mystery rattle and intermittent stumble

Long story short - ive had these issues for quite some time and have paid thousands at a local shop with no results. I just got a new dp and protune at said shop today and was faced with these issues yet again on my drive home.

 

The rattle - happens at many different rpms, loads, and gears (although not in 1st and 5th). I have a 3" dp and q300 cat(less)back. Are there any tricks I can use to fix or at least locate the rattle? Would temporarily stuffing a ball of heat wrap in various locations help me locate it?

 

The stumble - started before i had my AP. It happens in 2-3k rpm range and under medium loads. Mostly in second gear. My thought was that the exhaust rattle was causing false knock, and causing DAM to go down, thus the stumble. My dam was .812 immediately after the tune. WTF?

 

Usually i have to hold ~1psi boost at 2krpm and the knock disappears and DAM returns to 1. This didnt work for me on my way home. I had to go wot in third for the DAM to return to 1. But there was no fine nock learn on my ap?

 

I want to hear what you guys have to say before confronting the shop about this. Im a little angry that I spent almost 2k and the rattle and DAM issues are still there...

And thats only 2k TODAY! i must have spent double that having them fix boost leaks, replace spark plugs, and ALL coils, without the issues being resolved. >

Not really much we can do help specifically diagnosing the rattle through just text. Perhaps a video may help us. Try getting the car up on a lift/stands, have someone in the car rev it in neutral and see if you can pinpoint where it is. The heat shields on the up-pipe/headers often rust and rattle, that might be a good place to start looking.

 

As far as DAM goes, if it drops, you'll need to do a couple WOT pulls at least for it to return back to 1. Low-loads won't put the car in an area of the ignition map where it will modify the DAM. Any time the DAM changes, the entire FLKC table will be reset to zero.

As far as DAM goes, if it drops, you'll need to do a couple WOT pulls at least for it to return back to 1. Low-loads won't put the car in an area of the ignition map where it will modify the DAM. Any time the DAM changes, the entire FLKC table will be reset to zero.

 

Thanks for the advice on uppipe/header heat shields! i'm going to have a look tomorrow.

another question i have is related to the knock. Is it likely that the tuner would have desensitized the sensor in some way? Or is it more likely he added fuel and the knock is gone?

I highly doubt the tuner would have lowered the sensitivity of the knock sensor (it is possible but it's completely unnecessary), but that's a question to ask your tuner.