Anyone know anything about Jeeps? - PeachParts Mercedes-Benz Forum

SirNik84 · #1 08-20-2008, 12:11 PM

My mom has a 2001 TJ Jeep with the 4L engine.

Its been having an uneven idle and it misfires every once in a while. my mom said it was due for an oil change and new plugs. so i changed them last night. this morning it still has an uneven idle, and still has a misfire.

I'm no expert when it comes to computer controlled crap. but if this was a real car, the kind that has a distributer cap and wires i would change the cap and rotor and change the wires. but this thing has a coil pack that sits directly on top of the plugs. where can the problem be?

anyone have any experience with these jeeps? or coil packs.

Angel · #2 08-20-2008, 12:30 PM

I'm not even into jeeps but I knwo that they have more forums devoted to them than MB's......

That said, its a 2001, its OBDII so take it to Autozone and have them read the codes (I assume the Check engine light is on) Autozone will make some recommendations and try to sell you stuff, but I'd jsut post the codes (they will be something like "P0056" or "T0131" up here, we can help with that. No sense replacing stuff willy-nilly until we at least know what the computer thinks (I agree that that computer is not always right though...)

I agree that changing coils/wires ad plugs would probably help, but coilpacks or coil-on-plugs are expensive- too expensive to guess IIRC.

-John

SirNik84 · #3 08-20-2008, 12:36 PM

the check engine light was on. for about a day, then while driving down the freeway it went off. its been off now for the last 5 days.

SwampYankee · #4 08-20-2008, 01:06 PM

Quote:

Originally Posted by SirNik84

the check engine light was on. for about a day, then while driving down the freeway it went off. its been off now for the last 5 days.

Did you change wires too or just the plugs?

Might be a bad injector? Bad plug from the manufacturer? If you have time try swapping them out and seeing if the problem follows it to the other cylinder. Check the gaps, too. And avoid the fancy high tech plugs, plain old Champions or NGK will do the trick.

Pull the codes and see what comes up then go from there. It could be the pack going south.

The check engine light might have been from a loose gas cap and may have reset itself.

I like www.jeepforum.com but there are tons of other good sites out there. Like most sites be sure to use the search function first before posting a question. Some people seem to have nothing better to do than jump down newbie's throats for such an offense.

Does the mifire eventually smooth out? There was a TSB about a recurring #3 cylinder misfire due to inadequate heat shielding leading to a persistent misfiring problem. Here's that notice (see the 2nd part):

0900303 - 4.0L MULTIPLE CYLINDER MISFIRE
Date: 08/01/03
Model Year(s): 1999-2004

Description: NOTE: THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH A 4.0L ENGINE. This bulletin involves inspection of all engine exhaust valves and a decarbonizing procedure if necessary.

Details: The customer may experience an incident of engine misfire during certain vehicle operating conditions. The misfire may occur when the vehicle is operated between 50 - 70 MPH and under light loading conditions, e.g. slight uphill road grades. This condition may occur at all ambient conditions, but is more noticeable when ambient conditions are less than 0 C (32 F).

If the vehicle is equipped with On-Board Diagnostic (OBD), a MIL illumination may also have occurred due to Diagnostic Trouble Code (DTC) P0300 - Multiple Cylinder Misfire. Various single cylinder misfire DTC?s may also be present. If the frequency of misfire is high the Powertrain Control Module (PCM) may place the engine in ?Limp-In? mode.

The misfire condition may be caused by one or more engine exhaust valves that are slow to close. Late closure of an exhaust valve may be the result of no valve rotation and associated build up of carbon on the exhaust valve stem.

This condition may occur when the engine is not allowed to run at engine RPM?s that are greater than 3,200 RPM. At 3,200 RPM or higher the engine exhaust valves will rotate if not impeded by high carbon deposits. Low engine RPM?s and high carbon deposits are associated with short trip driving where the vehicle engine is not allowed to fully warm to normal engine operating temperatures. Cold ambient temperatures will increase engine warm-up time and add to the opportunity of carbon deposit build-up on the stem of the engine exhaust valve.

And

1803103 - 4.0L ROUGH ENGINE IDLE AFTER RESTART FOLLOWING A HOT SOAK
Date: 09/05/03 (supercedes 1802702 dated 09/06/02)
Model Year(s): 1999-2004

Description: NOTE: This bulletin applies to vehicles equipped with a 4.0L engine. This bulletin involves the installation of a fuel injector insulator sleeve.

Details: Customers may describe a 20 to 30 second rough idle following the restart of a heat soaked engine. This condition may be most noticeable when the engine is restarted following a prior 10 to 20 minute heat soak in hot ambient conditions of approximately 32 C (90ºF) or higher. This condition may be consistent with short city stop-and-go driving trips and can be aggravated by the use of fuel with a high ethanol content. Depending upon various conditions a MIL may occur due to DTC P0303 - Cylinder #3 Misfire.

This condition may be caused by heat from the exhaust manifold that following engine shut down migrates to the area around injector #3 and causes fuel vapor to form within the injector. This in turn may cause a momentary misfire of cylinder #3 until the fuel vapor is cleared of injector #3. The insulator sleeve lowers the injector #3 temperature to a point below which the fuel will not normally vaporize.

If vehicle exhibits a rough idle, and if a misfire of cylinder #3 is observed following a 10 to 20 minute hot soak, perform the Repair Procedure.

Parts required:
56028371AA Ignition Wire Shield

Repair procedure:
1. Cut insulator sleeve, p/n 56028371AA, to make two (2) insulator sleeves about 25-30 mm (1 in.) in length. See diagram.
2. Install one sleeve around injector #3, with the slit on the upward facing side of the injector. Install the other sleeve with the slit on the downward facing side of the injector.
3. Confirm sleeve is flush to intake manifold surface around injector.
4. Check injector #3 wire and ensure that the injector is rotated to a 2 o'clock position (from driver?s side of vehicle).

SirNik84 · #5 08-20-2008, 01:19 PM

Thanks Swamp,

No plug wire to change. there are the little sleeves that extent off the coil pack, but i did not change those.

I think the MULTIPLE CYLINDER MISFIRE sounds like my problem. when i get on it. and rev the engine up while driving there is no misfires. and it will drive normal for the rest of that trip. but if I'm in traffic, like this morning then its really bad.

I talked to my mom and she is going to make a post on jeepforum. shes a member... my mom is pretty internet savvy. so we'll see where that goes.

catmandoo62 · #6 08-20-2008, 09:30 PM

i thought you wanted info on jeeps!as far as i'm concerned jeeps went out of production when chrysler took over in 1976 or 77.

OMEGAMAN · #7 08-20-2008, 10:44 PM

what plugs did you instal in there?

Emmerich · #8 08-20-2008, 11:00 PM

most check engine lights are caused by emission system problems. A bad O2 sensor can cause a LOT of what seems to be unrelated problems

cdplayer · #9 08-20-2008, 11:46 PM

I sold my Overland because it was plagued with a problematic dual climate control. It was the WJ class. A wealth of information at www.wjjeeps.com

I realize yours is a TJ but systems are similar.

SirNik84 · #10 08-21-2008, 11:46 AM

NGK plugs.

ImBroke · #11 08-21-2008, 04:31 PM

Idle sounds IAC related. That will throw a code. Misfire could be a few things. Gotta get the codes, or you'll be throwing parts at it. Even if the CEL is not lit now, the codes will be stored in the computer as a history.