1. Home
  2. Jeep and Willys (new and old)
  3. 258 wierd idle

258 wierd idle

85 CJ7/258/computer is asleep

A few weeks ago my idle started running rough and the exhaust sounded like at least one cylinder wasn't firing - a rhythmic putt putt putt sound and the exhaust pressure was higher. The weather is finally warm enough to work on this today. I pulled all the plugs to check their condition. 1-4 were nice and tan, 5&6 were a little oily. I reamed the idle tubes well. Stuck it all back together and got no improvement. I started pulling spark wires one by one until the engine ran worse. Much to my surprise, I could pull off #4-6 with no change in idle. with 1-3 off, the engine ran rougher as expected. I rechecked the idle mix screws and the were both at 3.5 turns out

- decided to give 'em another half turn out just to see if it made a difference. The idle is a little better but I still get no change in idle if i pull plug wires 4-6. Any ideas? Am I really running on 3 cylinders? The wires, cap and rotor have about 600 miles on them and all contacts are clean. Any thoughts?

Reply to
KurtS
Loading thread data ...

KurtS did pass the time by typing:

My first thought is your ignition system needs an overhaul. Could be the plug wires, plugs, a crack in the cap or stator, or a carbon trace in the cap.

The oil buildup is proabably due to no spark.

My suggestion is spend a few bucks and replace the plugs/wires/cap/rotor. Look for a cap/rotor that uses brass towers, not aluminum. They last longer and work better. As for the wires, use OEM size and fit. I like Bosh.

Reply to
DougW

I have seen exactly that, recently too.

One of the barrels of the carb is not giving gas at idle.

If the idle tube is clean, then maybe the venturi is clogged up.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

KurtS wrote:

Reply to
Mike Romain

Sounds like the famous "air leaks in the carb" scenario. It isn't that it isn't getting enough gas, the problem is that it is getting too much air. At high vacuum (e.g. idle) the air leaks are upsetting the fuel-air ratio. There are places that will rebuild (MAJOR rebuild) the carb, but you'd probably be way ahead to just replace it with a Weber carb.

Reply to
Ken Finney

OK this is just strange. Since the original bbd carb was giving me so much trouble lately, I bought a new one today. Rebuilt Autozone special -- I know, I know. The choke doesn't work out of the box so it's going back tomorrow. Sigh. Anyway, put the new carb in and while the idle is better (still dialing it in), the same symptoms exist where I can pull any of the plug wires on cyl's 4-6 and the idle doesn't change. Pull any of 1-3 and it stumbles like I would expect. I swapped in known good wires/plugs on 4-6 and it STILL exhibits the same behavior. The cap/rotor are nearly new and in good condition. I know I'm getting good spark on 4-6 - plenty of arc when shorted to the block. Compression is even at 155-160 across all cylinders. WTF is going on here?

Reply to
KurtS

Leaky intake gasket?

Maybe try some carb cleaner spray along the intake gasket to head crack and listen for any idle changes.

Oh and a heads up on that 'new' carb. I have seen 3 'new' carbs that came with pre-plugged up idle tubes and ran as bad if not worse than the ones being replaced.

When the rebuilders get them, they only use chemicals on the clean up. The idle tubes need a physical ream which is a big no no for any rebuilder to do.

Mike

KurtS wrote:

Reply to
Mike Romain

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.