The Car: 1999 Camaro Z28, mostly stock. Lid and long tube headers.

My problem:

The car runs and sounds like crap from the 2100-2600 rpm range. It vibrates a lot, has a noticeable decrease in power, and the exhaust sounds like a import fart can. Right before that range, at 2000rpm, the car falls on it's face if you try to accelerate. It feels like its being flooded, almost like turbo lag. Before and after that rpm range, it runs and sounds like a champ.

Recent/relevant history:

I have recently had it parking lot tuned to delete codes for long tube headers. They deleted: EGR, AIR, Rear o2 sensors, and skip shift. When I took it to get tuned, the tech told me that I had both knock sensor codes up. I told them that I was aware and the sensors and harness were on order. They said okay, and proceeded to delete the appropriate codes. A week later, I install knock sensors and harness. During that week of driving it around, the codes never came back on, which I found strange. I install knock sensors, put everything back together, crank it up. It's knocking like crazy, so I let it run for a little bit assuming the knock sensors would figure out what was going on and fix it. They did after a few minutes and the knock completely went away. Shortly after all of this, I installed the long tubes with a y pipe and a single in, dual out muffler in the stock location. All 3 inch pipe.

I think this problem has been around for a while. The falling on its face at 2k rpm and vibration has always been there, but it was not this bad. I attributed the poor performance to the bad knock sensors and the vibration has always been a mystery that I have been trying to figure out for the better part of a year. I never noticed how awful the exhaust sounded until I put the long tubes and new exhaust on it.

So what's going on? Did the tech delete my knock sensor codes instead of resetting them? Would that negate their ability to work, or just a code coming up that they are not working properly?

Thank you in advance, sorry for such a long post.

Chris

 

Impossible to do over the internet.

 

I tuned a 2000 ws6 that had the exact same problem you are describing. The MAF was bad. I mean exact same problem.

 

With EGR delete, did you / they eliminate the excess
spark advance (either killing the EGR option, or by
zeroing the EGR specific advance and using a more
sane spark map from a non-EGR car)? The VE table
can also be a mess, EGR bends that when active
and it no longer is.

 

I have no idea if they eliminated the excess spark advance or not. I know nothing about tuning. I will definitely call them and ask them though. I've pretty much just decided that I need to take the car back to them and see what they say. Thank you.

Chris

 

So would that be a MAF and a tune, or would just replacing the MAF fix it? I could see it being a MAF because it does other random intermittent things like drop the idle real low sometimes and it dies when I crank it every so often.

How did you trouble shoot the MAF? Is there anyway to do that without having it hooked up to HPTuners?

Chris

 

Unplug the maf and see if the car runs the same. If so, it is likely your problem. The owner of the car I tuned didn't want to spend the money to fix the maf so I just did a speed density tune on it. Better in my opinion anyway.