I just got a dynomax cat-back put on thursday, and the tips are already sooty and blackened. I've also noticed black exhaust clouds at high rpm. I thought it may be related to the new exhaust, but after about 300 miles, it seems unlikely. I believe (?) this indicates the car is running rich. I know that means there is too much fuel in the air-fuel mixture. And there my knowledge ends. How does one correct this problem? If I have to replace something, I'd like to upgrade (i .e. not replace with OEM part). Is this a common problem on my year car? The car is a 1994 Z28, totally stock (except obviously for the new exhaust).

I'm a car idiot, but I'm here to learn.

 

hmm, sounds like an ignition issue to me...

air fuel spark, its obviously not a lack of fuel, i doubt its air and that leaves spark

 

so if it is an ignition problem, i would be wise to upgrade to MSD, etc etc ignition module? Could it be as simple as new plugs?

 

When was the last time you gave it a tune up? Dirty air filter will also cause a rich condition, carbonizing in the intake (SeaFoam cleaner), lazy O2 Sensors, etc...

 

How does it run?The first thing I'd check if its stock and assuming filters and plugs are ok is the vacuum line to the regulator.

 

Yep, need more info.... what's the latest? Did you give it a tune up? After you go through the general maintenance, you might want to get a www.pcmforless.com program for your car. There is so much to do or that can be done to our rides... This is where the fun begins. As you replace things, you can replace them stock or upgrade.

 

Leaking valve seals? Burning oil?

 

Well, I checked the air filter, and it's fine. I don't have any leaking oil or anything. Also, an important piece of info I left out before is that the car is right at 90000 miles. This would be time for a tune-up, yes? How difficult would it be to do a tune-up myself? I would plugs, wires, and what else. I'm going to get a shop manual for the car today, maybe I can answer some of these questions my self. I'll be sure and post the results in a few days. Thanks to everybody for their help and patience.

 

Do you have headers? That would be a factor in how long it will take you for a tune up. Yes, get plugs, wires, and Seafoam to use in the fuel and oil. Plugs and wires should take about 2-3 hours to remove and replace... do one wire at a time. Seafoam cleaner is a snap... takes about 15 minutes.

 

No headers, everything under the hood is just as GM made it. I seem to recall that one of the plugs (#7 maybe) was supposed to be a pain to switch out, I assume b/c the rear of the LT1 is way the hell up under the dash. My buddy has a 87 T/A GTA with a L98, and he said his mechanic made some custom tool to get to his hard-to-get plugs by taking the front tires off. Is there some special thing I need to know when changing them? Also, I've seen several different brands of wires and plugs and whatnot. Can you recommend any particular one, or is one just as good as another. Thanks again.

 

It makes it easier to raise the car on safety stand and have a buddy around. I find it easier to change the wires from under the car. The #7 has a bracket that holds it to the block. The #6 & #8 are held by another bracket to the block. You can use any wire but I'd like to keep the wires matching the control boxes (MSD wires for MSD ignition boxes, Jacobs for Jacobs, etc.). For your engine Taylor wires would be just fine. Summit Racing has them for less than $50. It helps to have a buddy or you'll be getting over and under your car frequently. Good luck.b