Dreaded P0300, need help!

[Texasbirdslive]

I have a 2013 Tahoe LS 5.3. It is misfiring severely. I changed out plugs, wires, MAF, Throttle position sensor and evap unit on motor. I also changed out the up and downstream ox sensors on drivers dies due to codes. Sounds like I'm throwing parts at it but I'm not. LOL It sputters and back fires. It not the tranny because it does this at idle. I am mechanically able just no luck. Today I ordered Autel scanner today. Any suggestions? I hate the dealership but I might be time to take it in.

Joe

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

If possible, wait to the Autel scanner to arrive before engaging the dealer. You have a good chance of identifying the source of your issue with the scanner. Also, posting what the scanner has to say will help other members of this Forum to assist you.

 

[Doubeleive]

I have a 2013 Tahoe LS 5.3. It is misfiring severely. I changed out plugs, wires, MAF, Throttle position sensor and evap unit on motor. I also changed out the up and downstream ox sensors on drivers dies due to codes. Sounds like I'm throwing parts at it but I'm not. LOL It sputters and back fires. It not the tranny because it does this at idle. I am mechanically able just no luck. Today I ordered Autel scanner today. Any suggestions? I hate the dealership but I might be time to take it in.

Joe

you did that backwards,
scan first then throw parts......
have you swapped coils? does the problem follow?
how many miles?
done a backpressure test?
fuel pressure test?

 

[Texasbirdslive]

Changed out the fuel pump yesterday, yes it was weak. I thought for sure it was the issue. I used the blue driver scanner initially but was mediocre at best to diagnose the issue. 142000k miles. Synthetic oil, doubt its the AFM. I used a fuel gauge on the rail. I also purchased a smoker to see if it was an evap issue. Last year changed out the charcoal canister. Seems that were I initially started having issues. Need a lifeline.


I know this site is free but Ill throw in a 50.00 dollars amazon gift card who ever can help me solve the issue. Its not much but something.

 

[Fless]

No matter what you said about it, stop firing the parts cannon -- that's just introducing unnecessary variables into a thorough diagnosis. Save your old parts and, unless what you installed were Genuine GM parts, reinstall them after -- or even before -- the diagnosis.

When you get your scanner, check the individual cylinder misfire counts and post them up.

 

[Texasbirdslive]

No matter what you said about it, stop firing the parts cannon -- that's just introducing unnecessary variables into a thorough diagnosis. Save your old parts and, unless what you installed were Genuine GM parts, reinstall them after -- or even before -- the diagnosis.

When you get your scanner, check the individual cylinder misfire counts and post them up.

Will do. Kept all the parts.

 

[dkad260]

You said backfiring......popping back through the intake?

What was the sequence of events?

Did you get the P0300 first then try swapping parts, or did you do any type of maintenance/repair then the P0300?

Did you use OE AC plugs?

 

[dkad260]

Check your air filter for any rodent damage and make sure the filter is still intact. The reason I say that is because it's backfiring and I assume through the intake, maybe something got sucked in there and is stuck on top of the intake valve.

To check the exhaust valve, take an envelope and hold it against the tailpipe while the engine is running and let the flow of air push the envelope away. If it sucks back hard to the tailpipe tip then you might have an exhaust valve hanging open.

P0300 is a random misfire and has not narrowed down a cylinder yet. This can be the cause of using incorrect parts which is why I asked if you changed anything beforehand..or could be a coil going bad.

 

[Texasbirdslive]

So I received the scanner. Showing misfires in cyl 2 and 5. Still learning how to use it.

 

[rdezs]

Have you sprayed around the intake runners and injectors with some brake cleaner to detect any vacuum leaks? Quick and inexpensive to check.

 

[dkad260]

@Texasbirdslive. What was the sequence of events? Was the misfiring before or after the plug change?

 

[Doubeleive]

So I received the scanner. Showing misfires in cyl 2 and 5. Still learning how to use it.

swap coil's #2 & #3 see if the misfire stays on 2 or moves to 3
also what is the engine running fuel pressure?, if it is not a hybrid then it should be right around 43/44 42minimum

 

[Texasbirdslive]

Solved. Cheap ngk spark plugs from amazon. #8 wasn't bad since ive changed it twice in a year. Definitely needed the fuel pump too.

Now to the a/c not cold enough.

 

[Texasbirdslive]

I moving to hvac section. Thanks.