Today, I was out running errands and when I started the Jeep to come home, it was running rough. I put it in Neutral and gassed it for a few seconds and it settled down just fine. (This has happened a few times over the last few months.) While driving home, the check engine light came on. When I got home, I did the on-off-on-off-on thing with the key and it cave me a P0300 code. I looked it up and it said: Multiple Cylinder Mis-fire.

Anybody got any ideas as to what may have caused this? Or how to fix it? I'm going to go and check my vacuum hoses to make sure nothing came undone under the hood.

Thanks in advance for the help.

that code is just what it says. random misfire. the computer is not pinning it down to a certain cylinder, it could be anything. state of tune, injector, vacuum leak, fuel pressure, anything that can cause a misfire.

tuned up lately?

gotta love google
i found em, u read em lol


Posted at Sun Sep 28, 2008 11:53 am
By rasmataz, Certified 2CarPros Master Technician


A code P0300 may mean that one or more of the following has happened:

Faulty spark plugs or wires
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector(s)
Burned exhaust valve
Faulty catalytic converter(s)
Stuck/blocked EGR valve / passages
Faulty camshaft position sensor
Defective computer
Possible SolutionsIf there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs
, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.


http://www.2carpros.com/forum/1997-j...-vt191583.html
Getting an MIL Error Code P0300 - JK-Forum.com - The Ultimate Jeep JK Wrangler Bulletin Board
P0300 Error Code, Opinions Greatly Appreciated - JeepForum.com
- Just bought a Grand Cherokee with P0300 P0301 P0302...egads! - OBD-Codes.com

Possible water in your fuel that can cause the PO300 code,When was your last Tune Up (Dont' Use Bosch!) Check the coil tower for corrosion & the dist cap where the coil wire plugs in, Try a bottle of fuel dry 1st

if your still having problems, things i would check or do: clean throttle body/intake, check plugs, i kept throwing all sorts of codes and it ended up being an o2 sensor so i replaced them all, one code since and i had burned out the front minin cat due to the fuel mixture the cpu was putting in due to a faulty 02 sensor. i had all sorts of misfires, sometimes it would tell me the #1 cylinder.

Thanks for the responses....

P0300 is the only code it is throwing....

No cap and rotor, because there is no distributer! Coil rail controlled by the friggin computer. Only 45k miles on the motor, so it shouldn't be plugs. Also, hasn't rained here in weeks, so fuel should be dry. Checked vac hoses, all ok...

Thanks for the google links... I looked, but didn't find anything specific.

Are ODBII codes universal? or specific to the model/year?

Still under warranty, maybe I'll take it to the dealership tomorrow and see what they say...

ah, your under warranty!?

let those guys at the stealership troubleshoot it for ya for free!

if they say its not covered at least you know whats wrong with it.... or at least what they THINK is wrong with it lol.

im having the same problem. I took it in the shop and my cat. converter was bad.

You haven't changed out the factory plugs in 45K miles? The factory uses conventional non-platinum plugs in your engine and I'd be very surprised if they'e not past toast with that many miles on them.

If it were me, after reading everything you've done, I'd go right out and buy a set of Autolite APP985 (a dual-tipped platinum) plugs and install them. Do NOT install the AP985 plugs which don't work well in your distributorless engine.

Finally fixed my P0300 engine light! I had this P0300 and P0304-5-6 problem for months. Purchased a 2002 Jeep Wrangler Sport 4.0L Auto that had this problem . Read a lot on the forums and went down the same path that it looks like most of us have done.

Replaced Plugs
Did a compression check (good)
Replaced Coil Rail
Replaced Camshaft position Sensor cap
Replace Fuel Pump (it was dropping back pressure so needed it anyway)
Took it to the dealership and they had it several days. They said they need to pull the head because they see coolant leaking on plug 3 and wanted $900 to get started. Possible cracked head or warped or leaking gasket (told them thanks but no thanks)
Removed head myself and had it machined with valve spring test – Machine shop said Chryslers are famous for burring exhaust valves , especially if fuel pressure is low. (Leans out)
Head was fine (other than burnt valve seats)
Replace Timing chain (since I was in there already)
Still received error epically when engine hot driving around 40 to 45 miles an hour.
Sent ECM (Computer) off to Florida to be rebuilt
Still received error
Then I replaced the Crank Position Sensor.

Fixed it!!!!!!!!!!!!!!!!

I think what was going on, is the 2002 crank trigger sensor has a piece of what looks like construction paper on it. The instructions say it is used to set the proper gap and to push the sensor all the way in and tighten down the locking bolt. The paper will then be sheered away. I noticed that the one I removed still had the paper on it. So I bet it might have been a good unit just not inserted fully. The jeep expert at the auto part store says he pushes it in until it hits then backs it off a little. I did not do this.. My guess the previous mechanic did this also thus leaving an exessive gap between the sensor and the flywheel. Hope this helps some one else. Wish I started with this first.

My 2013 JKU just started studdering and stuff this morning and threw the P0300 and P000D code I cleared it with an OBDII and its alright right now. If it does it again it'll be in the stealership.

Having the same problem on my 2000 TJ 4.0L Ive pretty much done everything WINGRANT also did with codes P0300 P0306 P0304. Im going to replace the Crank Shaft Position Sensor today see if it will solve the Multiple Misfire! Wish me luck!! (Crossing Fingers)

Well this sucks, i put in a new crank shaft position sensor and still MIL light comes one. Ive noticed when I rev the engine in park to about 2500 to 3000 MIL light comes on and flashing. Bad PCM maybe??? Camshaft position sensor?

Have you swapped the plugs/leads or troubleshooted anything else?

Hi All, I am new to this site. I am also having this issue of a code of P0300 but I'm also getting multiple codes with it P0152, P0031, P0037, P0051, and P0057.I have replaced all the O2 sensors the codes cleared for about 10-15 miles and came back. I'm going to change the plugs today and see if that helps but I was wondering if anyone else has had this problem and what their solution was. Any and all help would be appreciated.
Thank's Billy