P0300 Pontiac Code - Engine Misfire Detected

I replaced the spark plugs and wires still getting the misfire code next I am going to put heat and fill up with premium gas and see if that helps

That's a good start. If possible add a fuel additive to help clean the fuel injectors.

i also replaced spark plugs and i added fuel addictive. so must me a leak correct?

What year and model is your Pontiac?

Hi.am getting the code. P0171 saying. Fuel trim system lean bank 1

What model and year is your Pontiac?

More Information: https://www.autocodes.com/p01...

Hi, after few weeks wjth po300 code I change the following,spark plugs,wires coil pack,egr valve. Pcv valve,then change to po305 also change injectot #5. Run more than 100 miles and today start again po300. Pontiac Grsnd Am 2004. What can I do?

Unfortunately there are many things that can cause that problem. Next step is to perform a compression test. Also, check for intake leaks and if possible add a fuel additive.

2005 Pontiac Wave, po300 code, have changed 2 oxy sensors, coil pak, camshaft pos sensor, plugs...still misfires, will go up to 5000rpm great on slow accelaration, but misses BADLY when you step on it quickly and misses all the way up to 5000 rpm....in other words, driveable but you can't get out of the way if you have to, it just chokes! HELP!!

Since you already replace many parts, the next step it's performing a compression test, to check if the engine have a blown head gasket.

with a blown head gasket, would there not be blow back in the rad, or other overheating problems? Problems use to be so much easier to detect before all these 'sensors' and computer links came along!

No necessarily, you can have a blown head gasket with the symptoms you describe. Also check for intake leaks.

I have a 97 Pontiac sunfire se 2.2 L and I had the codes p0300, p0420, and p0440. I bought a new valve gasket cuz there was leakage coming out from passenger side by power steering. While doing that I decided to clean the carburetor and valves under as well. Let it dry up but I did end up using about half or maybe more of a can without realizing it.. Then put everything back together and now it won't start.. Took plugs out and letting them sit overnight.. What else could be the problem???

A 97 doesn't have a carb

2005 pontiac aztek 3.4 check engine light misfiring is what the code read I've changed all 3 coil packs checked the air filter added Lucas brand new plugs and wires has trouble starting have to floor the gas peddle in order for it to start then it idles low and dies when I get it into drive it runs great but in reverse and idle it dies I need help also whitish brown smoke coming from exhaust

What Lucas did you use? for fuel injector cleaning? There is a factory service bulletin (See "Tech notes" above that suggest that the fuel injector could cause a cylinder misfire code. You may have have to use more than one bottle of fuel injector cleaner to clean the injectors an you should uses high octane gas for a couple of weeks to see the results.

Hello -

My pontiac g5 is getting this p0300 code only after driving on the highway (which is most of my driving). When I am off the highway for 10 miles or so it turns off. I have no other symptoms than the check engine light. I have ran seafoam and lucas injector cleaner through the fuel system, but do not want to start changing all sorts of parts without knowing what is causing the issue.

Have you replace the spark plugs and air filters lately? you could start with that, which is part of the regular maintenance and use high octane gas for a few weeks.

I have an 01 Grand Am. I had trouble with it overheating and I parked the car and tried fixing it. I replaced the water pump, the thermostat, the thermostat sensor, the heater core, and the radiator. So I decided to replace the head gaskets. They were clogged and in bad shape. I took the heads to a machine shop to get a valve job and be resurfaced. I bought a gasket kit for the motor and replaced all gaskets. Bought new plugs and wires and it's misfiring! The P0300 code is showing up and it runs like doo-doo. What could possible be wrong? How should I go about trying to fix it? Or should I cut my losses and replace the motor?

Could these symptoms happen if sugar was put in gas tank?

Yes, definitely.

I have a 2002 Pontiac grand Prix gt sparks plugs was changed new battery an a oil change an a new Cadillac converter was put on but my car keeps misfiring an shuting off

I have a G5 Pontiac 2007 2.2 with a random miss fire code I had a mechanic do a compression test and a the pressure was good , leak test that was good , I changed to spark plugs and coils .
I even changed the engine module and I'm still getting the 300 random miss fire. Don't know what to do...

i have a 2000 grand prix gtp that is randomly misfiring. I have good compression (150+ psi each cylinder) fuel pressure is around 50 psi, spark plugs and wires are new AcDelco Professional double platinum plugs and professional wires. replaced one coil pack because I saw a crack in it and none of that helped. I dont have any intake leaks. not sure what the problem is, does any one know?

Besides what you have done, I would recommend replacing the Positive Crankcase Ventilation (PCV) Valve, using high octane gas and adding a fuel additive.
Other than that you could either have a damage catalytic converter or faulty ignition control module.

I got this code po 300 but have n o mis fire but I just put a new e c m could that be it

It's possible but not likely. The most common problem for the P0300 with no other symptoms is the ignition coil (s). Let me check if I can find more information, What model and year is your vehicle?