PULLING MY HAIR OVER A P0301 code!!

[PBandJs_PPV]

I've asked this in the standard Tahoe thread but thought better of it and decided to ask fellow PPV owners for some much needed advice.

I have a pretty new to me 2014 PPV that has run well until this last weekend.

I was simply idling while my wife found a location on her Waze app. Upon accelerating, one of the rear tires slipped a little and BAM, instantly got the CEL on for Check Engine, Traction Control, and Stabilitrak along with a noticeable miss in the engine.

We scrapped our plans and drove the almost hour back home. It was late so I opted to start messing with it until the next morning. The next morning I took her to our local Auto Zone to get the codes read. The only code it came up with was P0301 so I bought a spark plug and coil and went home to replace them. After replacing them, nothing changed. Still missing on #1 and traction control is sometime OFF without any choice and sometimes, I can hit the button and it will go to the ON position but quickly go back to OFF once I try to drive her.

I've bought an 8-pack of plugs and started just replacing them in hopes that maybe there was another cylinder missing that hadn't registered a code yet. No change, but I've only replaced 3 plugs so far.

Another thing I have since found out is that these engines have AFM but I'm wondering. Do PPVs have the AFM disabled for police patrol use or is it active? If it is disabled, is it possible that cyl1 AFM enabled itself somehow? How can I check?
Another thing I've read is that it's possible the PCV valve and tube are part of the AFM system and if so, is it possible the PCV or tube are clogged and causing this? Camshaft and/or Crankshaft position sensors?

I REALLY NEED some help guys! I'm mechanically inclined but this is above my knowledge level. I have it understood from donjetman (and read his suggested write-ups) on the updated valve covers available for this engine and plan on getting them but that won't help my engine miss.

I don't want to keep throwing parts and money at this engine. I would appreciate some real world experience in troubleshooting and fixing this. Can anyone suggest a GOOD APP for reading codes on a phone or iPad? I've got an OBD2 scanner arriving today. What scanned data will best help you help me.

A couple things of note but may not be related:

The last couple of weeks, once in a while. Turning the key would do nothing but generally on the 2nd or 3rd try, she would crank.
In the last week, I believe I've heard a little "****" just as the engine shuts off and I'm not at all sure what that is.


Thank you and sorry for the long read.

 

[mikez71]

Your PPV still comes with AFM unfortunately.
To check them, you can remove your valve covers and make sure the rockers aren't loose.

Might be worth doing a compression check since it's still missing after a new plug.
Did you swap spark plug wires as well?

 

[PBandJs_PPV]

Your PPV still comes with AFM unfortunately.
To check them, you can remove your valve covers and make sure the rockers aren't loose.

Might be worth doing a compression check since it's still missing after a new plug.
Did you swap spark plug wires as well?

I was in a hurry and I F'd up!

I started replacing all the plugs and wires. Had replaced 1, 3, 5, 7 & 2 and planned on doing the remaining 3 after I went and picked my wife up from work BUT forgot to plug the connector that is right next to #1 (Photo 1) and started the truck up. Suddenly noticing that my fuel gauge is reading E when the truck had and was reading 3/4 earlier.
I immediately shut the truck off and plugged that little connector back in but the fuel gauge is still reading empty when I started the engine back on and the low fuel warning came on.

I ran codes and now have THREE new codes! (Photo 2)

And to add insult to injury, the misfire is still present!

 

[j91z28d1]

that's your coolent temp sensor. I've left it off before too. never hurt anything

I'm not sure how that would effect the other sensors and set codes unless you have some wiring issues?

 

[PBandJs_PPV]

that's your coolent temp sensor. I've left it off before too. never hurt anything

I'm not sure how that would effect the other sensors and set codes unless you have some wiring issues?

Then that is one crazy ironic coincidence.

 

[PBandJs_PPV]

Here's where I currently sit:

Swapped out #1, 2, 3, 5, 7 spark plugs and wires. Went with NGK plugs and 10.5mm 'Performance' wires.
The misfire still exists and is all over the place now. If I'm interpreting the OBD data correctly, I've got misfires on 2, 3, 5, & 7 although NONE of those actually show up if I run codes. Only a pending cyl 1 misfire shows but doesn't actually pop. Putting a new 'test' coil on 2 made no difference.

The oddest change I have noticed. When I drove it to pick my wife up from work, she was WAY spunkier. Like, the new plugs and wires on the above mentioned cylinders WAS making a performance increase but [something] is still causing the misfires. So now I'm considering swapping out the cam and crank position sensors and see if that makes any difference.

I'm really close to taking this Hoe to a mechanic and walking away until I've got a submissive hoe again. But before I do, I'm going to go through as much as my skill level will allow.

Any ideas, suggestions, or theories are welcome.

(Including screenshots from the OBD scanner, CarScanner ELM OBD2)

 

[kbuskill]

Those plugs look pretty awful.

I would take one step at a time, finish installing the rest of the plugs and wires to complete that portion of the tune up, then clear the codes and see where you are at.

It could be a dirty fuel injector causing the misfire on #1, or it could be a burnt valve or bad lifter or wiped cam lobe or???

A compression test would be the next thing I would do after replacing the rest of the plugs and wires. If the compression test comes back normal then I would maybe try swapping one of the other fuel injectors with #1 and see if your misfire changes location.

 

[PBandJs_PPV]

Those plugs look pretty awful.

I would take one step at a time, finish installing the rest of the plugs and wires to complete that portion of the tune up, then clear the codes and see where you are at.

It could be a dirty fuel injector causing the misfire on #1, or it could be a burnt valve or bad lifter or wiped cam lobe or???

A compression test would be the next thing I would do after replacing the rest of the plugs and wires. If the compression test comes back normal then I would maybe try swapping one of the other fuel injectors with #1 and see if your misfire changes location.

I am now thinking it's an injector. After the vehicle has been sitting and you start it, a large plume of white gray smoke comes out of the tailpipe and I'm getting a strong raw fuel smell.

I'm going to perform a resistance check on the injectors and possibly even replace the #1 injector and see where that leads.

 

[Fless]

Compression test all the way around? Injector balance test?

 

[RichardCranium]

I am now thinking it's an injector. After the vehicle has been sitting and you start it, a large plume of white gray smoke comes out of the tailpipe and I'm getting a strong raw fuel smell.

I'm going to perform a resistance check on the injectors and possibly even replace the #1 injector and see where that leads.

With what you've gone through this is my suspicion as well.