random miss fire

Asked by Sep 12, 2016 at 07:21 AM about the 1999 Chevrolet S-10 2 Dr LS 4WD Extended Cab SB

Question type: Maintenance & Repair

I have a 99 s10 4.3 i have replaced cap rotor wires
coil maf map egr gasket throttle position sensor
the problem will go away for a bit when i replaced
something but would eventually come back what
am i missing ???

4 Answers

77,905

P0300 CHEVROLET - Cylinder Misfire Detected Random Cylinders --- Possible causes - Faulty spark plug (s) - Faulty ignition coil (s) - Clogged or faulty fuel injector (s) - Intake air leak - Fuel injectors harness is open or shorted - Fuel Injectors circuit poor electrical connection - Ignition coils harness is open or shorted - Ignition coils circuit poor electrical connection - Insufficient cylinders compression - Incorrect fuel pressure --- The P0300 code means that a cylinder(s) is misfiring or is randomly misfiring. Start by checking for intake leaks, intake gaskets are common caused of multi-cylinder misfiring. If no leak are found the next step is to replace the spark plugs. If the problem persist more tests needs to be done to diagnose problem. Also there is a service builtin on this....2000-2008 Chevrolet Factory Service Bulletin OBDII Code P0300

70

Do tests, don't buy parts! Test EGR for back pressure because the number 1 reason for random misfire is a plugged cat or exhaust.

So i did some more testing and i had just replaced my map sensor and now if i unplug the sensor theres no miss but as soon as i plug it back in it starts missing the scaner says 10 for my manifold pressure doni have a manifold gasket leak?

77,905

If you have checked the vacuum pressure at an idle and you are only getting 10 inches vacuum, then there is a problem. Manifold vacuum should be around 17 to 20 in. at an idle. Ether a vacuum leak, or low compression in the cylinders.

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