and remove the air cleaner cover. There should be a plate over the throat of the carb, the choke plate. If you open the choke plate you should be able to see down the throat of the carb and you should see two screws with holes in the middle of them. Next to them are two passages with a nozzle in the middle of each. This thing is known as the venturi, when air passes by, fuel is supposed to be drawn out through the nozzles. If the idle tubes are clogged fuel will drip from those nozzles during idle.
In order to see if fuel drips from the nozzles at idle, you must start your Jeep with the air cleaner cover off and look down the throat of the carb. The Jeep Technical Service Manual recommends that, when you do this, you cover the air cleaner with a piece of plexiglass since the engine can backfire through the carb and a flame can shoot out. Since I am reckless and like living dangerously, I never do this.
After you have chosen the wise or foolish path, start your Jeep and open the choke plate. If your idle tubes are badly clogged, you will see fuel dripping from the nozzles at idle (if your Jeep will idle at all.) If you don't see fuel dripping, but your idle is still poor, open the throttle a bit with your hand or have a friend hit the accelerator. You should see two even streams of fuel and no dripping from the nozzles. Any dripping means clogged idle tubes.
While you are doing this, make sure you don't put your hand or anything else into rotating parts like the fan. Keep your tie away from that thing (some people just want to look good all the time.) Same goes if you are a "long hair, freaky" Tesla type. All joking aside, I've heard some bad stories.

The Solution
Neither removal of the carburetor nor a complete rebuild is necessary to fix the problem. To fix the problem, start with you Jeep off and parked securely:
1. Remove the air cleaner cover and air cleaner. You may need to remove a few hoses and wires to get the air cleaner out of the way. Make sure you tag them all so you can put them back in the right spot. It's often easiest not to remove the heater hose that goes to the exhaust manifold, if you have one.
2. Remove hoop that holds air cleaner.
3. Remove the two screws holding the choke plate with a 3/16" socket or small flat blade screw driver depending on what screws you have holding it. Be careful not to drop the screws down the manifold unless you enjoy fishing. Remove the choke plate.
4. If your carb has one, remove the plate on the side that covers the choke linkage so you can access the screw holding the choke rod. It may be necessary to drill out a rivet to get it free.
5. Remove the little snap ring and screw (1/4" socket) that holds the rod that holds the choke plate and remove the rod. A screw driver will normally push off the snap ring.
6. Remove the two screws with holes in the middle of them and carefully remove the venturi cluster with the two little gaskets. There should be two idle pickup tubes pushed into the venturi sticking out of the bottom. If they have fallen out, that could cause your idle problem.
7. Blast the venturi and inside of carb with lots of carb cleaner. Be sure not to dislodge the check ball in the center.
8. With a long thin pin or piece of piano wire, make sure the idle tubes and nozzles are clear. After you have run them through, spray with more carb cleaner.
9. Put the cleaned out venturi cluster back with the two gaskets and two screws.
10. Replace the choke rod with snap ring and screw and replace the choke plate. Make sure all the screws are tight that hold together the carb body at this time. Often the screws will loosen up and dirt will be sucked into the carb.
11. Replace the plate covering the choke linkage with a sheet metal screw, or leave it off.
12. Replace the air cleaner.
Smooth idle should have returned after this simple process. If you still have idle problems and don't have any dripping, make sure all the vacuum hoses are hooked up and in good shape. Also check for leaks around the intake manifold or a loose carburetor.
To avoid repeated clogged idle tubes, drill out the idle tubes to 0.032". This will greatly reduce the frequency of clogging and it is a procedure that was actually recommended by Jeep for a while.

[Sully]

Ive still got the carter carb.When I bought my jeep,it ran horibly and had NO power and counldnt idle.I had conejo carb rebuild another carter carb and it runs like a top!It would be nice to have fuel injection,but it is too expensive.

[rollbar]

Why not just go w/the MC-2100 carb & get an adapter plate to fit the 258!


Just a thought,

RollBar

[rick]

The Carter fix is free, and it does work. Sully, did the carb shop re-bush the throttle shaft? This is usually what wears out on the Carter, and in their infinite wisdom, they designed the carb body without any bushings for the throttle shaft. This is by far the most common problem with Carter carbs, they develop a huge vacuum leak around the throttle shaft that can only be fixed by machining out the body and installing bushings. This is usually more expensive than getting a MC2100. Buyer beware on "remanufactured" Carters...they usually don't install bushings on the throttle shaft. I almost bought a rebuilt Carter from Napa, and when I pulled it out of the box, I noticed that the throttle shaft was almost as sloppy in the housing as my old one...

[Sully]

I am not sure.