2013 6.2 starts rough then smooths out for rest of day

georgerosen06 · September 23, 2019

Good morning gm-trucks.com!

I'm having an issue with my 2013 Yukon with the 6.2 engine. For the past month or two the first start of the day will be rough, after that it's fine for the day, no issues. Next morning, rough start again and after the first rough start it goes back to running fine. Any tips on what i should look at? Truck only has around 50k miles on it and is due for an oil change, but not overdue. Only add on is a airraid tube, fram air filter. I took a video of the truck starting and it sounds like it has a nice cam in it...but it doesn't link to the video with sound is below. Any help would be greatly appreciated! Thank you!

https://i.imgur.com/zQh1UJx.mp4

Mikebtte · September 23, 2019

You could clean the MAF sensor and see if it helps.

georgerosen06 · September 23, 2019

12 minutes ago, Mikebtte said:

You could clean the MAF sensor and see if it helps.

I'll give it a shot and let you know how it turns out! Thank you!

georgerosen06 · October 1, 2019

Tried cleaning the MAF and throttle body and still having the rough start, it’s actually getting worse. Took another video of how it’s been the past few starts. Any idea if it’s just bad fuel, or maybe a sensor? Possibly something in the fuel pump/injectors? Any insight or help would be greatly appreciated. Thank you!

https://imgur.com/a/irAupsQ

Mikebtte · October 1, 2019

You could check fuel pressure. If you have bad pressure you would for sure have low power.

This system has no fuel filter so it's worth checking.

Systems alcohol sensor could also be sensing it has a different fuel than is running.

Edited October 1, 2019 by Mikebtte

swathdiver · October 2, 2019

On 9/23/2019 at 9:38 AM, georgerosen06 said:

Good morning gm-trucks.com!

I'm having an issue with my 2013 Yukon with the 6.2 engine. For the past month or two the first start of the day will be rough, after that it's fine for the day, no issues. Next morning, rough start again and after the first rough start it goes back to running fine. Any tips on what i should look at? Truck only has around 50k miles on it and is due for an oil change, but not overdue. Only add on is a airraid tube, fram air filter. I took a video of the truck starting and it sounds like it has a nice cam in it...but it doesn't link to the video with sound is below. Any help would be greatly appreciated! Thank you!

https://i.imgur.com/zQh1UJx.mp4

Mine does that, cranky at start up then runs like a top. Nothing wrong with it at all and I have that Tech-2 to check on things too!

Do you run 87 octane all the time? Try a few tanks of E85 or 93 from a top tier station. Those little bottles of walmart SuperTech fuel injector cleaner work too.

georgerosen06 · October 2, 2019

19 hours ago, swathdiver said:

Mine does that, cranky at start up then runs like a top. Nothing wrong with it at all and I have that Tech-2 to check on things too!

Do you run 87 octane all the time? Try a few tanks of E85 or 93 from a top tier station. Those little bottles of walmart SuperTech fuel injector cleaner work too.

I plan to check the fuel pressure today but thinking about getting a can of bg44k injector cleaner to run through it as well. I’m hoping it’s something simple, but time will tell! Thanks for your input!

edit: just saw the fuel question. I fill it with premium from shell or Valero.

Edited October 2, 2019 by georgerosen06

georgerosen06 · October 2, 2019

So checked the fuel pressure this afternoon and it was at about 40-50 With the key in the accessory position and then bouncing around from 50-65 when running. I think I read that’s normal? I’m going to leave the pressure gauge connected overnight and see if it drops.

georgerosen06 · October 3, 2019

Pressure gauge is already at 0 after only 3-4 hours. I’m assuming that means my problem is a leaking injector or a bad check valve in the fuel pump? Any ideas?

davester · October 3, 2019

50-65 psi doesn't sound good (too wide of a range), but I don't know specifically about your engine. For my port-injected 6.0L LQ4, it expects right around 60psi, +- 3, and the pressure only drops a bit when the engine is revved up, and quickly returns to full pressure.

Before I replaced my fuel pumps, the fuel pressure would be 60 psi at idle, but when the engine revved up, the pressure would drop and stay low. The pcm would try to compensate by keeping the injectors open for longer, but having the proper fuel pressure makes the system work much better.

swathdiver · October 4, 2019

On 10/2/2019 at 10:31 PM, georgerosen06 said:

Pressure gauge is already at 0 after only 3-4 hours. I’m assuming that means my problem is a leaking injector or a bad check valve in the fuel pump? Any ideas?

It's not supposed to drop more than 5psi after one minute. Fuel Pressure should be between 50-60 psi, the proper way to test is to turn key on, engine off and use Tech-2 to command fuel pump relay on and observe pressure. You can ohm test the injectors and with a bi-directional scan tool run an injector balance test.

Silver62 · October 7, 2019

Hope you find out what it is. Mine is doing the same thing 12 Sierra with 6.2 73k miles but mine also has a weird idle. It’s not like a miss but more of a stubble and you can feel it every few seconds while sitting idle. Does yours idle fine? I’ve taken mine to the dealer and described the problems I’m having and they hooked up the tech 2 and told me everything looks fine and the 6.2s just have a bad idle which i don’t think is the answer to my problem

sefiroxx · October 7, 2019

Had the same problem with 01 5.3 burb. Required a little gas until warm up. Had cleaned everything, temp sensor, maf etc. Eventually replaced the isc to fix the problem.

Gagliano7 · October 8, 2019

21 hours ago, sefiroxx said:

Had the same problem with 01 5.3 burb. Required a little gas until warm up. Had cleaned everything, temp sensor, maf etc. Eventually replaced the isc to fix the problem.

What is ISC?

sefiroxx · October 9, 2019

Idle speed control. Mine is a drive by cable, so the isc is used to hold butterfly open on idle.

Yours is drive by wire. The module that contains. On the throttle body is the tps/tac motor. The tac controls the opening of the butterfly based on input from the pedal and the e cu (when cold).

Try cleaning the throttle body/butterfly. Google on how to test gm electronic throttle body.