I posted before about a cold start rough idle that I thought was maybe
the choke. The choke kicks in (snaps shut when opening the throttle) and
the fast idle cam is doing it's job. It also opens up as it warms.

Here's the symptoms: I pump the gas enough to get her to fire (about
four pumps) it fires up and idles smoothly for about 7 or 8 seconds and
then gets rough, stumbling like it wants to stall, if I leave it alone
it will stall OR the RPM's will raise and everything smoothes out and
idles at the fast idle screw setting (a little over 1500 RPM's
currently). Higher fast idle settings (2000 rpm's) seem to make the
stumble worse and for little longer (more likely to stall than smooth out).

While it was stumbling the other day I went around and noticed black
puffs from the tail pipe... Which cleared to steam when the idle
smoothed out. I think the stepper motor is enriching the mix too much
for that short period of time after the initial start and backs the mix
back to normal (whatever that happens to be) at which point the fast
idle setting can get the RPM's to the level I've set them at.

So what sensor might cause the stepper to go too rich? I just tuned it
up which didn't fix the problem. I changed the plugs (all carbonized
with some light brown/tan spots, but no fouling) cap and rotor, new
wires. There's a small amount of blow by (the little square fiber filter
inside the air filter housing has some oil and a bit of residue on the
cover at the same spot).

88 YJ with 4.2 and Cater POS.

--
Simon
"I may be wrong, but I'm not uncertain." -- Robert A. Heinlein

 

Simon, for what it is worth...have a 258, 4.2L, here, (1975) and have found
out over the years that the bolts holding the manifolds (intake/exhust), must
be retorgued, about twice a year, seems to cure a lot of problems...do not
forget the 2 bolts that hold the exhust pipe to the manifold...Gene...

 

Simon, for what it is worth...have a 258, 4.2L, here, (1975) and have found
out over the years that the bolts holding the manifolds (intake/exhust), must
be retorgued, about twice a year, seems to cure a lot of problems...do not
forget the 2 bolts that hold the exhust pipe to the manifold...Gene...

 

Simon, for what it is worth...have a 258, 4.2L, here, (1975) and have found
out over the years that the bolts holding the manifolds (intake/exhust), must
be retorgued, about twice a year, seems to cure a lot of problems...do not
forget the 2 bolts that hold the exhust pipe to the manifold...Gene...

 

I'm a noobie when it comes to carbs but it sounds like your choke pull
off is not pulling the choke open, once you start to get combustion
the carb should create the vacuum to pull on the pull off diaphram and
open the choke
You could also have too much tension on the electric choke IE: it is
turned to far to towards the front of the engine, try taking the choke
setting back to notches toward the firewall.

I had similar problems a few weeks ago I did some tinkering with the
choke and mine fires up so smooth now you would think it was a new
vehicle. But of course my plugs are seeing a hell of a lot more spark
with the HEI distributor that I put in..... this or the TFI
distributor mod I highly recommend.

Does it idle smooth once warmed up?


On Thu, 25 Dec 2003 11:17:55 -0500, Simon Juncal <sjuncal@erols.com>
wrote:

>I posted before about a cold start rough idle that I thought was maybe
>the choke. The choke kicks in (snaps shut when opening the throttle) and
>the fast idle cam is doing it's job. It also opens up as it warms.
>
>Here's the symptoms: I pump the gas enough to get her to fire (about
>four pumps) it fires up and idles smoothly for about 7 or 8 seconds and
>then gets rough, stumbling like it wants to stall, if I leave it alone
>it will stall OR the RPM's will raise and everything smoothes out and
>idles at the fast idle screw setting (a little over 1500 RPM's
>currently). Higher fast idle settings (2000 rpm's) seem to make the
>stumble worse and for little longer (more likely to stall than smooth out).
>
>While it was stumbling the other day I went around and noticed black
>puffs from the tail pipe... Which cleared to steam when the idle
>smoothed out. I think the stepper motor is enriching the mix too much
>for that short period of time after the initial start and backs the mix
>back to normal (whatever that happens to be) at which point the fast
>idle setting can get the RPM's to the level I've set them at.
>
>So what sensor might cause the stepper to go too rich? I just tuned it
>up which didn't fix the problem. I changed the plugs (all carbonized
>with some light brown/tan spots, but no fouling) cap and rotor, new
>wires. There's a small amount of blow by (the little square fiber filter
>inside the air filter housing has some oil and a bit of residue on the
>cover at the same spot).
>
>88 YJ with 4.2 and Cater POS.

 

I'm a noobie when it comes to carbs but it sounds like your choke pull
off is not pulling the choke open, once you start to get combustion
the carb should create the vacuum to pull on the pull off diaphram and
open the choke
You could also have too much tension on the electric choke IE: it is
turned to far to towards the front of the engine, try taking the choke
setting back to notches toward the firewall.

I had similar problems a few weeks ago I did some tinkering with the
choke and mine fires up so smooth now you would think it was a new
vehicle. But of course my plugs are seeing a hell of a lot more spark
with the HEI distributor that I put in..... this or the TFI
distributor mod I highly recommend.

Does it idle smooth once warmed up?


On Thu, 25 Dec 2003 11:17:55 -0500, Simon Juncal <sjuncal@erols.com>
wrote:

>I posted before about a cold start rough idle that I thought was maybe
>the choke. The choke kicks in (snaps shut when opening the throttle) and
>the fast idle cam is doing it's job. It also opens up as it warms.
>
>Here's the symptoms: I pump the gas enough to get her to fire (about
>four pumps) it fires up and idles smoothly for about 7 or 8 seconds and
>then gets rough, stumbling like it wants to stall, if I leave it alone
>it will stall OR the RPM's will raise and everything smoothes out and
>idles at the fast idle screw setting (a little over 1500 RPM's
>currently). Higher fast idle settings (2000 rpm's) seem to make the
>stumble worse and for little longer (more likely to stall than smooth out).
>
>While it was stumbling the other day I went around and noticed black
>puffs from the tail pipe... Which cleared to steam when the idle
>smoothed out. I think the stepper motor is enriching the mix too much
>for that short period of time after the initial start and backs the mix
>back to normal (whatever that happens to be) at which point the fast
>idle setting can get the RPM's to the level I've set them at.
>
>So what sensor might cause the stepper to go too rich? I just tuned it
>up which didn't fix the problem. I changed the plugs (all carbonized
>with some light brown/tan spots, but no fouling) cap and rotor, new
>wires. There's a small amount of blow by (the little square fiber filter
>inside the air filter housing has some oil and a bit of residue on the
>cover at the same spot).
>
>88 YJ with 4.2 and Cater POS.

 

I'm a noobie when it comes to carbs but it sounds like your choke pull
off is not pulling the choke open, once you start to get combustion
the carb should create the vacuum to pull on the pull off diaphram and
open the choke
You could also have too much tension on the electric choke IE: it is
turned to far to towards the front of the engine, try taking the choke
setting back to notches toward the firewall.

I had similar problems a few weeks ago I did some tinkering with the
choke and mine fires up so smooth now you would think it was a new
vehicle. But of course my plugs are seeing a hell of a lot more spark
with the HEI distributor that I put in..... this or the TFI
distributor mod I highly recommend.

Does it idle smooth once warmed up?


On Thu, 25 Dec 2003 11:17:55 -0500, Simon Juncal <sjuncal@erols.com>
wrote:

>I posted before about a cold start rough idle that I thought was maybe
>the choke. The choke kicks in (snaps shut when opening the throttle) and
>the fast idle cam is doing it's job. It also opens up as it warms.
>
>Here's the symptoms: I pump the gas enough to get her to fire (about
>four pumps) it fires up and idles smoothly for about 7 or 8 seconds and
>then gets rough, stumbling like it wants to stall, if I leave it alone
>it will stall OR the RPM's will raise and everything smoothes out and
>idles at the fast idle screw setting (a little over 1500 RPM's
>currently). Higher fast idle settings (2000 rpm's) seem to make the
>stumble worse and for little longer (more likely to stall than smooth out).
>
>While it was stumbling the other day I went around and noticed black
>puffs from the tail pipe... Which cleared to steam when the idle
>smoothed out. I think the stepper motor is enriching the mix too much
>for that short period of time after the initial start and backs the mix
>back to normal (whatever that happens to be) at which point the fast
>idle setting can get the RPM's to the level I've set them at.
>
>So what sensor might cause the stepper to go too rich? I just tuned it
>up which didn't fix the problem. I changed the plugs (all carbonized
>with some light brown/tan spots, but no fouling) cap and rotor, new
>wires. There's a small amount of blow by (the little square fiber filter
>inside the air filter housing has some oil and a bit of residue on the
>cover at the same spot).
>
>88 YJ with 4.2 and Cater POS.

 

Sounds like you might have the choke set up a little too rich.

The cover on the choke is adjustable and has notches on it for rich and
lean.

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

Simon Juncal wrote:
>
> I posted before about a cold start rough idle that I thought was maybe
> the choke. The choke kicks in (snaps shut when opening the throttle) and
> the fast idle cam is doing it's job. It also opens up as it warms.
>
> Here's the symptoms: I pump the gas enough to get her to fire (about
> four pumps) it fires up and idles smoothly for about 7 or 8 seconds and
> then gets rough, stumbling like it wants to stall, if I leave it alone
> it will stall OR the RPM's will raise and everything smoothes out and
> idles at the fast idle screw setting (a little over 1500 RPM's
> currently). Higher fast idle settings (2000 rpm's) seem to make the
> stumble worse and for little longer (more likely to stall than smooth out).
>
> While it was stumbling the other day I went around and noticed black
> puffs from the tail pipe... Which cleared to steam when the idle
> smoothed out. I think the stepper motor is enriching the mix too much
> for that short period of time after the initial start and backs the mix
> back to normal (whatever that happens to be) at which point the fast
> idle setting can get the RPM's to the level I've set them at.
>
> So what sensor might cause the stepper to go too rich? I just tuned it
> up which didn't fix the problem. I changed the plugs (all carbonized
> with some light brown/tan spots, but no fouling) cap and rotor, new
> wires. There's a small amount of blow by (the little square fiber filter
> inside the air filter housing has some oil and a bit of residue on the
> cover at the same spot).
>
> 88 YJ with 4.2 and Cater POS.
>
> --
> Simon
> "I may be wrong, but I'm not uncertain." -- Robert A. Heinlein

 

Sounds like you might have the choke set up a little too rich.

The cover on the choke is adjustable and has notches on it for rich and
lean.

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

Simon Juncal wrote:
>
> I posted before about a cold start rough idle that I thought was maybe
> the choke. The choke kicks in (snaps shut when opening the throttle) and
> the fast idle cam is doing it's job. It also opens up as it warms.
>
> Here's the symptoms: I pump the gas enough to get her to fire (about
> four pumps) it fires up and idles smoothly for about 7 or 8 seconds and
> then gets rough, stumbling like it wants to stall, if I leave it alone
> it will stall OR the RPM's will raise and everything smoothes out and
> idles at the fast idle screw setting (a little over 1500 RPM's
> currently). Higher fast idle settings (2000 rpm's) seem to make the
> stumble worse and for little longer (more likely to stall than smooth out).
>
> While it was stumbling the other day I went around and noticed black
> puffs from the tail pipe... Which cleared to steam when the idle
> smoothed out. I think the stepper motor is enriching the mix too much
> for that short period of time after the initial start and backs the mix
> back to normal (whatever that happens to be) at which point the fast
> idle setting can get the RPM's to the level I've set them at.
>
> So what sensor might cause the stepper to go too rich? I just tuned it
> up which didn't fix the problem. I changed the plugs (all carbonized
> with some light brown/tan spots, but no fouling) cap and rotor, new
> wires. There's a small amount of blow by (the little square fiber filter
> inside the air filter housing has some oil and a bit of residue on the
> cover at the same spot).
>
> 88 YJ with 4.2 and Cater POS.
>
> --
> Simon
> "I may be wrong, but I'm not uncertain." -- Robert A. Heinlein

 

Sounds like you might have the choke set up a little too rich.

The cover on the choke is adjustable and has notches on it for rich and
lean.

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

Simon Juncal wrote:
>
> I posted before about a cold start rough idle that I thought was maybe
> the choke. The choke kicks in (snaps shut when opening the throttle) and
> the fast idle cam is doing it's job. It also opens up as it warms.
>
> Here's the symptoms: I pump the gas enough to get her to fire (about
> four pumps) it fires up and idles smoothly for about 7 or 8 seconds and
> then gets rough, stumbling like it wants to stall, if I leave it alone
> it will stall OR the RPM's will raise and everything smoothes out and
> idles at the fast idle screw setting (a little over 1500 RPM's
> currently). Higher fast idle settings (2000 rpm's) seem to make the
> stumble worse and for little longer (more likely to stall than smooth out).
>
> While it was stumbling the other day I went around and noticed black
> puffs from the tail pipe... Which cleared to steam when the idle
> smoothed out. I think the stepper motor is enriching the mix too much
> for that short period of time after the initial start and backs the mix
> back to normal (whatever that happens to be) at which point the fast
> idle setting can get the RPM's to the level I've set them at.
>
> So what sensor might cause the stepper to go too rich? I just tuned it
> up which didn't fix the problem. I changed the plugs (all carbonized
> with some light brown/tan spots, but no fouling) cap and rotor, new
> wires. There's a small amount of blow by (the little square fiber filter
> inside the air filter housing has some oil and a bit of residue on the
> cover at the same spot).
>
> 88 YJ with 4.2 and Cater POS.
>
> --
> Simon
> "I may be wrong, but I'm not uncertain." -- Robert A. Heinlein