Slightly Rough Running V-8 - '93 JGC

For a long time, I have had a problem of periodic roughness in our '93
JGC V-8. When it occurs, it "seems" like there is a slight loss of
power in the engine at the same time. At other times, the engine runs
smooth as silk and seems to have plenty of power. I have had the
plugs, wires, dist. cap, etc. changed with no real improvement. It's
almost like it is running on 7 cylinders when this happens. At least
that's what it feels like. What else could cause this?

Dick

Dick did pass the time by typing:
> For a long time, I have had a problem of periodic roughness in our '93
> JGC V-8. When it occurs, it "seems" like there is a slight loss of
> power in the engine at the same time. At other times, the engine runs
> smooth as silk and seems to have plenty of power. I have had the
> plugs, wires, dist. cap, etc. changed with no real improvement. It's
> almost like it is running on 7 cylinders when this happens. At least
> that's what it feels like. What else could cause this?

quite a few things, what fault codes does it have?
http://www.revbeergoggles.com/engine_codes.html

A few things to think about:

- how old is your fuel filter?
- how cruddy is the throttle body and the idle air passage?
- how old is your O2 sensor?
- checked the battery terminals and connections?

but first get the codes.


--
-- DougW -- 93 ZJ 4.0 http://members.cox.net/wilsond
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
Banks Header - I can't be broke, I still have BEER in the fridge!

On Sat, 23 Jul 2005 10:18:11 -0500, "DougW"
> wrote:

>Dick did pass the time by typing:
>> For a long time, I have had a problem of periodic roughness in our '93
>> JGC V-8. When it occurs, it "seems" like there is a slight loss of
>> power in the engine at the same time. At other times, the engine runs
>> smooth as silk and seems to have plenty of power. I have had the
>> plugs, wires, dist. cap, etc. changed with no real improvement. It's
>> almost like it is running on 7 cylinders when this happens. At least
>> that's what it feels like. What else could cause this?
>
>quite a few things, what fault codes does it have?
>http://www.revbeergoggles.com/engine_codes.html
>
>A few things to think about:
>
>- how old is your fuel filter?
>- how cruddy is the throttle body and the idle air passage?
>- how old is your O2 sensor?
>- checked the battery terminals and connections?
>
>but first get the codes.

I don't have a scan tool, but the self test codes are 12, 34 and 55.
None seem to be related to problem. Fuel filter was changed at
64,000. O2 sensor is original as far as I can tell from maintenance
records. Battery and terminals are perfect. Don't know about the
throttle body. Injectors were cleaned at 35,000. Jeep has 90,000.

Dick did pass the time by typing:

> I don't have a scan tool, but the self test codes are 12, 34 and 55.

12 - not an issue, just the battery having been off sometime in the last 50 starts

34 - An open or shorted condition detected in the Speed Control vacuum
or vent solenoid circuits. Speed control switch input below the
minimum acceptable voltage.

55 - end of codes

So, 34:

The speed servo uses the common engine ground. So, you could have a problem
with the engine ground strap or the battery to frame ground jumper. Is the hiccup
occuring when you have cruise control on (even the button in even if you haven't
pressed set).

Another thing to look at are the engine mounts. These are for the I6 but the idea
is similar. Shot motor mounts will make the engine run rough (or at least make
it act that way) http://revbeergoggles.com/motormount/


--
DougW

On Sat, 23 Jul 2005 13:29:08 -0500, "DougW"
> wrote:

>Dick did pass the time by typing:
>
>> I don't have a scan tool, but the self test codes are 12, 34 and 55.
>
>12 - not an issue, just the battery having been off sometime in the last 50 starts
>
>34 - An open or shorted condition detected in the Speed Control vacuum
> or vent solenoid circuits. Speed control switch input below the
> minimum acceptable voltage.
>
>55 - end of codes
>
>So, 34:
>
>The speed servo uses the common engine ground. So, you could have a problem
>with the engine ground strap or the battery to frame ground jumper. Is the hiccup
>occuring when you have cruise control on (even the button in even if you haven't
>pressed set).
>
>Another thing to look at are the engine mounts. These are for the I6 but the idea
>is similar. Shot motor mounts will make the engine run rough (or at least make
>it act that way) http://revbeergoggles.com/motormount/

I know the battery ground is good. It was changed recently when a new
battery was put in. I also depend greatly on that connection for my
ham radio installation. Engine and trans mounts were replaced at
82,000 miles. Problem just comes and goes with no apparent
relationship to anything. Doesn't matter if cruise is on or off, but
more noticeable with it off as you have your foot on the throttle.

Dick