I have a 2006 jeep commander 3.7 with random misfire what is the cause? p0300

SOURCE: Random engine misfiring- fault code P0300- 1999 cutlass

Could be coil pack(s), fuel injectors, etc. Rather than retype it, just check out this great article on P0300 random misfire - http://www.obd-codes.com/p0300

SOURCE: I am getting a misfire

I've got a 2002 Grand Prix GTP 3.8L Supercharged V6, nearly the same motor.
I had the exact same problem, misfire on Cyl. 5 and random/multiple misfire.

I replaced all the wires, plugs, coils, and even the ignition module. My next thought was either fuel or exaust.

Replaced my Cat. with a 2.5" ZZP downpipe, and the car ran alot better, but still had a tiny bit of hesitation over 4000rpms.

So i checked all the fuel injectors, and the #5 injector was bad.

To check, get an ohm meter, remove the injector connectors, and contact the 2 posts inside the injector. They should read between 12.4-14 or so.

Mine was at 11.2.

Replaced all the fuel injectors, and she runs like a champ

SOURCE: misfire of the #3 cylinder, 4.3 6 cyl

R THEY WIRED CORRECTLY,WITH THE SAME GAP??

SOURCE: 02 sensor p0136 and cylinder misfire p0300

Most likely you do not have bad O2 sensor or coil sience you have P0300 code.
Check for vacuum leaks first , this is very common problem(vacuum leak) , lean mixture will cause misfire. I'm tallking about V6 engine , 4cyl have same problems but for misfire it may have bad coil (they under recall now).
Also check condition of air mass sensor , if it's dirty ,
buy air flow sensor cleaner and clean it according to user manual on the can.(air mass sensor can cause
O2 sensor code)
Check vacuum hose to fuel pressure regulator.
There are many more things to check , but that for mechanic shops after you try this.

ZJ Limited

• 17989 Answers
• Posted on Jul 13, 2011

SOURCE: 2005 Hyundai Tucson 2.0L During start-up

A P0300 diagnostic code indicates a random or multiple misfire. If the last digit is a number other than zero, it corresponds to the cylinder number that is misfiring. A P0302 code, for example, would tell you cylinder number two is misfiring. Unfortunately, a P0300 doesn't tell you specifically which cylinder(s) is/are mis-firing, nor why.

For example, a P0302 code means that the the car's computer has detected that one of the engine's cylinders is not firing properly. In this case it's cylinder #2; same condition in P0301 - cyl #1, P0303 - cyl #3 and P0304 - cyl #4.

A code P0300 (or 301, 302, 303 or 304) 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

About your possible solutions, if 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.



So, your code P0170 is one that surfaces with certain makes of automobiles more than others. In writing this article I've added Mercedes-Benz-specific info since it seems that M-B (and VW) are most prone to having this P0170 surface along with misfire codes or other fuel trim codes. P0170 means there was a malfunction in the computer's control of the air:fuel ratio.

It also indicates that the fuel trims reached their limit of adding fuel while trying to compensate for a actual or perceived rich condition. When the fuel trims reach their rich correction limit, the PCM (Powertrain Control Module) sets a P0170, indicating a problem or malfunction in the fuel trims. It may also have a P0173 referring to the same malfunction but on bank two.

Potential causes include a vacuum leak, unmetered air leaks Fuel saturated engine oil Leak in turbo air charge hoses (if equipped) Possibly bad O2 sensor (If Mercedes, may require adaptation with M-Benz compatible scan tool.) Oil contamination in MAF connector or O2 sensor connectors. Also check ignition coils, cam and crank sensors, and oil sensor for leakage contributing to oil intrusion in wiring harness. Defective MAF (Mass Air Flow) sensor (especially on Mercedez-Benz and other European autos. There are a lot of problems with aftermarket MAF sensors).

If you have this code and access to a scan tool, observe the MAF sensor reading in grams/sec. The reading will be different for different automobiles, so get a good spec. I'm going to stick with what would be normal for a Mercedes (1.8L), since they have the bulk of the trouble. Expect to see at idle 3.5-5 g/s (ideally). At 2500 RPMs with no load it should be between 9 and 12 g/s. On road test, at WOT (wide open throttle) it should be 90 g/s or well above. If it's not in specs, replace it. Be careful of Ebay MAFs. Often they don't work according to OE specifications. If the MAF checks out and there is no oil intrusion at the connector, check fuel pressure and ensure that there are no leaks at the regulator internally or externally. Check all vacuum hoses and confirm none are cracked, disconnected or missing. Make sure there are no vacuum leaks at the intake manifold gaskets or tears in the air supply hose. If the engine is turbo charged, be sure the hoses are in good condition and have no leaks. Leaking turbo pressure hoses could cause a rich condition. Inspect the condition of crankcase vent hose under intake manifold and operation of check valve in the hose. (In the "What are the causes?" section) If there doesn't appear to be any problems with the fuel pressure, MAF or vacuum hoses, then inspect the O2 sensor connectors for oil intrusion. A bad O2 sensor could cause a P0170, or P0173. Repair cause of oil leak and replace oil-fouled O2 sensor.

This is location diagram...



Bank 1 is always the side of the engine with cylinder #1.
Bank 2 is always the side of the engine with cylinder #2.

Bank 1 is the bank of cylinders on the firewall side.
Bank 2 is the bank of cylinders on the radiator side.

Sensor 1 is the O2 sensor before the cat.
Sensor 2 is the O2 sensor after the cat.

So the one you want is the sensor AFTER the cat on the FIREWALL side of the engine.

Hope this helps.