Idle and timing issues
 

Thought I would check my ignition timing on the 1990 256 YJ. Checking at
700 rpm showed only about 3 degrees advanced. I advanced it to 9
degrees. I had to back the idle screw almost all the way out to get it
back to 700 rpm. The strange thing is that now after letting off the
gas, the idle is very rough and about 300-400 rpm higher. After a
varying amount of time 5 to 20 seconds, the idle drops to about 700 and
smooths out. When the idle smooths out and drops to where it should be,
there is a click somewhere on top of the engine. My guess is that it is
a solenoid. Anyone know what the computer might be doing after coming
back from high rpm to curb idle. It doesn't seem to be the sol-vac that
is doing it.

The good news is that the Jeep is way more responsive and has never run
better. If I could just get rid of the rough faster idle period I would
be a happy camper.

I have checked several times for a vacuum leak and so far no luck.

Also I am somewhat confused about the procedure for timing adjustment in
my Haynes book It says to disconnect the electrical connector from the
CEC sys switch located on top of the valve cover. What is this? It also
says to increase the idle speed to 1600 rpm and the the timing mark
should appear stationary. Does this mean that there should be no advance
between spec idle at 700 rpm and 1600 rpm? It seems there was some
advance on mine as you went to 1700 rpm, which I attributed to the a
centrifugal advance. When I checked and reset the timing, I only
disconnected the vac advance, but not the CEC system switch since I
could not find out what that was.

Guess I am missing something here.

Aloha from Maui
Joe

Re: Idle and timing issues
 

The book way is for the computer run carb 258 engine. At 1600 rpm, your
mechanical timing is full advance and then the computer takes over. I
believe the distributor vacuum line should be off and plugged too.

My guess is that click you hear shutting off the vacuum leak (high idle)
is the defective PCV/canister solenoid that sits just behind the carb.
These never did work, so the fix is to pull it and just put a plain T
fitting in it's place.

My CJ7 with no computer messing up the works runs best at about 7-9 deg
advance at 700 rpm with a ported vacuum signal. But, when I killed the
computer, my timing had to be advanced by about 10 degrees to run
manually.

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

Joe and Joann wrote:
>
> Thought I would check my ignition timing on the 1990 256 YJ. Checking at
> 700 rpm showed only about 3 degrees advanced. I advanced it to 9
> degrees. I had to back the idle screw almost all the way out to get it
> back to 700 rpm. The strange thing is that now after letting off the
> gas, the idle is very rough and about 300-400 rpm higher. After a
> varying amount of time 5 to 20 seconds, the idle drops to about 700 and
> smooths out. When the idle smooths out and drops to where it should be,
> there is a click somewhere on top of the engine. My guess is that it is
> a solenoid. Anyone know what the computer might be doing after coming
> back from high rpm to curb idle. It doesn't seem to be the sol-vac that
> is doing it.
>
> The good news is that the Jeep is way more responsive and has never run
> better. If I could just get rid of the rough faster idle period I would
> be a happy camper.
>
> I have checked several times for a vacuum leak and so far no luck.
>
> Also I am somewhat confused about the procedure for timing adjustment in
> my Haynes book It says to disconnect the electrical connector from the
> CEC sys switch located on top of the valve cover. What is this? It also
> says to increase the idle speed to 1600 rpm and the the timing mark
> should appear stationary. Does this mean that there should be no advance
> between spec idle at 700 rpm and 1600 rpm? It seems there was some
> advance on mine as you went to 1700 rpm, which I attributed to the a
> centrifugal advance. When I checked and reset the timing, I only
> disconnected the vac advance, but not the CEC system switch since I
> could not find out what that was.
>
> Guess I am missing something here.
>
> Aloha from Maui
> Joe

Re: Idle and timing issues
 

The book way is for the computer run carb 258 engine. At 1600 rpm, your
mechanical timing is full advance and then the computer takes over. I
believe the distributor vacuum line should be off and plugged too.

My guess is that click you hear shutting off the vacuum leak (high idle)
is the defective PCV/canister solenoid that sits just behind the carb.
These never did work, so the fix is to pull it and just put a plain T
fitting in it's place.

My CJ7 with no computer messing up the works runs best at about 7-9 deg
advance at 700 rpm with a ported vacuum signal. But, when I killed the
computer, my timing had to be advanced by about 10 degrees to run
manually.

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

Joe and Joann wrote:
>
> Thought I would check my ignition timing on the 1990 256 YJ. Checking at
> 700 rpm showed only about 3 degrees advanced. I advanced it to 9
> degrees. I had to back the idle screw almost all the way out to get it
> back to 700 rpm. The strange thing is that now after letting off the
> gas, the idle is very rough and about 300-400 rpm higher. After a
> varying amount of time 5 to 20 seconds, the idle drops to about 700 and
> smooths out. When the idle smooths out and drops to where it should be,
> there is a click somewhere on top of the engine. My guess is that it is
> a solenoid. Anyone know what the computer might be doing after coming
> back from high rpm to curb idle. It doesn't seem to be the sol-vac that
> is doing it.
>
> The good news is that the Jeep is way more responsive and has never run
> better. If I could just get rid of the rough faster idle period I would
> be a happy camper.
>
> I have checked several times for a vacuum leak and so far no luck.
>
> Also I am somewhat confused about the procedure for timing adjustment in
> my Haynes book It says to disconnect the electrical connector from the
> CEC sys switch located on top of the valve cover. What is this? It also
> says to increase the idle speed to 1600 rpm and the the timing mark
> should appear stationary. Does this mean that there should be no advance
> between spec idle at 700 rpm and 1600 rpm? It seems there was some
> advance on mine as you went to 1700 rpm, which I attributed to the a
> centrifugal advance. When I checked and reset the timing, I only
> disconnected the vac advance, but not the CEC system switch since I
> could not find out what that was.
>
> Guess I am missing something here.
>
> Aloha from Maui
> Joe

Re: Idle and timing issues
 

The book way is for the computer run carb 258 engine. At 1600 rpm, your
mechanical timing is full advance and then the computer takes over. I
believe the distributor vacuum line should be off and plugged too.

My guess is that click you hear shutting off the vacuum leak (high idle)
is the defective PCV/canister solenoid that sits just behind the carb.
These never did work, so the fix is to pull it and just put a plain T
fitting in it's place.

My CJ7 with no computer messing up the works runs best at about 7-9 deg
advance at 700 rpm with a ported vacuum signal. But, when I killed the
computer, my timing had to be advanced by about 10 degrees to run
manually.

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

Joe and Joann wrote:
>
> Thought I would check my ignition timing on the 1990 256 YJ. Checking at
> 700 rpm showed only about 3 degrees advanced. I advanced it to 9
> degrees. I had to back the idle screw almost all the way out to get it
> back to 700 rpm. The strange thing is that now after letting off the
> gas, the idle is very rough and about 300-400 rpm higher. After a
> varying amount of time 5 to 20 seconds, the idle drops to about 700 and
> smooths out. When the idle smooths out and drops to where it should be,
> there is a click somewhere on top of the engine. My guess is that it is
> a solenoid. Anyone know what the computer might be doing after coming
> back from high rpm to curb idle. It doesn't seem to be the sol-vac that
> is doing it.
>
> The good news is that the Jeep is way more responsive and has never run
> better. If I could just get rid of the rough faster idle period I would
> be a happy camper.
>
> I have checked several times for a vacuum leak and so far no luck.
>
> Also I am somewhat confused about the procedure for timing adjustment in
> my Haynes book It says to disconnect the electrical connector from the
> CEC sys switch located on top of the valve cover. What is this? It also
> says to increase the idle speed to 1600 rpm and the the timing mark
> should appear stationary. Does this mean that there should be no advance
> between spec idle at 700 rpm and 1600 rpm? It seems there was some
> advance on mine as you went to 1700 rpm, which I attributed to the a
> centrifugal advance. When I checked and reset the timing, I only
> disconnected the vac advance, but not the CEC system switch since I
> could not find out what that was.
>
> Guess I am missing something here.
>
> Aloha from Maui
> Joe

Re: Idle and timing issues
 

The book way is for the computer run carb 258 engine. At 1600 rpm, your
mechanical timing is full advance and then the computer takes over. I
believe the distributor vacuum line should be off and plugged too.

My guess is that click you hear shutting off the vacuum leak (high idle)
is the defective PCV/canister solenoid that sits just behind the carb.
These never did work, so the fix is to pull it and just put a plain T
fitting in it's place.

My CJ7 with no computer messing up the works runs best at about 7-9 deg
advance at 700 rpm with a ported vacuum signal. But, when I killed the
computer, my timing had to be advanced by about 10 degrees to run
manually.

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

Joe and Joann wrote:
>
> Thought I would check my ignition timing on the 1990 256 YJ. Checking at
> 700 rpm showed only about 3 degrees advanced. I advanced it to 9
> degrees. I had to back the idle screw almost all the way out to get it
> back to 700 rpm. The strange thing is that now after letting off the
> gas, the idle is very rough and about 300-400 rpm higher. After a
> varying amount of time 5 to 20 seconds, the idle drops to about 700 and
> smooths out. When the idle smooths out and drops to where it should be,
> there is a click somewhere on top of the engine. My guess is that it is
> a solenoid. Anyone know what the computer might be doing after coming
> back from high rpm to curb idle. It doesn't seem to be the sol-vac that
> is doing it.
>
> The good news is that the Jeep is way more responsive and has never run
> better. If I could just get rid of the rough faster idle period I would
> be a happy camper.
>
> I have checked several times for a vacuum leak and so far no luck.
>
> Also I am somewhat confused about the procedure for timing adjustment in
> my Haynes book It says to disconnect the electrical connector from the
> CEC sys switch located on top of the valve cover. What is this? It also
> says to increase the idle speed to 1600 rpm and the the timing mark
> should appear stationary. Does this mean that there should be no advance
> between spec idle at 700 rpm and 1600 rpm? It seems there was some
> advance on mine as you went to 1700 rpm, which I attributed to the a
> centrifugal advance. When I checked and reset the timing, I only
> disconnected the vac advance, but not the CEC system switch since I
> could not find out what that was.
>
> Guess I am missing something here.
>
> Aloha from Maui
> Joe

Re: Idle and timing issues
 

Thanks Mike, but I am still confused about the 1600 rpm. With the
vacuum advance disconnected and plugged, is there a mechanical advance
that happens between 700 and 1600. In any event, assuming I disconnect
and plug the vacuum advance, do I set 9 degrees BTDC at 700 or 1600 rpm?



Mike Romain wrote:
> The book way is for the computer run carb 258 engine. At 1600 rpm, your
> mechanical timing is full advance and then the computer takes over. I
> believe the distributor vacuum line should be off and plugged too.

snip

Re: Idle and timing issues
 

Thanks Mike, but I am still confused about the 1600 rpm. With the
vacuum advance disconnected and plugged, is there a mechanical advance
that happens between 700 and 1600. In any event, assuming I disconnect
and plug the vacuum advance, do I set 9 degrees BTDC at 700 or 1600 rpm?



Mike Romain wrote:
> The book way is for the computer run carb 258 engine. At 1600 rpm, your
> mechanical timing is full advance and then the computer takes over. I
> believe the distributor vacuum line should be off and plugged too.

snip

Re: Idle and timing issues
 

Thanks Mike, but I am still confused about the 1600 rpm. With the
vacuum advance disconnected and plugged, is there a mechanical advance
that happens between 700 and 1600. In any event, assuming I disconnect
and plug the vacuum advance, do I set 9 degrees BTDC at 700 or 1600 rpm?



Mike Romain wrote:
> The book way is for the computer run carb 258 engine. At 1600 rpm, your
> mechanical timing is full advance and then the computer takes over. I
> believe the distributor vacuum line should be off and plugged too.

snip

Re: Idle and timing issues
 

Thanks Mike, but I am still confused about the 1600 rpm. With the
vacuum advance disconnected and plugged, is there a mechanical advance
that happens between 700 and 1600. In any event, assuming I disconnect
and plug the vacuum advance, do I set 9 degrees BTDC at 700 or 1600 rpm?



Mike Romain wrote:
> The book way is for the computer run carb 258 engine. At 1600 rpm, your
> mechanical timing is full advance and then the computer takes over. I
> believe the distributor vacuum line should be off and plugged too.

snip

Re: Idle and timing issues
 

The distributor has a mechanical advance on springs and weights that
maxes out at just under 1600 rpm from what I understand, then the
computer takes over so the base timing is way down. No computer and set
the timing at idle at 7-9 deg with vacuum off, whichever sounds
smoothest, otherwise go by the hood sticker or book at 1600. You can
play there by a degree or two to to get the smoothest idle.

You are supposed to oil the felt pad in the center of the distributor
under the rotor every time you change the cap and rotor. If you open it
up and grab the rotor, it will turn under a spring load or it needs
cleaning and oiling if it's grabby.

Mike

Joe and Joann wrote:
>
> Thanks Mike, but I am still confused about the 1600 rpm. With the
> vacuum advance disconnected and plugged, is there a mechanical advance
> that happens between 700 and 1600. In any event, assuming I disconnect
> and plug the vacuum advance, do I set 9 degrees BTDC at 700 or 1600 rpm?
>
> Mike Romain wrote:
> > The book way is for the computer run carb 258 engine. At 1600 rpm, your
> > mechanical timing is full advance and then the computer takes over. I
> > believe the distributor vacuum line should be off and plugged too.
>
> snip