Texhotrod593

iTrader: (7)

I am very new to this site. I might need some help thru it. Thats not my problem though. I have owned a 99 ss for 3 years and have added just a few things to it. Gran. MAF, Gig. Cold air, Moly pushrods, pacesetter long tube headers, off road y-pipe(no cats), flowmaster etc... now the headers is where i found my tru problem. this car has ran great till i put them bad boys on. i do not have a tune on it and i have had the ses light on for some time for the back O2 sensors. This car right now is running richer than any car i have ever encountered. i pulled the new plugs i just put in when i put the headers on and they were pitch black! black soot all over my driveway or being burst in the air while im driving! idles rough, and jumpps and jerks around while driving. since then it threw a MAF code so i replaced it with a new one along with a new TPS, and ATS. This hasnt changed one bit even after clearing those old codes! I even tried unplugging the MAF and letting the car run in "home" from the map sensor and TPS and it still runs the same. Please someone that might can give me ideas!!!. I am very close to giving up and trashing this car because of it and its my baby. help

Billf6531

First, do you have an exhaust leak that would allow air in before the front O2 sensors? If so, fix it. Second, tune it properly by setting your PE table to some sane value(s) and use a wideband to correct the VE table so that actual=commanded. Then tune the MAF table.

If you fail to use good tools (proper diagnosis, wideband, tuning software) and methods, you'll continue to get what you're getting - which by your description is garbage.

Good luck.

thunderdan74

iTrader: (1)

check all the pliugs. Did you crack one? Are there any that are not black? If so those 'clean' ones are not firing. Replace them.

Frost

iTrader: (45)

Wait..... codes on both back O2s? Maybe you melted those factory cats with all of those mods on a factory tune. I hear the G-MAF may actually skew you a bit lean "for HP" and such... The lack of airflow resulting could make the car act fat...

2xLS1

iTrader: (25)

Don't assume the SES is only from the rear O2s. Get the codes read and see what other codes are set. If it's running that bad, you probably have other codes too. Check youe Eng Sens fuse in the under hood fuse box.

ringram

Long tubes can mean the rear sensors are too cold to switch properly. Best thing is to disable the rear o2's anyway. As mentioned checked for leaks, they will cause extra fuel to be dumped in. Does it run ok when cold (ie open loop) If so its your closed loop system that is messed up.

eallanboggs

iTrader: (1)

Don't blame the headers for this problem. The only place he could have a leak on that header is at the flange to the head. You did use a good exhaust manifold gasket and Stage8 header bolts, right? Well then we know that's not his problem. With the OR Y pipe there are no cats so the rear O2s don't exist. He might get a DTC from the rear 02s unless he deletes them. He needs to look elsewhere for this rich condition.

Texhotrod593

iTrader: (7)

Yeah thanx guys!.. Havent found the excact prob yet but last night i did drive it a little more with the window down and i think i could hear a little exhaust leak on the driver side. Now as for good gaskets and etc i used the copper press type that came with the headers along with splicing in longer wires for the front O2's. but it seams to me if it had a leak at the head/header flange, dont you think it would just leak and not suck in air? By the way....it does run alot better right after start up but it will spit and fire and pop till it runs warmer thus running worse. and i did check all codes. there were more than just O2 codes. I willl just go read them again and post them. thanx guys! you all have giving me a little extra wind to keep going!!

SSpdDmon

iTrader: (10)

Sounds like the front O2's need to be replaced after all exhaust leaks are sealed up. I'm willing to bet the PCM's not reading them correctly after you spliced in the extensions. Buy some Vette O2s or some replacedment O2s with extensions and have someone reset your fuel trims.

edcmat-l1

iTrader: (10)

I have seen open and grounded DOWNSTREAM 02s cause excessive fueling. Even against conventional thinking that the fronts (only) control fuel.
Esp in applications just like this where they have been eliminated but not turned off. Get them turned off or install sims and the problem will probably go away.

2xLS1

iTrader: (25)

Throw those away now and get new O2 sensors and real extensions or the Vette rear O2s with the longer leads.

2xLS1

iTrader: (25)

I've only seen that on OBD2 Gen1 Vortec trucks. Never on Gen3 vehicles.

edcmat-l1

iTrader: (10)

I've seen it on a couple LS camaros. And the older stuff. Hell I've even seen a Ford Aerostar do about the same thing from a faulty downstream 02.
One of the Camaros that I saw do this, ran so rich the fuel was coming out the pipes RAW. It was like stream, white smoke but it was fuel.
I think some of them, and I dont know why some but not others, over fuel to see if they can get the downstream 02s to move.
On the Aerostar, the fuel trims would go to 25% and sit there, til the cats started stinkin.

DrkPhx

iTrader: (15)

I would switch the GMS MAF for a stock unit. I can't say for certain if it's the problem, but at least eliminate it from the equation.

ACG

iTrader: (1)

I've had this problem happened to me. After installing headers it ran rich, it had o2 sensors codes and maf codes. I replaced the front o2 sensors, switched maf sensor and nothing changed. The fix was a popped fuse for the engine control or engine sensor 15 or 20 amp fuse.

Texhotrod593

iTrader: (7)

ok guys. I am lovin this site! you all have very comforting ideas about this. I have turned the car over to a buddy the works in a well known shop with scanners and such to find the problem. I do have to say...on the last comment. that sounds very close to what i started thinking the problem was. I didnt even think about checking any fuses. i will call my buddy tomorow and let him know that idea also so mayabe it will be a short diagnostic for him. Again...Thanks to all of you guys. i am most defenently going to visit this site more often!

playtoy_18

You've probrably got two problem's
The GMaf is just a MAF with a bigger housing and a resistor to trick the voltage to the ECM so it will run leaner,trash it and run the stocker.
if the rear o2's are still plugged in without cat's then your ECM is also running in Cat overtemp protection mode more than likely.

1320FEVER

iTrader: (9)

Isn't retuning the PCM a must after installing headers? If the PCM is not retuned than it will most definitely run way too rich. Exhaust leaks will cause this also. You could have both problems.

1320FEVER

iTrader: (9)

I agree with this statement also..

SSpdDmon

iTrader: (10)

Not a must....just recommended. My friends both ran headers for years without issues. It'll most likely appear to run leaner down low (in theory because of the cooler O2's) causing the fuel trims will compensate. Then, those added trims are added to WOT. They will most likely offset the better breathing, naturally leaning effect of the headers and keep you in the factory AFR range (high 11's). Some have more side effects than others when it comes to NBO2 issues. But like I said, my friends and I never had an issue. It's almost a crap shoot anymore....you know...sometimes you get the bear...and sometimes the bear gets you.