Check engine light/ problem code P0300

[STREETutilityVEHICLE]

i had a check engine light on this morning when i started my truck. i live in colorado in the mountains and it's pretty cold. the guy at autozone ran the code reader and came up with a code P0300 and it said something about misfiring. he wasn't the smartest so i wrote the code down and figured i'd ask ya'll i have a 2003 tahoe with a 4.8L in it. anyone know if this just means i need to change my sparkplugs? thanks in advance!

 

[Darkhorz13]

Haynes book is sayin that code P0030 = HO2S heater control circuit bank 1 sensor 1.
Hope that helps get you closer to resolution.

 

[str8wkd1]

this may help
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 SolutionsIf 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.

Other Reading

 

[STREETutilityVEHICLE]

THANKS!!!!!

 

[richardak]

Check Engine Light

I am having the same problem with my 1997 Tahoe 4WD 5.7L. Is there a way that these parts can be tested? I have already changed my plugs, wires, rotor and distributor. I would like to test these other parts before I go out and spend more money.

 

[Darkitec]

I am having the same problem with my 1997 Tahoe 4WD 5.7L. Is there a way that these parts can be tested? I have already changed my plugs, wires, rotor and distributor. I would like to test these other parts before I go out and spend more money.

Similar problem. 03 5.3 flex fuel, Out of no where, on the freeway random misfire and no power.
Finally struggled home, 40 miles or so. Was down to 3 or 4 working cylinders at that point.
Shut off engine, restarted and it was running fine, Until I got about 2k to 2500 rpm then the miss reappeared.
I did have a maf out of range code, so I replace the MAF, figured I should also do the (4) O2 sensors, plugs and wires, just-in-case. Started the truck and ran fine, again until about 2 to 2.5k rpm and miss reappeared. No other codes, I'm stymied. 92000 miles it shouldn't be having this trouble yet.

I have no idea what to look at next. Does anyone have a clue what I can do to find the fix?

 

[KLFER]

this may be to late, but i would say most of the time it is the intake gasket. this is a known problem. i have replaced a lot of these and fixed the problem. just make sure if you buy the gasket set its the updated gasket kit. about a $60 dollar fix.

 

[Grebbler]

this may be to late, but i would say most of the time it is the intake gasket. this is a known problem. i have replaced a lot of these and fixed the problem. just make sure if you buy the gasket set its the updated gasket kit. about a $60 dollar fix.

+1

Also great time to check the knock sensors for corrosion, clean IAC and throttle body. Make sure you have the correct ACDelco spark plugs installed. No Autolite, no Bosche, no arguments.

 

[KLFER]

Little update: My Tahoe just had these symptoms, loss of power, pings and engine light on p0101 MAF out of range and p0300 misfire, so first thing i did was do a power balance test, i unplugged each coil which every one created a miss, i replaced the plugs and wires less then a year ago along with the updated fel-pro intake gasket, used a scan tool to watch my 02 sensors which sensor 2 was bouncing all around so i pressure tested my exhaust before the cat and had almost 18 psi of pressure so i replaced the cats and runs great again. BTW if you buy new cats make sure you find out if you have a low emissions vehicle or not, it does make a difference. i found out the hard way.

 

[BigWheelinBubba]

Back in January I had the same code. Turns out using Seafoam top end cleaner at the same time as running an E85/Gasoline mixture of 30% E85 to 70% gas loosened up a chunk of carbon on cyl. #1 lodging it in the exhaust valve.

Lesson learned: Do not try to remove extreme carbon buildup on a 250k mile engine. :doh:
Put a used engine with 100k on it that I got for $400.