Cylinder 1 Misfire trouble shooting...

Ozer · January 10, 2020

2014 Sierra 5.3 with 130k miles now and counting..

New Plugs/Wires/Coils at 120k.

Every couple days i get this misfire coed P0301.

I can tell its coming because the truck starts to idle rough, then it drives like crap, no power.. traction control light comes on (not sure why this is) and the transmission shifts up and down harsh.

The MIL flashes and after few miles everything goes back to normal and truck runs fine again or i clear the codes then its fine. The code is kept in stored codes when i go to delete it.

I pulled #1 plug and it looks perfect, dry no issues. Swapped the #1 wire to #3 and no change. I could swap the coils next but im sure it wont change, they are all new.

Im suspecting an injector issue so i been running cleaners, currently on SeaFoam treatment, next i have Amsoil P.I. going into a 1/4 tank of fuel to have very strong cleaning agent running thru the injectors.

Any suggestions or experience with this?

BigBadSierra · January 10, 2020

There is the possibility that the AFM lifter is starting to fail. This is the code everyone gets when one starts to go.

You seemed to have eliminated the other possibilities.

Ozer · January 10, 2020

13 minutes ago, BigBadSierra said:

There is the possibility that the AFM lifter is starting to fail. This is the code everyone gets when one starts to go.

You seemed to have eliminated the other possibilities.

Forgot to mention, i tuned the AFM out. Truck just runs better and gets better MPG in my case, go figure lol

I went back to it few times and after few weeks i would remember why i turn it off.

TJay74 · January 10, 2020

my money is on a bad DI injector, somewhat of a common issue on the 2014+ DI trucks.

JimCost2014 · January 10, 2020

1 hour ago, Ozer said:

Forgot to mention, i tuned the AFM out. Truck just runs better and gets better MPG in my case, go figure lol

I went back to it few times and after few weeks i would remember why i turn it off.

Have you thought about packing your scan tool with you, so if it starts running rough again, you can hook up the tool and possibly see what is going on?

If you can see real time data, the problem should show itself.

Ozer · January 10, 2020

I have the FOXWELL NT301 which has live data so ill have to leave it plugged in and do some logging to see whats happening. Not sure if it will show me injector pulses and spark? I just got this thing last week.

Ozer · January 11, 2020

This has been happening all day today on and off. I'm starting to think it happens after 8-10 start cycles but need to count then to be sure.
One thought.. If my number 1 injector was clogged, wouldn't I have constant misfire in #1?
My misfire comes on with rough idle, I keep driving, truck shakes and sputters but after a bit the lights go off and it drives smooth as silk. I'm going to compression check this weekend just to make sure cylinder 1 is fine.

So. Weird and frustrating. Not looking forward to taking this into the dealer if it comes to that.

Sent from my SM-N960U using Tapatalk

Doublebase · January 11, 2020

From everything I've been reading it sounds like an injector.

I'm having a similar situation going with cylinder number 5. Not as bad as yours yet, but I'm getting a slight misfire occasionally when going up a hill on the highway. Only one check engine light so far, it cleared up on it's own in minutes. The light flashed. Came on. Then went out, but I did feel the misfire.

I have hooked the scan tool up and see a misfire her... a misfire there on every cylinder on occasion. Looks pretty normal. But twice the cylinder five acted up when on the highway (going up a hill, giving it some gas, etc). 7 misfires once, then 14 the second time.

Fuel trim was in the negative...-24 long term fuel trim. That was checking it after five miles of driving, cold start, probably 20 degrees outside. I wish I had checked it when it warmed up but I was too busy watching the misfire counter. Pulled the spark plug, it looked great. Moved the coil to another plug. Still got some misfire hits on cylinder 5.

But if you are getting the rough idle upon start up...from what I've read that's a sign of the injector.

I'm going to try to run super through it for a few weeks...maybe put a fuel additive in it. Don't think it will help. Cylinder 5 is right under where the PVC valve dumps into the intake. I run a catch can...part of me thinks the cold weather is dumping liquid vapor right into cylinder 5, but I doubt that too.

I have 45,000 miles on my 2018 Silverado 5.3 - not real happy to be honest - expected much more from this vehicle than this. This thing is babied and well well cared for. I'll see how it goes. I'll try to live with it until it gets worse...and who knows? Maybe it won't get worse, but from what I've been reading, these injectors are the real story behind these engines...probably more so than the AFM failures and torque converters. Doesn't look like too bad of a job to do, but when you're in there you might as well do all 8 injectors...what's that going to cost? $480? $600?

Edited January 11, 2020 by Doublebase

Ozer · January 11, 2020

Thanks for that, sounds very similar to mine. Aren't you under warranty? You should take it in when it throws a code and get it replaced.
Going forward run seafoam treatment in the gas to keep them clean.
I'm at 131k miles

Sent from my SM-N960U using Tapatalk

durandetto · January 11, 2020

From everything I've been reading it sounds like an injector.

I'm having a similar situation going with cylinder number 5. Not as bad as yours yet, but I'm getting a slight misfire occasionally when going up a hill on the highway. Only one check engine light so far, it cleared up on it's own in minutes. The light flashed. Came on. Then went out, but I did feel the misfire.

I have hooked the scan tool up and see a misfire her... a misfire there on every cylinder on occasion. Looks pretty normal. But twice the cylinder five acted up when on the highway (going up a hill, giving it some gas, etc). 7 misfires once, then 14 the second time.

Fuel trim was in the negative...-24 long term fuel trim. That was checking it after five miles of driving, cold start, probably 20 degrees outside. I wish I had checked it when it warmed up but I was too busy watching the misfire counter. Pulled the spark plug, it looked great. Moved the coil to another plug. Still got some misfire hits on cylinder 5.

But if you are getting the rough idle upon start up...from what I've read that's a sign of the injector.

I'm going to try to run super through it for a few weeks...maybe put a fuel additive in it. Don't think it will help. Cylinder 5 is right under where the PVC valve dumps into the intake. I run a catch can...part of me thinks the cold weather is dumping liquid vapor right into cylinder 5, but I doubt that too.

I have 45,000 miles on my 2018 Silverado 5.3 - not real happy to be honest - expected much more from this vehicle than this. This thing is babied and well well cared for. I'll see how it goes. I'll try to live with it until it gets worse...and who knows? Maybe it won't get worse, but from what I've been reading, these injectors are the real story behind these engines...probably more so than the AFM failures and torque converters. Doesn't look like too bad of a job to do, but when you're in there you might as well do all 8 injectors...what's that going to cost? $480? $600?

If you do the injectors yourself it might be less than $600. If you have a shop or the dealer do them you're looking at $1500-$2000.

Sent from my SM-N975U using Tapatalk

Ozer · January 11, 2020

I just had a friend with a professional scanner look at it and he was able to see the misfire history but when he was looking at live data, all injectors were working as they should and no misfires were detected.
Only other thing left to do is a compression check on #1.
Could this be a sticking valve?

If it was a clogged injector it should be running rough the whole time with misfires. My issue comes and goes. It was running perfectly on the way to his shop and back.
I'm so confused on what it can be lol ahhhh

Sent from my SM-N960U using Tapatalk

Doublebase · January 12, 2020

17 hours ago, Ozer said:

I just had a friend with a professional scanner look at it and he was able to see the misfire history but when he was looking at live data, all injectors were working as they should and no misfires were detected.
Only other thing left to do is a compression check on #1.
Could this be a sticking valve?

If it was a clogged injector it should be running rough the whole time with misfires. My issue comes and goes. It was running perfectly on the way to his shop and back.
I'm so confused on what it can be lol ahhhh

Sent from my SM-N960U using Tapatalk

Mine is not showing a lot of misfires either, have your friend look at the fuel trim adaptives , both long and short term adaptives. Mine was reading -25. That tells me I have an injector probably leaking a bit and the computer is trying to compensate by taking away fuel. I also turn on the fuel economy portion of the digital readout on the dash and I can see the fuel economy gauge kind of going up, then down...like the computer is trying to correct it.

I really need to keep an eye on this, I don't smell fuel, which is a good thing...and I've pulled my oil dipstick, it doesn't smell like fuel but then again maybe it does? I can't really tell - I do think it's strange that I'm at 5,000 miles of my interval and I'm still at the "full" mark. That never happens, I always use some oil between changes and have to add. Not this time. Makes me wonder if I have fuel in there. I might change my oil today and track it.

Ozer · January 12, 2020

That's a good idea, I'll check my oil. I just changed it few hundred miles ago but now I remember when I drained mine last it was more runny and brown compared to black.
I assumed it was due to the CRC cleaning I just did prior to changing the oil.

I used my scanner while this issue was happening and both fuel trims were in the negatives or said faulty. Timing was high.

When I do the compression check today and it comes out normal then injector has to be it. Not sure what else I can check at this point.

Sent from my SM-N960U using Tapatalk

Ozer · January 12, 2020

I just did the compression check on #1 and #3 for comparison. Was short on time so I wasn't able to do any others.

#1 was 182psi
#3 was 210psi

Not sure what the proper psi on these engines should be.
While I was in there in swapped #1 and #3 cylinder and replaced the #1 coil with another one I had.

Also checked my oil (changed about 500 miles ago after a CRC cleaning) and it looks new so i dont think fuel is being dumped into the cylinder when not running.

Let's see what happens..

Sent from my SM-N960U using Tapatalk

Edited January 13, 2020 by Ozer

Kevin Wright · January 12, 2020

Having the exact same issues. 2017 Sierra z71 crew cab. Truck has 40k miles. Throws codes for misfires and rough idle. Got an email from gmc about a emissions issue. Every so often after pulling out of my driveway, the traction control light will come on and go away. When this happens, the truck will slam down gears from 3,2,1 then surge on take off. It’s hit or miss but frustrating as hell. Truck has been parked for a week. I just scheduled an appointment at the dealer because I’m fed up with this pos. I have a 100k mile power train warranty. Hopefully it’s a simple fix but I’m not willing to dish out any money out of pocket for what is essentially a brand new truck.