Question about 2003 Hummer H2

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P0300 - (random misfire) only happens when the engine is cold (hasn't been run). I erase the code and restart the engine and the misfire does not happen again. It can be fine all the while the engine is hot and running. But happens again when the engine is cold again.

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First start by making sure that the spark plugs are AC Delco plugs or other WILL trigger a P0300. If these are good, the next thing to check is the coolant temperature sensor(ECT). If this is problematic, it will cause too much fuel to be delivered and misfires to occur on all cylinders.

Posted on May 09, 2010

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Posted on Jan 02, 2017

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GMC Sierra with the code P0300 Q: I have the 2003 GMC Sierra with the code P0300. What could be the problem? A: The code P0300 means "Random Cylinder Misfire". This means that the engine computer has detected that one or more of the cylinders misfire randomly. This code could take some time to diagnose, as there could be a wide range of reasons for the engine cylinders to misfire. Here are just a few examples: bad spark plugs, ignition wires, distributor cap/rotor, bad fuel injectors, bad airflow sensor, broken or weak valve spring, leaking valve, low fuel pressure, manifold gasket leak, clogged catalytic converter, etc. Take your truck to a knowledgeable mechanic and have it check out - driving with the misfiring engine can damage your catalytic converter.
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How do i fix my Mercury Villager 2002 with random misfire?


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Random misfire with code PO300 07 Nissan titan. Put new spark plugs in and a fuel pump still hase vary bad miss


P0300 is random misfire code P0301 would be cyl # 1 etc.
With the odb2 scanner at erase codes turn the engine off. With the key in the run position erase the codes. Run the diagnostics again. If you still have P0300 code Check the plug wires. Loss of compression will cause misfire but it would not be random.

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1997 Oldsmobile Cutlass P0405 EGR Error Code


P0300 Diagnostic Code - Random Misfire
Technical description:--
Random/Multiple Cylinder Misfire Detected:---
Exactly what does this code means:--
Basically this means that the the car's computer has detected that not all of the engine's cylinders are firing properly.
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.
Symptoms:--
the engine may be harder to start.the engine may stumble / stumble, and/or hesitate.
other symptoms may also be present…There may be rough idle, sputters and stalls and jerks.
Causes:--
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 solutions for this error problem:--
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 vehicle, 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 un-metered air getting past the airflow sensor, or an EGR valve that is stuck open.
Thanks. Keep updated for any more query. You can rate this solution and show your appreciation.

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