This!!!!!!! It is misfiring. Assuming the new plugs are gapped properly it is likely a coil pack.

 

Are you tuned? Without a tune I had this problem with the airbox mod and my CAI.

 

There is a "knock safety" rev limiter, but if you are getting enough knock to cause that then there is a problem that they should be fixing. I am going to say it is probably the old coil pack going bad, but it could also be a fuel problem as well.

 

This is similar to what Ive been having going on. My car runs and drives fine in stock mode, I can get to 7K cleanly!! When I switch the tune on I hit a wall around 5800 and it almost sounds like misfiring and the car noses over. The logs are clean, trims are on, 0 KR when it happens!! I just go my new coil packs in the mail today, going to test them out tonight hopefully. Def seems spark related!

 

Let us know!!!

 

These are the EXACT symptoms that occur when you try driving the car without a MAF sensor, though that should throw a code. Swap with someone else's MAF and see if the problem is still there.

 

I also ordered a MAF and new purge solenoid. I didnt have time tonight to check the coil packs out, I will tomorrow tho!

 

They've had it for 4 days now and they can't find the issue. I've had 3 techs look at it including a 25year tech...nothing zip none

It's so annoying I've had it on diagnostics over n over no code thrown. It's like finding a needle in a hay stack imo

 

I haven't messed with mine yet, sorry!! I have the coil packs sitting there and the wife is out tonight with my daughter. Im hoping to test them out tonight quick and either that's the fix or rule it out. I just changed plugs within 500miles but I have a 2nd set of new ones to test anyway also. My MAF and Purge solenoid should be here tomorrow but this weekend is packed solid (in a wedding) so Im not sure I will get to try those out

Ill post back when I do or hopefully you're dealer figures it out too lol!

 

they didnt fix it. i am picking it up tonight may just do a aftermarket tune and see if that fixes it

I have the exact symptoms my friend...pulls so hard and then bam! Hits a wall of f u!

 

Well, I replaced the coil packs last night with no change. Then tried the Purge Solenoid and new MAF also with no change.

 

But I thought they'd narrowed it down to a secondary rev-limiter, bunch of asshats . Has GM sent a technician on-site from headquarters to take a look, or are these technicians in the garage on the phone with GM Tech (sorry if you had posted it and I missed this part)?

 

Is fuel pressure good? Maybe the wastegate is opening when it shouldn't be?

 

So then what could it be? does this only occur with ur aftermarket tune? I am still on OEM tune man

Thats what they thought it was, but everyone that owns one can say that they dont have this issue, except a couple. I say i didnt want the car back until it was fixed. I got into a arguing match with the "25yr tech" that says he knows it all could not find a problem. they had it on their diagnostics and what not they couldnt find anything, thats the only thing they did, they also phoned GM and they told him that the rev limiter is set at 6300 so i said screw it and i said ill pick it up "thanks for nothing" *click*

No clue I have no way of testing while doing pulls unless osmeones in the car with me on a HPT. the wastegate sound is evident while it is spuddering and back firing

 

Read this carefully..then start to explore some possible sources of the problem:

http://www.2carpros.com/how_does_it_work/backfire.htm

BTW, I think either FUEL (lean) interuption or a VACUUM (boost) leak could be the problem.
Good luck and I hope this helps...

 

As i posted on HPTuners forum, im having the same problem. I do notice in my logs that VE airflow pegs about 67lb/min which is a lot higher than expected of less than 40lb/min. Hoping this might give insight.

 

So someone else had their VE airflow read 67lb/min. It was because their MAP sensor was blown. I ordered a new one (stock not staged) from my local dealer for $70, picking it up tomorrow morning and will report results once installed.

 

So they now have egg on their faces, what a pain in the ass. Any other dealers you could try in your area and demand they get GM Tech on the phone/into the dealer to help diagnose the problem and get it resolved?

 

if it a weak coil and causing misfire try to gap the plug closer gap them at .010 whit that it will run bad at idle but under full trottle if it ok the problem whent away it a bad coil or bad ignition system

most people at the gm dealer dont know nothing about performance

 

Any updates? Seems like there are quite a few of us having similar problems, but cannot find the solution!

 

VE airflow pegs at 67 lbs/min when the compressor surges.

 

i was not experiencing surge at that time, and even during my worst surging, VE airflow never pegged 67lbs/min or anywhere near it.

 

my guess would be a lift pump, which is starving the Injection pump.

 

No updates as of yet. car still runs the ***** i was on vacation for a week so it just sat in the drive way.

 

replaced MAP and TMAP sensors. No longer see VE airflow hit 67lbs/min... but car still acts goofy up top. Thats my 2 cents (+ $95 for the stage sensors). Would be great if somebody growing a money tree in the backyard could figure this out...