P0300 random misfire. Have changed valve cover gasket set and intake manifold gasket set. Any more suggestions?

It does not throw codes" there isn't a word in engine diagnostics'. It displays or shows.. Good Luck


P0660 OBD II Trouble Code Intake Manifold Tuning Valve Control Circuit...

P0300 OBD II Trouble Code Random Multiple Cylinder Misfire Detected...

If the engine is misfiring the check engine light would be on and blinking and the engine control module (PCM) would store a fault code or codes for the cylinders that are misfiring. A lean code will not cause a misfire unless the engine has a vacuum leak most often at the intake manifold gaskets. A misfire code looks like this:

P0300-P0306 for 6 cylinder and P0300-P0308 for a V8.
P0300 indicated a random engine misfire, this can be caused by all kinds of issues.

I don't think you really understand what this fault code means, it means that likely all the engine cylinders are misfiring at random no set pattern, not any particular cylinder. I would start with checking for engine vacuum leaks like the intake manifold gasket. that is all I can say since you provided no make, model or year and engine type and size information.

code p0300 refers to random/multiple cylinder/s ---misfire detected=== causes spark plug/s--HT lead/s--injector/s---ignition coil/s--low compression --wiring
Seeing as you have covered all the electrics, now concentrate on the injectors and fuel pressures
If you will do all injectors and the fuel pressure is where it is supposed to be ( pressure test) then you will have covered all bases
Low compression will be in the one cylinder only ans will remain in that cylinder regardless of injector or plug changes
I would leave that to the last resort as if it is random, it may be a loose valve seat insert that moves randomly causing a compression problem

Hi there:

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.


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: 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.




Now, about P0660, check diagnostic test HERE.


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Misfire code I'd replace plugs wires buy a used icm

usually this code is followed by another number 1-4 or 1-6 or 1-8 depending on how many cylinders your vehicle has ,, what the code you got is a basic P0300 Random/Multiple Cylinder Misfire Detected 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
• 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 ope
  

Check for a vacuum leak all hoses and also check for leak in the intake manifold gaskets.This will cause a misfire and a code p0300

replace coil pack

P0302 is random misfire on cylinder #2.

Most comment cause is vacuum leak at the intake manifold and vacuum hose.

If you valve cover is leaking oil on then DO THE HOLD JOB.

Remove valve cover to gain access the intake manifold.

Change the intake gasket and valve cover gasket.