Hesitation/Stumble + Buzzing - TehSpud’s Wagon is haunted

[tehspud]

It’s time to create its own post for this. 

 

My 05 LGT has been doing a weird hesitation/stumble/stutter, what have you on mid to heavy throttle between 3k-4k rpm. If I stay out of it it’s fine. At first I thought it was bad gas but it’s stayed through a couple of tanks. From my AP, DAM has stayed at 1, AFR is going to 11 above 3k, no other readings that say something is going poorly. I’ve tried getting a log, but a lot of the time when I try and recreate this behavior, the AP acts like it loses power/connection to the car in the middle of it. You can almost see this happen in the video, especially if you slow it down. 

 

Video of stumble:

https://youtu.be/zJ3N5m1GJjU

 

The blinking code is a Cyl 1 misfire. I’m waiting on a new coil pack, and it’s too hot today to go back out and swap it around to see if it is actually the coil. 

 

To add to this, starting yesterday afternoon, it is now making a buzzing (?) sound around 3k RPM. Again, too hot today to go out and pull the dp to check turbo health. I drove to work yesterday without this sound, it sat all day, then driving home it started doing this. 

 

Video of buzzing:

https://youtu.be/LY8QC4EMloo

 

I’m guessing it’s new engine time, but I’m hoping the long time owners can identify some of these problems.  

[rhino6303]

Sounds like a boost leak.

[tehspud]

32 minutes ago, rhino6303 said:

Sounds like a boost leak.

Edit: Sorry, I read that as vacuum leak. Boost leak would only exist between the turbo outlet (cold side) and the throttle body, yes? 
 

 I pulled the IC and checked the lines a couple nights ago, everything is plugged into where it should be. I haven’t gone as far as doing the soapy water test. 

Edited July 22, 2023 by tehspud

[tehspud]

Buzzing was 100% the throttle body coupling hose not being fully on the intercooler. Re-seated it and that part is gone. I don't really have the means to be doing a vacuum leak test on my own; My only source of air in the garage is a 12v tire pump. So I'm probably going to call a local shop to get them to do some testing to find it. 

[seanyb505]

Sounds like that could also be some of the leak. I know you're waiting to swap in a new coil, but have you driven it yet? 

Edited July 24, 2023 by seanyb505

[tehspud]

3 minutes ago, seanyb505 said:

Sounds like that could also be some of the leak. I know you're waiting to swap in a new coil, but have you driven it yet? 

Yeah, drove into work this morning and gave it some beans to see, and it's still exhibiting the same behavior from the first video, without any CEL flashing. Coil arrives today.

Should be getting some reprieve from the 95+ deg heat starting tomorrow, so I might be able to rig something up to do Max's suggested "block off the after-MAF hose, blow air into BOV little hose" test. Hopefully the 12v tire pump is enough pressure for that? 

[tehspud]

Got cyl #1 coil changed out yesterday evening, and so far no more hesitation like in the first video, and boosted to 15psi (cobb stg 1)

so either:

a) it was the coil going bad

or

b) There was a leak somewhere between the airbox and the turbo inlet that I fixed in taking those parts off & putting back on to get to the coil. 

 

Gonna give it a couple of days of driving and pulls in 3rd/4th to see for sure before I officially say it's fixed, though.

Edited July 27, 2023 by tehspud