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I have a random cylinder engine misfire, it makes my truck studder while driving. I have replaced the cap, rotor, plugs, wire, coil, ignition module, EGR valve, injectors, fuel filter and did a compression check on cylinders after replacing head gaskets and fuel compression check all tested good. I figure the only 2 things left to do is the computer and the fuel pump. Any suggestions as to what else it could be?
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If it was just cylinder 2 or 3, the code would be 0302 or 0303. Instead, you have random misfires (probably) such that you should be checking things that affect the whole engine. Vacuum leaks, bad plug wires, bad coil(s) or ignition module are most likely, but even clogged exhaust, O2 sensors and bad battery can cause these problems. Yes, a battery can be good enough to start your car but still be bad enough to affect performance. If I had to guess, I would start by testing the ignition module. Most parts stores can test this if you remove it and carry it to them.
HARD TO SAY WITH OUT BEING THERE BUT THIS MIGHT HELP .
Crankshaft sensor Was the trouble with my 99 Chevy truck after replacing many components like coil cap rotor wires and so on . http://www.obd-codes.com/p0102
Code P0300 Causes and Fixes
Code p0300 is a code that is generated when your engine has a misfire that is not related to only one cylinder. Sometimes this code will be set in addition to other codes such as p0301 which means that there is a misfire on cylinder 1 (cylinder 1 is the number one cylinder when looking at the firing order. It is generally the forward most cylinder on the engine.). If these engine codes are present as well the you should diagnose those first as they are probably causing code p0300.
This code will set your check engine light and needs to be fixed as soon as possible. If it is not then you will probably need to replace your catalytic converter as well as the problem that is causing your misfire.
There are many causes for this obd code. Since it is a "random misfire" or "multiple misfire" this means that the misfire is on different cylinders and not just one all the time.
Common Causes
Low Fuel Pressure
Vacuum Leak
EGR system malfunction
Internal Engine Problems (such as low compression)
I WOULD REPLACE DISTRIBUTOR CAP AND ROTOR.MARK LOCATION OF ROTOR OR MAKE NOTE SO YOU CAN INSTALL NEW ROTOR IN CORRECT FIRING POSITION. IF THIS CAR HAS A LOT OF MILES I WOULD REPLACE DISTRIBUTOR CAP, ROTOR.SPARK PLUGS AND WIRES.REPLACE IGNITION COIL.CLEAN FUEL INJECTORS, FILL GAS TANK UP TO 3/4 TO FULL TANK OF GAS POUR CAN SEAFOAM IN FUEL TANK IT WILL FLUSH OUT THE FUEL INJECTORS WHILE ENGINE RUNNING OR DRIVING CAR. REPLACE FUEL FILTER. REASON I SAY DO A TUNE UP PROBLEM COULD BE MINOR FIX.COULD NEED TUNE UP.IF TUNE UP DONT HELP THEN YOUR PROBLEM IS DISTRIBUTOR OR THE CAMSHAFT SENSOR INSIDE OF DISTRIBUTOR.THAT WOULD SET OFF CHECK ENGINE LIGHT.BUT I WOULD SAY TUNE UP COULD FIX PROBLEM.
did the code set for multiple/random misfire or did it set for a particular cylinder or cylinders?if it is random or multiple misfire you may want to check the fuel pressure and volume and for a vacuum leak. if it is a particular cylinder or cylinders then check your coils and also the compression to make sure the engine rebuild is good and something didn't go wrong.
Replace your O2 Sensor and Spark Plug Wires. If you still have the Random Misfire, replace your Spark Plugs, then Replace your Distributor Cap and Rotor. If you still have the Random Misfire you may have a Timing Problem, or Ignition Coil problem.
Do an injector balance test and a cylinder leakage test. Lets make sure its not fuel related. Most important lets make sure you don't have a vacuum leak.
Basically this means that the the car's computer has detected that not all of the engine's cylinders are firing properly. A P0300 OBD DTC 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. 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. 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.
If you have someone scan it with a scan tool that gives you data stream they can tell you exactly what cylinder is doing it. You might have a bad coil or wire.
Misfire on cylinder 5 code comes on
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