Need Help Please--1999 Z28
Need Help Please--1999 Z28 
My car is a 1999 z28, 107,000miles automatic, lid, pacesetter longtubes, ory,air!, egr! slp loudmouthwhen the car was stock, no cats , the car ran 8.40s down to the paper filter
first mod I added was the slp loudmouth, and removed the flowmaster muffler.
took it to the track, and car an 8.52 @84 mph -----then I added a k&n airfilter, airlid, longtubes, ory, msd 8.5 wires, ngk tr6 spark plugs and the car seems to have no low end at all, burns the tires, but not the same from stock even, seems slower now. still ran a 8.51 @ 85 mph at best with this setup??? so basically it wastes alot of gas, maybe 180 or less miles per full tank (super unleaded).
well took the car to track today, and was very good air here in texas, and ran even slower now, ran an 8.80 @ 82mph, so lost more tenths, and mph!!
im thinking its running rich, and I may need a tune but not sure if the problem is really a tune needed or if its something else like the slp loudmouth making me lose backpressure, or some other technical thing, but any help or input would greatly be appreciated, this is so frustrating as we all know!
just scanned it, and i have the p0332 , p0140, p0160, and p0405 codes stored. so sorry to ask but can the knock sensor really make my car do what is stated above>?
TECH Fanatic
Joined: Feb 2004
Posts: 1,259
Likes: 0
From: Lexington, KY
If you are getting knock retard, yes.
With your current setup it is most likely rich though, and definately in need of some tuning. IMO headers require a tune or they can actualy be harmful to your car.
With your current setup it is most likely rich though, and definately in need of some tuning. IMO headers require a tune or they can actualy be harmful to your car.
Staging Lane
Joined: Aug 2006
Posts: 68
Likes: 0
From: Powell, TN
Sounds to me like you are lean. Everything you have done has allowed tons more air into the engine. Most cars run rich from the factory, that's why mods seem to help, up to a point, but then you overcome the factory rich condition and the more mods you do, the leaner it gets and the worse it runs. This lean condition would also account for any extra KR you may be getting.
This is also the reason you lost your responsiveness. Your fuel trims are probably way out of wack. The worse your fueling gets, the more the O2s have to hunt to get the fueling back to stoich (14.7 AFR). The more they have to hunt for the correct fueling, the slower your throttle response will be. Definitely get a tune, you've probably got 25 or more horsepower to gain.
The 140, 160 codes are for the rear O2s, a tune will take care of this too.
This is also the reason you lost your responsiveness. Your fuel trims are probably way out of wack. The worse your fueling gets, the more the O2s have to hunt to get the fueling back to stoich (14.7 AFR). The more they have to hunt for the correct fueling, the slower your throttle response will be. Definitely get a tune, you've probably got 25 or more horsepower to gain.
The 140, 160 codes are for the rear O2s, a tune will take care of this too.
