Trouble Code P0300

Threw a Service Engine Light today while driving on the highway. Trouble Code P0300 AutoZone said "multiple cyllinder misfire"

Anyone have any info or suggestions?

have you replaced the plugs, plug wires, cap, or rotor lately?

have you replaced the plugs, plug wires, cap, or rotor lately?


fairly recently. I'm leaning towards the simple things first anyways.
cap, rotor, wires, and plugs.

probably should have a diagnostic check to narrow it down.

see my post above yours

fairly recently. I'm leaning towards the simple things first anyways.
cap, rotor, wires, and plugs.

probably should have a diagnostic check to narrow it down.
i had one after i changed my plugs. one of the wires came loose and tripped the code. could be something simple like that. let us know if those check out then we'll go from there.

fairly recently. I'm leaning towards the simple things first anyways.
cap, rotor, wires, and plugs.

probably should have a diagnostic check to narrow it down.

Please supply you recent repair history with the truck.

You have been goign through many other problems so it would be good if you supplied what was done to fix them as well.

As for recently, how recent is the cap, rotor, plugs, wires etc.....

i had one after i changed my plugs. one of the wires came loose and tripped the code. could be something simple like that. let us know if those check out then we'll go from there.

Checked all all the plugs and wires as well as the rotor and even looked for arcs at night. Don't see anything and everything appears to be plugged in well. No maintenance has been done for months aside from an oil change about a month ago.

I would have checked any recent work obviously that may have tripped a code.

Last maintenance performed

(major service) 4/06
Replaced:
fuel spider
regulator
coolant hose
wires
distributor cap and rotor
upper intake gasket
lower intake gasket

All has been fine since then aside from shitty gas mileage (which seems to be the common mileage of our Blazers)

Plugs havent been replaced since Feb of 05 when I'd done a full replacement of cap rotor wires and plugs. I didnt realize that till now. They obviously are due regardless of whether or not thats the problem.

Did you use standard plugs?

If so, I would swap them out seeing they had to under go some shitty service with the gaskets going and the spider dumping gas on them.

They are probably your problem.

Josh, I'm Just passing you some information here to look at and go over, These are some common P0300 problems in our 4.3's......
Good Luck
Dino.................


Injector poppets clog after engine work
Engine is misfiring, possibly on multiple cylinders. Symptoms appear after engine work such as intake or head gasket replacement. In some cases, the engine may not start at all.

Fuel pressure is critical on CSFI systems.
Crank-no-start, low power, surging, rough idle, stalls frequently.
Possible lean codes, possible misfire codes. This tip only applies to vehicles with Central Sequential Fuel Injection (CSFI) or Central Port Injection (CPI, CFI). These systems require high fuel pressures of 55+ depending on year and model. The early '90s 4.3 liter engines needed 55 PSI. Starting in 1996, the 4.3 and the 5.0, 5.7 needed a minimum of 60 PSI to start. Fuel pressure may be slightly lower than 60 while idling, but must be at least 60 PSI to start the engine.

EGR valve sticking open
Possible rough idle and stalling at idle. May set codes P1406, P0404, P1404 EGR Valve Pintle Position Circuit. May also set rich codes or misfire codes such as P0172, P0175, P0300 etc.
NOTE: This tip only applies to vehicles with an electronic EGR valve.

Carbon build-up on injector poppet valves.
Engine misfire, rough idle, possible rich or lean codes. This tip only applies to vehicles with CPI, CSFI, CSI injections systems.

Distributor cap causing misfires and hard start
Engine misfires, especially under a load. In some cases, the engine may fail to start or may kick back while cranking as if timing were off.

Intake gasket internally leaking
Rough idle, misfire codes, lean codes.
Engine runs smoother if the RPMs are raised.

Injector assembly or internal fuel pressure regulator leaking.
The most common symptom is a hard start, long crank after vehicle has been sitting for a short time or over night. Vehicle may run rough for several moments after starting and may have black smoke from tailpipe after start-up. Possible CEL with misfire or rich codes.
NOTE: This tip ONLY applies to vehicles with CPI, CFI, CSFI injection systems.

O2 sensor failures
Engine has a rough idle and misfires. All cylinders on one side of the engine are misfiring. Plugs on one side may be carbon fouled, and other plugs may be ok. May have misfire and/or system lean codes stored. Vehicle may start and idle ok until it goes into closed loop, then begins to run rough.

Light misfire or shudder after injector assembly removal or replacement.
Light misfire, surge, or shudder that may be mistaken as a torque converter shudder. Symptoms appear after the fuel injector assembly has been removed or replaced.

Crank sensor air gap too small
Engine intermittently cuts out or misfires. Possible misfire codes stored. Possible P0335 or P0336 stored.

Did you use standard plugs?

If so, I would swap them out seeing they had to under go some shitty service with the gaskets going and the spider dumping gas on them.

They are probably your problem.

when I did the plugs nearly 2years ago, yes I used the AC Delcos that was reccommended via this site. And you're right. They probably are a little nasty. If nothing else it should improve mileage.

Josh, I'm Just passing you some information here to look at and go over, These are some common P0300 problems in our 4.3's......
Good Luck
Dino.................


Injector poppets clog after engine work
Engine is misfiring, possibly on multiple cylinders. Symptoms appear after engine work such as intake or head gasket replacement. In some cases, the engine may not start at all.
Fuel pressure is critical on CSFI systems.

Crank-no-start, low power, surging, rough idle, stalls frequently.
Possible lean codes, possible misfire codes. This tip only applies to vehicles with Central Sequential Fuel Injection (CSFI) or Central Port Injection (CPI, CFI). These systems require high fuel pressures of 55+ depending on year and model. The early '90s 4.3 liter engines needed 55 PSI. Starting in 1996, the 4.3 and the 5.0, 5.7 needed a minimum of 60 PSI to start. Fuel pressure may be slightly lower than 60 while idling, but must be at least 60 PSI to start the engine.EGR valve sticking open

Possible rough idle and stalling at idle. May set codes P1406, P0404, P1404 EGR Valve Pintle Position Circuit. May also set rich codes or misfire codes such as P0172, P0175, P0300 etc.
NOTE: This tip only applies to vehicles with an electronic EGR valve.Carbon build-up on injector poppet valves.

Engine misfire, rough idle, possible rich or lean codes. This tip only applies to vehicles with CPI, CSFI, CSI injections systems.Distributor cap causing
misfires and hard start
Engine misfires, especially under a load. In some cases, the engine may fail to start or may kick back while cranking as if timing were off. Intake gasket internally leaking

Rough idle, misfire codes, lean codes. Engine runs smoother if the RPMs are raised.
Injector assembly or internal fuel pressure regulator leaking.

The most common symptom is a hard start, long crank after vehicle has been sitting for a short time or over night. Vehicle may run rough for several moments after starting and may have black smoke from tailpipe after start-up. Possible CEL with misfire or rich codes.
NOTE: This tip ONLY applies to vehicles with CPI, CFI, CSFI injection systems.O2 sensor failures

Engine has a rough idle and misfires. All cylinders on one side of the engine are misfiring. Plugs on one side may be carbon fouled, and other plugs may be ok. May have misfire and/or system lean codes stored. Vehicle may start and idle ok until it goes into closed loop, then begins to run rough.
Light misfire or shudder after injector assembly removal or replacement.
Light misfire, surge, or shudder that may be mistaken as a torque converter shudder. Symptoms appear after the fuel injector assembly has been removed or replaced.

Dino, I'm having trouble reading your post. Can you highlight what the topics are that the symptoms are describing? It's really hard to read, and theres no real seperation between its sentences. Thanks

Threw a Service Engine Light today while driving on the highway. Trouble Code P0300 AutoZone said "multiple cyllinder misfire"

Anyone have any info or suggestions?

I asSume it is on your 98 right?
As said go over the basics.
Good ac delco plugs and AC delco cap and rotor and good wires.
Fuel pressure and egr valve check for sure.
If all else fails check the camshaft retard setting with a engine capable scanner.
Also a good scanner should pin point what cylinder and how many miss fires on that cylinder.

I had this very same code with my 2000 Blazer when I went on Vacation Last year. My truck only had 75,000 mile so I decided to tune it up. AcDelco plugs,Dist cap, rotor, wires and still ended up with the same problem. What I ended up doing is buying some Lucus fuel injector cleaner and when I was on the highway I started driving it like I stole it and low and behold It cleaned out the poppets and I never seen the code again. I still add the fuel injector treatment quite regularly and had not had a single problem yet. Knock on wood!!:uhoh:

Josh,
I Edited Post #9 above....

did you look at my post on p0300 and p0141?? check out the distributor sensor itself. it is below the rotor and you must remove the distributor to replace it. i had the dist replaced as there was a little play in the bearings after 130k or so.

the light went off yesterday before making any changes....wierd

my light went out also. codes still there,, no codes since new distributor last week. driving to nyc weds we will see what happens ...

Yes, my light did this too and only happened on hard throttle or high rpms. No code but P0300 from mine but it was the crank sensor that I had replaced with a Wells months before and started getting the random misfires and then high rpm valve rattle so timing was off. Switched crank sensor out for a standard motors one and fixed everything. The newer Blazers are not setup to even check the timing from up top with a light anymore unless someone knows the way?? Again - stay away from Duralast/Wells crap on any ignition products - they always come back and bite you.

Yes, my light did this too and only happened on hard throttle or high rpms. No code but P0300 from mine but it was the crank sensor that I had replaced with a Wells months before and started getting the random misfires and then high rpm valve rattle so timing was off. Switched crank sensor out for a standard motors one and fixed everything. The newer Blazers are not setup to even check the timing from up top with a light anymore unless someone knows the way?? Again - stay away from Duralast/Wells crap on any ignition products - they always come back and bite you.


so what part and what manufacturer fixed your problem?

Do you recommend AC DELCO Platinums, or AC DELCO Rapid Fires?

Crank sensor was a Standard Motors Products one - some come under name True Tech by SMP. Now at Advance the GP Sorenson stuff is owned by SMP but is it as good?? I've gotten a TPS form GP and that worked well. Those Wells parts I now totally stay away from after 3 bad experiences in a row and thats too many for me - who cares if you get a free replacement. Do it once!

As for plugs the main body here seems to say Delco Plats with 1 electrode, the #41-932 but I have used the Bosch Plats again 1 electrode in mine for many years #6241 with not a miss so you decide. Many of the plug problems I believe are related to the older Blazers 95 earlier and mine are all 98up.