'misfire' codes..WTF

in4aride

NAXJA Forum User

Location

Montrose

• Jan 13, 2010

• #1

'01 XJ. Has about 100k. Purchased in AZ and brought to CO.
Upon start up, it runs like absolute crap, and throws codes for misfires in cylinders 3 and 5.

As it's not my jeep I can't really get time to look at it. But curious what you guys might think would be a good starting point?
Coilpack? Spark plug? Injector?

 

Last edited: Jan 13, 2010

in4aride

NAXJA Forum User

Location

Montrose

• Jan 13, 2010

• #2

Sorry. A bit more info.....

It doesn't always start and run like crap. Sometimes it runs just fine.

After driving it a shirtways the 'roughness' goes away and it drives fine. Even with the check engine light still on.

When running rough. The jeep requires a lot of throttle before idle will pick up.

 

lazyxj

NAXJA Member #1310

Location

Los Angeles

• Jan 13, 2010

• #3

in4aride said:

'01 XJ.
Upon start up, it runs like absolute crap, and throws codes for misfires in cylinders 3 and 5.

Click to expand...

[FONT=&quot]Does it do it when starting cold or on hot re-starts?

Hot re-start misfire problems are common in the 2000-2001 XJs due to the location of the two mini-cats, located in the exhaust manifold.
A search will find a lot of information on this.

Cold start problems could be a lot of things; bad plugs, plugged injectors, failing coil packs, etc.[/FONT]

 

Tim_MN

Freakish Hand Strength

NAXJA Member

Location

Minneapolis, MN

• Jan 13, 2010

• #4

in4aride said:

... it drives fine. Even with the check engine light still on.

Click to expand...

Download the CEL codes and start there.

Get some tuneup parts, Throttle Body and Idle Air Controller cleaner spray, and some injector cleaner while you are having the codes downloaded at the auto parts store.

 

joe_peters

NAXJA Forum User

Location

Grants Pass, OryGun

• Jan 13, 2010

• #5

It may be the heat-soak problem, even when cold. Doesn't sound logical, but the result of the heat-soak issue is pooled fuel in the intake causing rough running on hot restart, but that fuel pools in the intake when shut down for the day too.

As said, search heat-soak.

Quick and dirty test for heat-soak: after driving the vehicle until it is good and hot, shut it down and open the hood. Leave the hood open for about 30 minutes to an hour. If after doing this, on restart if the symptoms are gone or less severe, you have heat-soak.

 

I

Ian Christiansen

NAXJA Forum User

Location

Shelby Township, MI

• Jan 13, 2010

• #6

Sounds like the heat-soak problem.

 

in4aride

NAXJA Forum User

Location

Montrose

• Jan 13, 2010

• #7

Been reasearching the hear-soak issues and seems like a good probability to be the issue my friend is having. I'll be sure to try and do the simple 'tests' for heat soak and see what happens.
Thanks for the info guys

 

MJR

NAXJA Forum User

Location

Costa Mesa, CA

• Jan 13, 2010

• #8

There may be a controller flash and there was a recall for intake manifold debris shield along with a tsb about hot soak and insulating the #3 injector. Only the CA emissions package (used by 4 other states) had the pre-cats, the federal ones just had a Y pipe.

 

B

birchlakeXJ

NAXJA Forum User

Location

Melrose, MN

• Jan 13, 2010

• #9

For misfires, I always start with fresh plugs. Don't want to be chasing your tail for a worn plug.

TSB is for heat soak misfires and rought starts; cylinder #3 which is most susceptible. The mfg. fix though of insulating the injector is getting mixed results. Works for some, helps a little for others, of no value to some as well.

Running fuel injector cleaner (Lucas/Techron, etc) never a bad idea

Coil pack is also a possibility as well as fuel injectors.

 

GrimmJeeper

NAXJA Forum User

Location

Gardena, CA

• Jan 14, 2010

• #10

my mother's 4.7 v8 WJ is doing the same thing.... could it be related to this problem at all? I realize it's a different engine, but I'm stumped. coil packs replaced and injectors machine cleaned already.

 

Last edited: Jan 14, 2010

MJR

NAXJA Forum User

Location

Costa Mesa, CA

• Jan 14, 2010

• #11

GrimmJeeper said:

my mother's 4.7 v8 WJ is doing the same thing.... could it be related to this problem at all? I realize it's a different engine, but I'm stumped. coil packs replaced and injectors machine cleaned already.

Click to expand...

Is the WJ really misfiring or just setting codes? It could be the PCM (setting codes but runs fine), plugs, coils, wiring, or valves/seats (seen a few drop valve seats but you'd have more issues).