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 "puff" 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.

 

[CrashTestDummy]

Finish replacing the plugs, AND, I'd recommend, a fresh set of plug wires. Our '12 Caprice developed a miss, and after swapping things around and not getting resolution, I threw a fresh set of AC plugs and Delco wires on it. All the codes cleared. This is the first 'modern' car we've owned where plugs/wires would cause a miss, and a fresh set of both actually fixed the issue.

All of the plugs came out looking used, but clean and with good color. The plugs you show in the attachments above look like cr@p!

 

[RET423]

My 2 cents
Your misfire turns off the stabilitrack when it occurs

Your misfire wasn't properly diagnosed

Always move a coil pack to see if the miss moves with the coil pack, if it doesn't leave the coil packs alone

Do the same with the spark plug and wire unless there is something obviously bad, see if the miss moves

If the miss moves you have found the problem & know what to buy, if the miss didn't move, move the injector next & see if the miss moves

If not your problem is in the cylinder and you haven't spent any money yet

Now you check compression but with the white smoke I think your going to have a blown head gasket

 

[dkad260]

That spark plug is terrible looking, no chance on earth it's going to fire. I would definitely perform a compression test on at least Cyl 1&3, then 2&4....and compare.

Do you have a restricted PCV system, maybe a catch can that's clogged?

I agree the white smoke is not a good sign. What does the dipstick look like? Hopefully just oil and not a milkshake.

 

[PBandJs_PPV]

That spark plug is terrible looking, no chance on earth it's going to fire. I would definitely perform a compression test on at least Cyl 1&3, then 2&4....and compare.

Do you have a restricted PCV system, maybe a catch can that's clogged?

I agree the white smoke is not a good sign. What does the dipstick look like? Hopefully just oil and not a milkshake.

This whole thing has me regretting buying this PPV. I've never had a simple misfire not be fixed with a plug alone, in some cases the wire, and in rare cases the coil.

It's chewing through gas like it was free. I can't seem to locate the cause of the misfire. It smells HEAVILY of raw fuel and shakes like it's going through withdrawals.

Here are new details I have. The codes are now:
P0301 misfire #1 cylinder
P0446 EVAP System Vent Control
P0461 Fuel Level Sensor "A" Circuit Range/Performance
P0463 Fuel Sensor "A" Circuit High

The odd thing is that looking at recorded 'live' data from the OBD scanner, I'm not seeing a misfire on #1, but I am seeing misfires on 2, 3, 5, and 7. Sometimes 3. All plugs and wires have been changed on 1, 3, 5, 7, and 2. (NGK G-Power plugs and generic 10.5mm silicone wires)

I cleared the codes, restarted the truck and THE SECOND the CEL comes on, I hear a noise coming from the rear of the truck (thinking it might be the Canister Purge Valve making that whine.) I'm not sure at this point. It is a kind of hum. I can re-create it by clearing the codes and starting the truck up again and waiting less than 30 seconds.

I have also begun to think that it might be a clogged PCV system that is causing the misfire, along with perhaps the Canister Purge Solenoid under the hood.
What do y'all think?? Could it be a partially clogged fuel filter?

I don't want to just throw a flurry of parts at this, but I'm getting desperate enough to start just throwing parts at this thing. And the 'coincidental' fuel gauge failure isn't helping as my wife is having to still drive this thing 30 miles a day to/from work and I troubleshoot once It's cooled down.

When I checked the oil level a couple of weeks ago before this all began, it was just oil, no milkshake.

I also put about 1.5 cups worth of acetone in the tank to 'superclean' the injectors.

 

[PBandJs_PPV]

Finish replacing the plugs, AND, I'd recommend, a fresh set of plug wires. Our '12 Caprice developed a miss, and after swapping things around and not getting resolution, I threw a fresh set of AC plugs and Delco wires on it. All the codes cleared. This is the first 'modern' car we've owned where plugs/wires would cause a miss, and a fresh set of both actually fixed the issue.

All of the plugs came out looking used, but clean and with good color. The plugs you show in the attachments above look like cr@p!

Is using Delco wires recommended? I know plugs can be pretty specific to an engine but wires?

 

[Fless]

P0446 EVAP System Vent Control

I cleared the codes, restarted the truck and THE SECOND the CEL comes on, I hear a noise coming from the rear of the truck (thinking it might be the Canister Purge Valve making that whine.) I'm not sure at this point. It is a kind of hum. I can re-create it by clearing the codes and starting the truck up again and waiting less than 30 seconds.

The evap valve at the rear is the canister VENT valve. The purge valve is in the engine compartment.

Have you looked at fuel trims? If not, take a look at them and post 'em up.

You may want to consider doing the TSB that includes the updated valve cover; maybe @donjetman can point us to what he did.

 

[PBandJs_PPV]

The evap valve at the rear is the canister VENT valve. The purge valve is in the engine compartment.

Have you looked at fuel trims? If not, take a look at them and post 'em up.

You may want to consider doing the TSB that includes the updated valve cover; maybe @donjetman can point us to what he did.

Okay, thank you, yes. I believe the noise is coming from the vent valve. If I had to say, the sound is like a slight suction leak, sort of...

I have historical 'recorded' data. I can post:
Long term fuel % trim - Bank 1
Long term fuel % trim - Bank 2
Oxygen sensor 1 Bank 1 Short term fuel trim (Does not show any data)
Oxygen sensor 1 Bank 2 Short term fuel trim (Does not show any data)
Short term fuel % trim - Bank 1
Short term fuel % trim - Bank 2

Which of these would be helpful?

I have read the TSB info posted by donjetman and fully plan to swap the valve covers ASAP, but I need to locate and address the misfire first.

 

[Fless]

Okay, thank you, yes. I believe the noise is coming from the vent valve. If I had to say, the sound is like a slight suction leak, sort of...

I have historical 'recorded' data. I can post:
Long term fuel % trim - Bank 1
Long term fuel % trim - Bank 2
Oxygen sensor 1 Bank 1 Short term fuel trim (Does not show any data)
Oxygen sensor 1 Bank 2 Short term fuel trim (Does not show any data)
Short term fuel % trim - Bank 1
Short term fuel % trim - Bank 2

Which of these would be helpful?

I have read the TSB info posted by donjetman and fully plan to swap the valve covers ASAP, but I need to locate and address the misfire first.

All of those would be helpful to see, especially if we can tell what the engine rpms were at the time of the snapshot.

 

[PBandJs_PPV]

All of those would be helpful to see, especially if we can tell what the engine rpms were at the time of the snapshot.

File is too large. May I email it to you?

 

[Fless]

File is too large. May I email it to you?

See if you can attach it to a PM (Start a Conversation)