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Good Morning, i finally managed to seek advanced help in fixing my own car, my name is Stefan and i drive a chevy express out of necessity.
It got to me cheap but now its getting funny on me.
P0300 is a re occurring issue, many things tried,parts tried etc.
I can't seem to find the issue, history to the point where documetation is unclear or lost:
bought the car with broken serpentine belt.
replaced it and got told that it wasn't driven into overheating after the fact the belt broke.
Radiator had a leak too, replaced it as well with aftermarket product.
refilled coolant and got air out of system.
Car runs smooth in Idle...
Car has an Exhaust Manifold Leak and a low Voltage on the Bank 2 Sensor 2 O2 Sensor.
Misfire occurred first during reving up the engine in Park after replacing the radiator.
So far, have driven the car since registration daily and its a not hard code which mostly disappears after not being on the highway and run in city traffic on lower speed below 55 miles an hour and turning it on and off between errands.
I went for ignition System first and changed plugs and wires and it didn't changed anything even though the plugs had a 3/16 inch gap and where probably original, wires where all the same but one.
I read about further issues and ideas about the problem, had a p0171 and p0174 stored but relate that to the p0300 as and resulting issue.
An Engine Knock started occurring every now and then but went away but its definetely getting more often that it occurrs.
I checked Air intake Manifold Gasket for leaks with Water,
i sprayed the Sh... out of the Engine Compartment with Brake Cleaner and nothing.
I checked the Fuel Pressure and got 60 psi on a crank, i haven't gotten to the injectors yet.
I unplugged the MAF sensor and drove it, it ran fine and threw no codes on me.
I changed the MAF and still has the same problem.
But now it starts funny, only every second crank attempt when engine is cold.
I put a new Camshaft Sensor in by someone telling me that might solve the problem, but it didn't,
I put a new Crankshaft sensor in as well and it didn't solve the problem, but i haven't relearned it yet.
I found that i am loosing little coolant over time but haven't found a leak or wet spot under the car, i also loose Engine Oil over time
but have no Oil on the road where i usually park the car.
Recently Check Gauges Sign came on and off, and Oil pressure warning light/service light.
Oil Pressure was low, refilled Engine Oil to specs and it seems fine.
I have found a little bit black sod in Radiator Cap.and some moldy looking spots in the coolant reservoir.
I have no white or black smoke coming out of the Tailpipe and the engine doesnt overheat while driving it in any condition...
I am about to leave it and drive it until it simply dies on me...
Hey Stefan! I moved your topic to the Repair section. More traffic, more users, more responses.
What kind of scan tool do you have access to? I ask because P0300's on GM's say 'random', but they rarely are. The OEM Misfire data list will almost always reveal which cylinder(s) are the real offenders. This can go a LONG way in narrowing down the list of suspects.
Are the P0300, P0171 or P0174 still stored? If so, can you access the freeze frame data?
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