Symptoms
Stumbling or stalling at idle and poor economy, but fine at higher rpm. Offroaders.com says the cause is almost always clogged idle tubes. It also says post-1981 feedback carbs with a stepper motor are 'a bit more troublesome.'
The fix, step by step
- With the engine running and choke open, look for fuel dripping from the idle nozzles.
- Tag the hoses, then remove the air cleaner, choke plate and rod, and the venturi cluster (two screws, two small gaskets).
- Check that the idle pickup tubes are seated, clear the tubes and nozzles with fine wire and carb cleaner without losing the check ball, and reassemble.
- Tighten the carb body screws.
- Drilling the idle tubes to 0.032 in reduces clogging.
- If it still idles badly, check for vacuum and manifold leaks.
Tools & part numbers
- 3/16 in socket
- small screwdrivers
- carb cleaner
- fine wire
- 0.032 in drill bit
Where to buy the parts
Carburetor repair kit, 1984 Scrambler 4.2LRockAuto ↗Amazon ↗
Weber K551-38-S 38 DGES carburetor kit, 1972–90 CJ 4.2LQuadratec ↗Amazon ↗
Holley 550-859 Sniper EFI BBD (258 six)Quadratec ↗Amazon ↗
Hunting a used or discontinued part? Search eBay Motors for Jeep CJ-8 Scrambler parts →
Rated for a competent home mechanic with a decent tool kit. Confirm torque figures, fluids and procedures against the factory service manual for your VIN, support the truck on stands rather than a jack, and work at your own risk (disclaimer). Some parts links are affiliate links, which pay us a small commission at no cost to you.