What would cause my LT1 to run rich? - Third Generation F-Body Message Boards

jagevileye21 · 05-29-2009, 02:58 PM

Yesterday, I took the car out for a drive and it barely wanted to accelerate and it seemed as if it was going to shut off. I smelled exhaust fumes and seen the car puffing black smoke. I have a bad exhaust leak on the passenger side. So I pulled the header and checked my plugs. All the plugs on the passenger were covered with carbon. I couldn't even clean them. Next, I replaced the header gasket and put some of my old NGK plugs in. After starting, the car cut off three times while putting it in reverse. I finally got it too stay cranked by pulling the connection to my MAF(had engine diagnostics done a while back shop said it was throwing codes) which made the black smoke go away. The car cranks and idles fine. Just under a load it lopes and shakes.

Vacuum: 22 psi (steady)
Fuel Pressure: 40 psi

If my car requires 93 Octane and 87 Octane is used. Would that cause any of these symptons?

Today, I drove the car to work the initial take off was harsh. So, I stopped the gas station and put 93' Octane in the car. The car did not hesitate or anything the rest of the way to work. However, I still don't think my problem is fixed.

Any ideas???

Thanks,
Jay

drperformance · 06-01-2009, 12:46 PM

I would start by checking to make sure no air is getting into the engine other then trough the TB. Any unmetered air will cause the o2 sensors to make the car go rich.

-exaust leak before the o2s
-vacuum leak
-leak in intake after the mass air/throttle body
-bad o2 sensors

And yes, if you have a rich tune with more timming then it would run like crap on 87.

jagevileye21 · 06-02-2009, 02:18 PM

Thanks for the information. I don't have a vacuum leak, but I'm pretty sure there is an exhaust leak before the o2 sensor. My o2 sensors are only about 1 & 1/2 years old. I willl try to take care of the exhaust leak and get the car scanned to see if that changes anything.

Jay