PULLING MY HAIR OVER A P0301 code!!

[PBandJs_PPV]

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

Nope, think I'll upload it and share it.

 

[PBandJs_PPV]

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

screen-20250515-114447.mp4

drive.google.com

Did it work for you?

 

[TollKeeper]

If I am remembering my LS PCM data correctly, when the PCM detects a missfire, it balance checks that missfire against its batchfire neighbor. Now I dont remember the batchfire neighbor for Cylinder 1 (I wanna say 8?????), but I would also be checking that whatever that cylinder is.

The bad part about Cylinder 1, as has already been mentioned, is that its AFM/DOD.

Have you pulled the valve cover to check for rocker play? Thats the best way I have found to diagnose AFM/DOD issues. You would need to check all the cylinders that have AFM/DOD. My last GM had a DOD/AFM failure on cylinder #1 intake.

Its free to pull the valve cover and check those rocker bridges.

With the white smoke out the tail pipe, I would be leaning to doing the drivers side valve cover update. When they start sucking in oil and whatever thru that valve cover, its a heavy white sickening smoke. Doing the valve cover is a LOT easier than pulling a head. This would also explain why your old spark plugs are so oil coked.

 

[Fless]

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

The link to the mp4 file you posted does work. Note that TYF doesn't host videos, but gives the incorrect error that the file is too large.

 

[PBandJs_PPV]

If I am remembering my LS PCM data correctly, when the PCM detects a missfire, it balance checks that missfire against its batchfire neighbor. Now I dont remember the batchfire neighbor for Cylinder 1 (I wanna say 8?????), but I would also be checking that whatever that cylinder is.

The bad part about Cylinder 1, as has already been mentioned, is that its AFM/DOD.

Have you pulled the valve cover to check for rocker play? Thats the best way I have found to diagnose AFM/DOD issues. You would need to check all the cylinders that have AFM/DOD. My last GM had a DOD/AFM failure on cylinder #1 intake.

Its free to pull the valve cover and check those rocker bridges.

With the white smoke out the tail pipe, I would be leaning to doing the drivers side valve cover update. When they start sucking in oil and whatever thru that valve cover, its a heavy white sickening smoke. Doing the valve cover is a LOT easier than pulling a head. This would also explain why your old spark plugs are so oil coked.

Sigh... I was dreading having to take the cover off, but in reality, I will KNOW either way at that point.
I'll at least remove the question mark in my head.

 

[TollKeeper]

Of all the jobs on the LS engine platform to do... Taking the Drivers side valve cover off is easily in the top 10 easy jobs to do. Likely all of 10 minutes, maybe 20?

Pull the 4 plugs wires off the coils, no need to take them off the plugs.
Remove vacuum line going to PCV, and set aside.
Unplug the main coil harness.
Remove the nuts holding down the ignition coil bracket.
Remove the Coils with attached bracket.
Unbolt the valve cover
Remove valve Cover.

And generally speaking, the valve cover gasket can be reused if its not dried out, and broken.

Now if we were talking about the passenger side... that one is a pain.
But it is easier on the Full Size GM platform.
Royal pain in the ass on the MidSize GM Platform (like the Envoy/Trailblazer)

 

[PBandJs_PPV]

Of all the jobs on the LS engine platform to do... Taking the Drivers side valve cover off is easily in the top 10 easy jobs to do. Likely all of 10 minutes, maybe 20?

Pull the 4 plugs wires off the coils, no need to take them off the plugs.
Remove vacuum line going to PCV, and set aside.
Unplug the main coil harness.
Remove the nuts holding down the ignition coil bracket.
Remove the Coils with attached bracket.
Unbolt the valve cover
Remove valve Cover.

And generally speaking, the valve cover gasket can be reused if its not dried out, and broken.

Now if we were talking about the passenger side... that one is a pain.
But it is easier on the Full Size GM platform.
Royal pain in the ass on the MidSize GM Platform (like the Envoy/Trailblazer)

I'll need to be more cautious doing the valve cover. When I was reaching to get at #7, I lost my balance and essentially used the fender (where it meets the hood) to spread a pair of ribs apart. I'm STILL recovering from that.

 

[dkad260]

How much fuel pressure do you have? Low FP would result in more of a dribble of fuel into the cylinders than a fine mist....but would be more evident on all cylinders.

A faulty injector or a clogged screen could also cause issues. I recently had my injectors rebuilt and flow tested, the baskets looked far worse than I ever expected. I never thought they would break apart like they did. I was chasing erratic fuel trims and this cleaned it up, but I wasn't having misfires either. Just an idea of what can happen and could have gotten worse over time.

I think you may have other issues, but the fact the plug is caked could be from a very rich fuel charge, coolant, sucking oil....I'm just reiterating what others have said.

Definitely do a compression test on Cyl 1, along with inspecting under the valve cover.

 

[kbuskill]

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.

I am still confused why you haven't replaced the plugs and wires on cylinders 4, 6, and 8?

I have never even thought about doing a partial tune up. That would be like saying, "Well, my left front shock with 100k miles is leaking, I guess I better replace that ONE", knowing full well that the other 3 have the same mileage on them. Especially after seeing what those plugs looked like.

Just FYI, the coil bracket harness, that goes between the coils and the engine harness, have been known to go bad and cause misfires.

Have you verified you are getting spark at the plugs?

Also, depending on how much fuel was in the tank at the time, 1.5 cups of acetone probably isn't enough to do much cleaning, especially if the tank had any substantial amount of fuel in it.

 

[PBandJs_PPV]

I am still confused why you haven't replaced the plugs and wires on cylinders 4, 6, and 8?

I have never even thought about doing a partial tune up. That would be like saying, "Well, my left front shock with 100k miles is leaking, I guess I better replace that ONE", knowing full well that the other 3 have the same mileage on them. Especially after seeing what those plugs looked like.

Just FYI, the coil bracket harness, that goes between the coils and the engine harness, have been known to go bad and cause misfires.

Have you verified you are getting spark at the plugs?

Also, depending on how much fuel was in the tank at the time, 1.5 cups of acetone probably isn't enough to do much cleaning, especially if the tank had any substantial amount of fuel in it.

Honestly, it's the matter that they are in a tougher place to get to and I'm limited in regards to time because I work on it after my wife had gotten home and it's cooled down and if there isn't any other family stuff to do. Plus, I messed up my ribs reaching #7 and it took a good four days to get over that pain.

Daughter is home from college so wife is going to drive her car so I can have at the Tahoe without needing to have it available to drive.

 

[PBandJs_PPV]

Update:

Yesterday, the fuel gauge just randomly started working again so obviously there's a loose connection somewhere.

Also, and this sounds REALLY dumb but, I JUST NOW actually looked at the gas cap. I hadn't noticed that fuel requirement and warning. I've just been pumping low grade unleaded from Sam's.
Is this affecting anything?

 

[j91z28d1]

87 should be OK but since you have an issue, if you have a e85 station, you might try some and see how it goes.


on that note do you have a scanner that can read alcohol percentage? these flex trucks use the o2 sensors to try and guess the alcohol % so you can use e85. it more volume than gas to run right. some times the ecm math messed up and thinks you're running E when you're running not making them run super rich. a decent scanner can read what the ecm thinks is in the tank, and if not correct you can reset it.

 

[Fless]

You may use regular gas (87 octane or higher) or E85 (85% ethanol, not available everywhere), or combinations of both mixed. You have a Flex Fuel vehicle, unless the fuel filler cap was changed by mistake. What is the 8th digit of your VIN?

 

[PBandJs_PPV]

87 should be OK but since you have an issue, if you have a e85 station, you might try some and see how it goes.


on that note do you have a scanner that can read alcohol percentage? these flex trucks use the o2 sensors to try and guess the alcohol % so you can use e85. it more volume than gas to run right. some times the ecm math messed up and thinks you're running E when you're running not making them run super rich. a decent scanner can read what the ecm thinks is in the tank, and if not correct you can reset it.

Another curiosity is that the OBD port is hot sometimes. Even with the truck off, I can sometimes connect to the OBD reader and the truck although, as it's off, there aren't any readings obviously. Unless I am truly losing my mind over this.
The 8th digit is a 0

 

[PBandJs_PPV]

87 should be OK but since you have an issue, if you have a e85 station, you might try some and see how it goes.


on that note do you have a scanner that can read alcohol percentage? these flex trucks use the o2 sensors to try and guess the alcohol % so you can use e85. it more volume than gas to run right. some times the ecm math messed up and thinks you're running E when you're running not making them run super rich. a decent scanner can read what the ecm thinks is in the tank, and if not correct you can reset it.

 

[Fless]

Another curiosity is that the OBD port is hot sometimes. Even with the truck off, I can sometimes connect to the OBD reader and the truck although, as it's off, there aren't any readings obviously. Unless I am truly losing my mind over this.
The 8th digit is a 0

So, the LMG, flex fuel.

 

[dkad260]

I've just been pumping low grade unleaded from Sam's.
Is this affecting anything?

The yellow gas cap indicates you can also use E85 if you choose, not a requirement.

However, if not a flex fuel vehicle this could be an issue as the engine requires much more fuel when using E85, the injector flow rate is increased. I doubt this is the problem though but yes, double check your VIN.

 

[Rick Fazz]

Another curiosity is that the OBD port is hot sometimes. Even with the truck off, I can sometimes connect to the OBD reader and the truck although, as it's off, there aren't any readings obviously. Unless I am truly losing my mind over this.
The 8th digit is a 0

Pin 16 should always have B+, required by OBDII standards. You can check with a test light or volt meter.

I've seen pushrods bend when traction is lost. Pull valve cover.
Have you done a visual inspection of wires and hoses from the rear? Sounds to me like a bunch of things started at once,
I would be looking for a common cause.

Fuel gauge sending units are a common problem, on mine once the level goes below 1/4 tank it stops working.

 

[PBandJs_PPV]

OBD Data Dump 01

 

[PBandJs_PPV]

Video

VID_20250517_124728591.mp4

drive.google.com