XJ stumble, check engine light

This is the second time this has happened, otherwise the Jeep runs
great. Once at about 15k miles and this time at about 50k miles, upon
cold starting, the engine stumbles (of course no gas pedal), runs really
rough for about 20-30 seconds, then planes out. This triggers the CHECK
ENGINE light. The vehicle runs fine after that, but the light stays on.
The first time, the dealer reset the light during a visit for a brake
rotor issue, but found no problems. Gas cap OK, both times. Suggestions?

tw
--
__________________________________________________ ___________________
2003 TJ Rubicon * 2001 XJ Sport * 1971 Bill Stroppe Baja Bronco

"There is a very fine line between 'hobby' and 'mental illness'."

Pronunciation: 'jEp Function: noun Date: 1940

Etymology: from g. p. (G= 'Government' P= '80 inch wheelbase')
A small general-purpose motor vehicle with 80" wheelbase, 1/4-ton
capacity and four-wheel drive used by the U.S. army in World War II.
__________________________________________________ ___________________

What code?

"twaldron" > wrote in message
m...
> This is the second time this has happened, otherwise the Jeep runs
> great. Once at about 15k miles and this time at about 50k miles, upon
> cold starting, the engine stumbles (of course no gas pedal), runs really
> rough for about 20-30 seconds, then planes out. This triggers the CHECK
> ENGINE light. The vehicle runs fine after that, but the light stays on.
> The first time, the dealer reset the light during a visit for a brake
> rotor issue, but found no problems. Gas cap OK, both times. Suggestions?
>
> tw
> --
> __________________________________________________ ___________________
> 2003 TJ Rubicon * 2001 XJ Sport * 1971 Bill Stroppe Baja Bronco
>
> "There is a very fine line between 'hobby' and 'mental illness'."
>
> Pronunciation: 'jEp Function: noun Date: 1940
>
> Etymology: from g. p. (G= 'Government' P= '80 inch wheelbase')
> A small general-purpose motor vehicle with 80" wheelbase, 1/4-ton
> capacity and four-wheel drive used by the U.S. army in World War II.
> __________________________________________________ ___________________

I haven't had the error checked this time for a code, but the problem is
exactly like last time. I'm pretty sure the code was P0300 last time.

tw
__________________________________________________ ___________________
2003 TJ Rubicon * 2001 XJ Sport * 1971 Bill Stroppe Baja Bronco

"There is a very fine line between 'hobby' and 'mental illness'."

Pronunciation: 'jEp Function: noun Date: 1940

Etymology: from g. p. (G= 'Government' P= '80 inch wheelbase')
A small general-purpose motor vehicle with 80" wheelbase, 1/4-ton
capacity and four-wheel drive used by the U.S. army in World War II.
__________________________________________________ ___________________


Billy Ray wrote:
> What code?
>
> "twaldron" > wrote in message
> m...
>
>>This is the second time this has happened, otherwise the Jeep runs
>>great. Once at about 15k miles and this time at about 50k miles, upon
>>cold starting, the engine stumbles (of course no gas pedal), runs really
>>rough for about 20-30 seconds, then planes out. This triggers the CHECK
>>ENGINE light. The vehicle runs fine after that, but the light stays on.
>>The first time, the dealer reset the light during a visit for a brake
>>rotor issue, but found no problems. Gas cap OK, both times. Suggestions?
>>
>>tw
>>--
>>________________________________________________ _____________________
>>2003 TJ Rubicon * 2001 XJ Sport * 1971 Bill Stroppe Baja Bronco
>>
>>"There is a very fine line between 'hobby' and 'mental illness'."
>>
>>Pronunciation: 'jEp Function: noun Date: 1940
>>
>>Etymology: from g. p. (G= 'Government' P= '80 inch wheelbase')
>>A small general-purpose motor vehicle with 80" wheelbase, 1/4-ton
>>capacity and four-wheel drive used by the U.S. army in World War II.
>>________________________________________________ _____________________
>
>
>

Yes, it would. I don't have a reader, so I'm looking to try a few common
things prior to paying for a service visit.

tw
__________________________________________________ ___________________
2003 TJ Rubicon * 2001 XJ Sport * 1971 Bill Stroppe Baja Bronco

"There is a very fine line between 'hobby' and 'mental illness'."

Pronunciation: 'jEp Function: noun Date: 1940

Etymology: from g. p. (G= 'Government' P= '80 inch wheelbase')
A small general-purpose motor vehicle with 80" wheelbase, 1/4-ton
capacity and four-wheel drive used by the U.S. army in World War II.
__________________________________________________ ___________________

Billy Ray wrote:
> Well.... it would be best to know what the code is this time even though the
> symptons are similar.
>
> "twaldron" > wrote in message
> ...
>
>>I haven't had the error checked this time for a code, but the problem is
>>exactly like last time. I'm pretty sure the code was P0300 last time.
>>
>>tw
>>________________________________________________ _____________________
>>2003 TJ Rubicon * 2001 XJ Sport * 1971 Bill Stroppe Baja Bronco
>>
>>"There is a very fine line between 'hobby' and 'mental illness'."
>>
>>Pronunciation: 'jEp Function: noun Date: 1940
>>
>>Etymology: from g. p. (G= 'Government' P= '80 inch wheelbase')
>>A small general-purpose motor vehicle with 80" wheelbase, 1/4-ton
>>capacity and four-wheel drive used by the U.S. army in World War II.
>>________________________________________________ _____________________
>>
>>
>>Billy Ray wrote:
>>
>>>What code?
>>>
>>>"twaldron" > wrote in message
.com...
>>>
>>>
>>>>This is the second time this has happened, otherwise the Jeep runs
>>>>great. Once at about 15k miles and this time at about 50k miles, upon
>>>>cold starting, the engine stumbles (of course no gas pedal), runs really
>>>>rough for about 20-30 seconds, then planes out. This triggers the CHECK
>>>>ENGINE light. The vehicle runs fine after that, but the light stays on.
>>>>The first time, the dealer reset the light during a visit for a brake
>>>>rotor issue, but found no problems. Gas cap OK, both times. Suggestions?
>>>>
>>>>tw
>>>>--
>>>>______________________________________________ _______________________
>>>>2003 TJ Rubicon * 2001 XJ Sport * 1971 Bill Stroppe Baja Bronco
>>>>
>>>>"There is a very fine line between 'hobby' and 'mental illness'."
>>>>
>>>>Pronunciation: 'jEp Function: noun Date: 1940
>>>>
>>>>Etymology: from g. p. (G= 'Government' P= '80 inch wheelbase')
>>>>A small general-purpose motor vehicle with 80" wheelbase, 1/4-ton
>>>>capacity and four-wheel drive used by the U.S. army in World War II.
>>>>______________________________________________ _______________________
>>>
>>>
>>>
>
>

> Gas cap OK, both times. Suggestions?

May I venture a guess? I've seen this before and the cause is pretty
obscure, even to seasoned mechanics.

I am assuming you have the 4.0 with hydraulic lifters.

Sometimes, rarely, a stuck oil pressure relief valve piston will cause
the valves to hang upon when the engine is started cold, creating a
loss of compression, which triggers the MIL. Usually, the valve will
settle back into its normal position and all symptoms dissappear.
Sometimes for a long time, sometimes for a day.

Usually, you will get a bunch of codes aside from 300 pointing to
individual cylinders that are misfiring along with the 300, sometimes
not, depending on how the PCM was programmed.

If this is only happening when the engine is cold, this would be my
best guess. You could hook up a known-good oil pressure guage to
verify this. Other symtoms of this include oil filter expansion, oil
leakage, stalling on initial startup and hard restarting.

You will have to consult with your mechanic about a remedy; I can't
help you there.

-JD

I should also mention that high RPM valve float will sometimes cause
this as well, just in case someone here gets a P0-300 after drag racing
a Honda Civic.

-JD

The procedure is outlined here or if you stop by almost any auto-parts store
they will lend you a lend you a reader at no charge or they may read it for
you if they are not busy.

http://www.ptcruizer.com/computer-codes.html

If you send me an e-address I'll forward the appropriate FSM data to you.





"twaldron" > wrote in message
m...
> Yes, it would. I don't have a reader, so I'm looking to try a few common
> things prior to paying for a service visit.
>
> tw
> __________________________________________________ ___________________
> 2003 TJ Rubicon * 2001 XJ Sport * 1971 Bill Stroppe Baja Bronco
>
> "There is a very fine line between 'hobby' and 'mental illness'."
>
> Pronunciation: 'jEp Function: noun Date: 1940
>
> Etymology: from g. p. (G= 'Government' P= '80 inch wheelbase')
> A small general-purpose motor vehicle with 80" wheelbase, 1/4-ton
> capacity and four-wheel drive used by the U.S. army in World War II.
> __________________________________________________ ___________________
>
> Billy Ray wrote:
> > Well.... it would be best to know what the code is this time even though
the
> > symptons are similar.
> >
> > "twaldron" > wrote in message
> > ...
> >
> >>I haven't had the error checked this time for a code, but the problem is
> >>exactly like last time. I'm pretty sure the code was P0300 last time.
> >>
> >>tw
> >>________________________________________________ _____________________
> >>2003 TJ Rubicon * 2001 XJ Sport * 1971 Bill Stroppe Baja Bronco
> >>
> >>"There is a very fine line between 'hobby' and 'mental illness'."
> >>
> >>Pronunciation: 'jEp Function: noun Date: 1940
> >>
> >>Etymology: from g. p. (G= 'Government' P= '80 inch wheelbase')
> >>A small general-purpose motor vehicle with 80" wheelbase, 1/4-ton
> >>capacity and four-wheel drive used by the U.S. army in World War II.
> >>________________________________________________ _____________________
> >>
> >>
> >>Billy Ray wrote:
> >>
> >>>What code?
> >>>
> >>>"twaldron" > wrote in message
> .com...
> >>>
> >>>
> >>>>This is the second time this has happened, otherwise the Jeep runs
> >>>>great. Once at about 15k miles and this time at about 50k miles, upon
> >>>>cold starting, the engine stumbles (of course no gas pedal), runs
really
> >>>>rough for about 20-30 seconds, then planes out. This triggers the
CHECK
> >>>>ENGINE light. The vehicle runs fine after that, but the light stays
on.
> >>>>The first time, the dealer reset the light during a visit for a brake
> >>>>rotor issue, but found no problems. Gas cap OK, both times.
Suggestions?
> >>>>
> >>>>tw
> >>>>--
> >>>>______________________________________________ _______________________
> >>>>2003 TJ Rubicon * 2001 XJ Sport * 1971 Bill Stroppe Baja Bronco
> >>>>
> >>>>"There is a very fine line between 'hobby' and 'mental illness'."
> >>>>
> >>>>Pronunciation: 'jEp Function: noun Date: 1940
> >>>>
> >>>>Etymology: from g. p. (G= 'Government' P= '80 inch wheelbase')
> >>>>A small general-purpose motor vehicle with 80" wheelbase, 1/4-ton
> >>>>capacity and four-wheel drive used by the U.S. army in World War II.
> >>>>______________________________________________ _______________________
> >>>
> >>>
> >>>
> >
> >

fault codes are?????

twaldron wrote:

> This is the second time this has happened, otherwise the Jeep runs
> great. Once at about 15k miles and this time at about 50k miles, upon
> cold starting, the engine stumbles (of course no gas pedal), runs really
> rough for about 20-30 seconds, then planes out. This triggers the CHECK
> ENGINE light. The vehicle runs fine after that, but the light stays on.
> The first time, the dealer reset the light during a visit for a brake
> rotor issue, but found no problems. Gas cap OK, both times. Suggestions?
>
> tw
> --
> __________________________________________________ ___________________
> 2003 TJ Rubicon * 2001 XJ Sport * 1971 Bill Stroppe Baja Bronco
>
> "There is a very fine line between 'hobby' and 'mental illness'."
>
> Pronunciation: 'jEp Function: noun Date: 1940
>
> Etymology: from g. p. (G= 'Government' P= '80 inch wheelbase')
> A small general-purpose motor vehicle with 80" wheelbase, 1/4-ton
> capacity and four-wheel drive used by the U.S. army in World War II.
> __________________________________________________ ___________________

Or maybe the idle control circuit just wasn't able to respond as quickly as
it should to the unusual needs of a cold engine, hence the stumbling and
check engine light. When one of my vehicles acts a little "cold blooded" in
the morning, I just feed it some throttle. That usually fixes things. I
have triggered the engine light trying to crawl up a trail, at an engine
speed that was really too low, and almost stalling the engine. I don't know
if I would even bother trying to track this down, if it has only happened
twice in 50k miles.

Earle

"JD Adams" > wrote in message
ups.com...
> > Gas cap OK, both times. Suggestions?
>
> May I venture a guess? I've seen this before and the cause is pretty
> obscure, even to seasoned mechanics.
>
> I am assuming you have the 4.0 with hydraulic lifters.
>
> Sometimes, rarely, a stuck oil pressure relief valve piston will cause
> the valves to hang upon when the engine is started cold, creating a
> loss of compression, which triggers the MIL. Usually, the valve will
> settle back into its normal position and all symptoms dissappear.
> Sometimes for a long time, sometimes for a day.
>
> Usually, you will get a bunch of codes aside from 300 pointing to
> individual cylinders that are misfiring along with the 300, sometimes
> not, depending on how the PCM was programmed.
>
> If this is only happening when the engine is cold, this would be my
> best guess. You could hook up a known-good oil pressure guage to
> verify this. Other symtoms of this include oil filter expansion, oil
> leakage, stalling on initial startup and hard restarting.
>
> You will have to consult with your mechanic about a remedy; I can't
> help you there.
>
> -JD
>

You aren't one of those people who covers the 'check engine' light with
a piece of black tape, are you?

My Actron OBD scanner paid for itself the first time I used it. Just
used it to run a pre-emissions inspection check, and it caught a small
item that would have failed me. C'mon now...be a big boy...go buy one.
If it makes you feel any better, you can use it on any late-model
vehicle. Your neighbors might even want to slip you a 20 to borrow it
now and then.