BassProCamaro97

I have about 300 miles on the car since the tune up and header job and it seems like the car is running way to rich.

By way to rich I mean when I lay on it, and if you are behind me, it almost brings you to tears. The gas mileage is down a few MPG, in the tune of 190-200 miles per tank.

What do you think whould cause this. There are no codes up, and the car is strong from idle through the powerband. the only things i can think that may be wrong are the 02's or the PCM. I'm going to send the PCM out to madZ28 to see if it helps matters any but thought it would be a good idea to ask you guys if you had any idea what might be causing this.

Also where can i get a good scanner that will read codes and the functions of sensors and other important things of that sort, and how much should I be expecting to pay. Sorry bout the long post and i appreciate any help you guys can give me.
~Jim~

Injuneer

Common causes of running rich are exhaust leaks before the pre-cat O2 sensors, and misfires. Both of those problems are very common with header installs. Are your headers cera-metallic coated (e.g. - JetHot or similar)? There is some speculation that the initial burnoff from coated headers contaminates the O2 sensors.

Any OBD-II scan tool (not just a "code reader") will be able to access the PCM codes, sensors and parameters. A tool that supports "GM enhanced" parameter scanning will give the best results. You can also use something like AutoTap on a laptop. There are several good OBD-II software setups available.

BassProCamaro97

Yes the headers are coated, i let it run about 20 minutes with out the o2 for that reason, do you think that could still have happened?

I do not have rear 02 sensors, so their not reading any airflow.

Where can i get the scan programs or scanners themselves?

thanks fot the reply
~Jim~

Injuneer

This is the link for AutoTap, and a couple others:

http://www.autotap.com/products.asp

http://www.auterraweb.com/

http://www.palmerperformance.com/

http://www.obd2.com/

http://www.obd-2.com/

I'm sure there a many more... but I stopped using the factory PCM in 1999/2000 so I've lost track of some of the newer products.

BassProCamaro97

Has this ever happened to anyone else before? I haven't got around to checking for a vaccum leak and I am sure I do not have an exhaust leak. The car runs rich from start up till you close it down and the idle feels a little rough but the RPM's dont jump or anything like that. I do not have a SES light on but is there possible that there could be something wrong that would cause this and not turn up on the dash?

Injuneer I appreciate all the help, it has been very useful

like I said the onlt thing that has me scratching my head is that the car runs very strong other then the backfires.

Thanks
~Jim~

blk97ta

i've been having problems as well i've got a 383 with a procharger and when i run it with the maf hooked up the car .the car gets pig rich like a crop duster ! if i run the car without it idles good and doesn't smoke if i hook it up while it's running and the car stalls out ! BAD MAF ???

BassProCamaro97

well i do have another MAF so I'll swap that in and see if there are any changes tomorrow, but some how i do not think this is what is causing my problems.

I've talked with a few folks who are very knowledgable about cars ( more then myself) and they are leaning towards 02's or the flash i had put on the PCM, granted i have a feeling the guys who did my PCM messed it up but I cant say thats it for sure.

Thanks for the reply
~jim~

Injuneer

Put a scanner on it and check for codes. I've seen cars with the SES bulb burned out, or removed to it won't show up. There are some codes that don't turn on the light.

BassProCamaro97

I decided to bite the bullet and just pick up an autotap for the laptop. So im going to check it all out when i get the chance.

Any certain parameters that you think maybe causing these conditions (richness and bad idle) that i should check out. Assuming that no codes show up of course.

thanks again
~Jim~

BassProCamaro97

So heres the newest update. I lifted the car and torqued all the header bolts down nice and tight to eliminate any chances of exhaust leak. Next given many poples opinions i decided to replace the O2 sensors. nplugged the Battery for about 10 minutes and then drove the car home. The car was exactly the same. Not a single change in idle, exhaust pop or the smell of fuel from the pipes.

It also seems that when i try to nail it from a stop it feels pretty weak but then gets rollin, almost like it hesitates just a bit. I've read plenty about this and it seems like I've got the same problem.

So given the new details can anyone give me any advice from here?

Thanks you guys have been a big help so far!
~jim~

BassProCamaro97

Ok guys I finally hooked it up to the autotap and checked all of the fuel system that I could. The car did not come up with any misfires. The long term fuel cells were. Bank 1 stayed very close to 23% while bank 2 went from 12 to 20% avg 15%. Short term was; Bank 1 -10.9 to 6.3 while bank 2 went -12.5 to 2.1. The ignition timing advance was roughly around 20 deg and increased as the RPM's increase. The idle was dancing any where from 750 to 900.

Does any of this sound weird to anyone, anyone have an idea what is causing the rough idle and richness? Injuneer?

Also is there a list or something where I can get what all the normals should be for all the paramaters.

Thanks alot I hope you guys can help me through this
~Jim~

BassProCamaro97

Anybody have an idea?

Injuneer

If its truely running rich, the long terms are pouring in fuel the engine obvioulsy doesn't need. If you think about it, adding 23% extra fuel richens your A/F ratio from 14.7:1 in closed loop to 11.9:1. You need to find out why. What is the source for the "false lean"?

You seem to have ruled out exhaust leaks (simply tightening the bolts won't necessarilly "fix" a leaking gasket). Your saying that AutoTap hasn't found any misfires. That rules out the two most common causes. You have new O2sensors, so they should be OK. Have you checked the wiring for the O2 sensors? With the LT's, I'm assuming you have extensions. Are the good quality?

Vacuum leaks can cause the long term corrections to elevate, as will an MAF sensor that is under-reporting air flow. But in those cases, the long terms are correcting a "true" lean, and should help keep the A/F ratio where it belongs. Something is fooling your PCM into thinking its running lean.

For info on what some of the scanner readings mean:

http://members.aol.com/InjuneerZZ/ScanMast.htm

BassProCamaro97

Injuneer, thank you so much for the reply. I can't tell you how much you have helped me.

I am in fact running extensions. They are good quality im not worried about that. One of the O2 harnesses i did have to cut and extend because it would burn on the headers no matter how i would have routed the extension. I did do all the correct steps to properly extend that harness so I'm not worried about it sending false reading due to that.

The things I am worried my be causing this are possibly a bad PCM tune? or possibly false knock from the headers. When im next to the car I can hear what sounds to be noises commming from the passenger side but I dont see anything or feel anything that would constitute an exhaust leak although I may be wrong.

from your personal expirence do you think there could be an exhaust leak doing this? And if so how would I go about finding it? I can not see any places that show black marks nor feel any spots that are blowing hot air. So I'm really at a loss for what could be doing this to the fuel system.

Do you recommend any certain parameters to check in order to hunt this dang thing down?

Again I'm so thankful for your help.
~Jim~

97 LT4

This is great guys, this is almost identical to my problem with exception to the backfire. Car idle s a little rough and is rich to the smell but under WOT seems to run well. Sorry just getting a little excited about a possible solution. Oh and my car shows no misfires as well.

Thanks