help diagnosing a stalling problem
 

ok this is the 88 Sahara 4.2L I mentioned in a couple posts.

It stalls on throttle, if you really step on it from a stop or blip it
fast it will bog, backfire out the carb sometimes, and usually stall. If
you feather it REALLY lightly it will drop RPM's and act like it wants
to stall. If you step down just right though it will rev normally...
Once it's above about 1500 to 2000 RPMs it will rev high with no problem.

Here's what I've done so far. I've hit the whole carb liberally with
carb cleaners, I've pulled vacuum lines checking for leaks, cleaned the
sensor (PCV? plugged into the top front of the valve cover). Cleaned out
a hose that looks just like the one I just mentioned but is plugged into
the top BACK of the valve cover (close to the firewall) and has no
valve... this goes to the back of the air cleaner and has a sort of
filter inside the air cleaner. The filter element looks like it's
supposed to trap Oil but I think it's getting soaked to the point where
it's actually letting oil into the carb (judging from the air filter and
the residue in there).

The only vacuum leak I found was the vacuum timing advance (I think)
which goes from the bottom of the distributor over the valve cover and
under the air cleaner where it Y's into some other vac lines. I pulled
on this and noted a sudden rough idle. For a minute I thought I had my
stall problem. The hose had a tear and pulling it made it lose vacuum.
So I cut it the rest of the way off and attached the slightly shortened
hose back into the Y fitting; idle smoothed back out but it still stalls.

The air cleaner housing has two problems. There's a plate in the intake
which is above an inlet coming from the exhaust manifold (exhaust gas
recirculation?), this plate is attached via wire to a diaphragm on the
outside top of the intake, which has a functional vacuum line attached.
the diaphragm is lose (no longer riveted) and doesn't seem to be doing
it's job. Right behind this (closer to where the air cleaner housing
meets the intake) also on top is another diaphragm (same look) this has
a U shaped attachment that is no longer attached to a little plastic
lever which appears broken inside (looks like there might have been a
plastic plate attached to it). This is also attached to another vac line
this vac line when removed doesn't suck air. If anyone wants to take a
moment (or three) and fill me in on what these do and what they're
called I'd appreciate it. Hard to replace something when you don't even
know what it's called.

I haven't messed with a Carb since I was a teenager, and I've never
messed with one that has all cludgy sensor/EPA stuff. Any thoughts on
what the problem might be greatly appreciated. Even if I don't buy the
Jeep I'd like to fix this problem.

Re: help diagnosing a stalling problem
 

*Something* is causing it to lean out when you open the butterflies.
Sounds like a bad accelerator pump to me.

"Simon Juncal" <sjuncal@erols.com> wrote in message
news:3F332012.7020801@erols.com...
> ok this is the 88 Sahara 4.2L I mentioned in a couple posts.
>
> It stalls on throttle, if you really step on it from a stop or blip it
> fast it will bog, backfire out the carb sometimes, and usually stall. If
> you feather it REALLY lightly it will drop RPM's and act like it wants
> to stall. If you step down just right though it will rev normally...
> Once it's above about 1500 to 2000 RPMs it will rev high with no problem.
>
> Here's what I've done so far. I've hit the whole carb liberally with
> carb cleaners, I've pulled vacuum lines checking for leaks, cleaned the
> sensor (PCV? plugged into the top front of the valve cover). Cleaned out
> a hose that looks just like the one I just mentioned but is plugged into
> the top BACK of the valve cover (close to the firewall) and has no
> valve... this goes to the back of the air cleaner and has a sort of
> filter inside the air cleaner. The filter element looks like it's
> supposed to trap Oil but I think it's getting soaked to the point where
> it's actually letting oil into the carb (judging from the air filter and
> the residue in there).
>
> The only vacuum leak I found was the vacuum timing advance (I think)
> which goes from the bottom of the distributor over the valve cover and
> under the air cleaner where it Y's into some other vac lines. I pulled
> on this and noted a sudden rough idle. For a minute I thought I had my
> stall problem. The hose had a tear and pulling it made it lose vacuum.
> So I cut it the rest of the way off and attached the slightly shortened
> hose back into the Y fitting; idle smoothed back out but it still stalls.
>
> The air cleaner housing has two problems. There's a plate in the intake
> which is above an inlet coming from the exhaust manifold (exhaust gas
> recirculation?), this plate is attached via wire to a diaphragm on the
> outside top of the intake, which has a functional vacuum line attached.
> the diaphragm is lose (no longer riveted) and doesn't seem to be doing
> it's job. Right behind this (closer to where the air cleaner housing
> meets the intake) also on top is another diaphragm (same look) this has
> a U shaped attachment that is no longer attached to a little plastic
> lever which appears broken inside (looks like there might have been a
> plastic plate attached to it). This is also attached to another vac line
> this vac line when removed doesn't suck air. If anyone wants to take a
> moment (or three) and fill me in on what these do and what they're
> called I'd appreciate it. Hard to replace something when you don't even
> know what it's called.
>
> I haven't messed with a Carb since I was a teenager, and I've never
> messed with one that has all cludgy sensor/EPA stuff. Any thoughts on
> what the problem might be greatly appreciated. Even if I don't buy the
> Jeep I'd like to fix this problem.
>

Re: help diagnosing a stalling problem
 

Ok....

Man are you 'really' sure you want to tackle this 'before' you buy it?

I wouldn't recommend it....

I bought my Jeep cheap because of the same type of symptoms this one
shows and the previous owner was convinced it needed a new engine
because of all the oil blow by in the air filter and carb.

It is a badly messed up emissions system that 'could' just need elbow
grease, but more likely needs a new charcoal canister which is about
$160.00 and it 'for sure' needs a carb kit which is only $20.00 and a
few hours to instal.

The air filter is broken, that can be bypassed at the expense of good
cold running and an iced up carb or can be fixed likely with some
creative use of sheet metal screws and some coat hangers. Or find
someone that has gone K+N and has an old air box laying around.

A working air filter box is needed for emissions.

I can walk you through it if you really want to tackle it....

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

Simon Juncal wrote:
>
> ok this is the 88 Sahara 4.2L I mentioned in a couple posts.
>
> It stalls on throttle, if you really step on it from a stop or blip it
> fast it will bog, backfire out the carb sometimes, and usually stall. If
> you feather it REALLY lightly it will drop RPM's and act like it wants
> to stall. If you step down just right though it will rev normally...
> Once it's above about 1500 to 2000 RPMs it will rev high with no problem.
>
> Here's what I've done so far. I've hit the whole carb liberally with
> carb cleaners, I've pulled vacuum lines checking for leaks, cleaned the
> sensor (PCV? plugged into the top front of the valve cover). Cleaned out
> a hose that looks just like the one I just mentioned but is plugged into
> the top BACK of the valve cover (close to the firewall) and has no
> valve... this goes to the back of the air cleaner and has a sort of
> filter inside the air cleaner. The filter element looks like it's
> supposed to trap Oil but I think it's getting soaked to the point where
> it's actually letting oil into the carb (judging from the air filter and
> the residue in there).
>
> The only vacuum leak I found was the vacuum timing advance (I think)
> which goes from the bottom of the distributor over the valve cover and
> under the air cleaner where it Y's into some other vac lines. I pulled
> on this and noted a sudden rough idle. For a minute I thought I had my
> stall problem. The hose had a tear and pulling it made it lose vacuum.
> So I cut it the rest of the way off and attached the slightly shortened
> hose back into the Y fitting; idle smoothed back out but it still stalls.
>
> The air cleaner housing has two problems. There's a plate in the intake
> which is above an inlet coming from the exhaust manifold (exhaust gas
> recirculation?), this plate is attached via wire to a diaphragm on the
> outside top of the intake, which has a functional vacuum line attached.
> the diaphragm is lose (no longer riveted) and doesn't seem to be doing
> it's job. Right behind this (closer to where the air cleaner housing
> meets the intake) also on top is another diaphragm (same look) this has
> a U shaped attachment that is no longer attached to a little plastic
> lever which appears broken inside (looks like there might have been a
> plastic plate attached to it). This is also attached to another vac line
> this vac line when removed doesn't suck air. If anyone wants to take a
> moment (or three) and fill me in on what these do and what they're
> called I'd appreciate it. Hard to replace something when you don't even
> know what it's called.
>
> I haven't messed with a Carb since I was a teenager, and I've never
> messed with one that has all cludgy sensor/EPA stuff. Any thoughts on
> what the problem might be greatly appreciated. Even if I don't buy the
> Jeep I'd like to fix this problem.