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?

Re: 258 wierd idle
 

KurtS did pass the time by typing:
> 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?

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.

--
DougW

Re: 258 wierd idle
 

KurtS did pass the time by typing:
> 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?

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.

--
DougW

Re: 258 wierd idle
 

KurtS did pass the time by typing:
> 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?

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.

--
DougW

Re: 258 wierd idle
 

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:
>
> 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?

Re: 258 wierd idle
 

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:
>
> 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?

Re: 258 wierd idle
 

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:
>
> 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?

Re: 258 wierd idle
 

"KurtS" <nospam@thanksImFull.spam> wrote in message
news:BC53C2E2.2B02E%nospam@thanksImFull.spam...
> 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?
>

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.

Re: 258 wierd idle
 

"KurtS" <nospam@thanksImFull.spam> wrote in message
news:BC53C2E2.2B02E%nospam@thanksImFull.spam...
> 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?
>

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.

Re: 258 wierd idle
 

"KurtS" <nospam@thanksImFull.spam> wrote in message
news:BC53C2E2.2B02E%nospam@thanksImFull.spam...
> 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?
>

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.