LT4 running rich- possible causes?
Thread Starter
Instructor
Joined: Oct 2012
Posts: 189
Likes: 36
From: Austin, TX
LT4 running rich- possible causes?
Hey all, I have a line on a 96 GS that the owner says "runs rich" and after a local Vette shop worked on it, it ran good for a bit and is back to having issues. I am not as familiar with the LT4 as my car has the L98, so wanted to ask if anyone could offer an opinion on what could be causing this issue. I assume its not a clogged air filter, lol. Car has 39k miles on it. Thanks for any ideas.
Burning Brakes
Joined: Aug 2023
Posts: 1,093
Likes: 35
From: San Diego
One thing that will make it run rich is a busted catalytic converter. Listen and see if either is rattling. Doesnt take much to cause on and off richness.
And if this started after work on it, what work was done to it?
And if this started after work on it, what work was done to it?
Pro
Joined: Sep 2000
Posts: 524
Likes: 57
From: Chicago ish
Mine was running fat when I got it. Vacuum leaks. Rubber gets old and loses its seal and there’s a lot of little connections without anything to hold them tight. Also the throttle body could have one of those rubber diaphragm looking gaskets under the cover, which balloon and leak. There’s a million little places for vacuum leaks to mess with it. I thought I had an intake leak but that wasn’t it. Check everything from the MAF back. Especially the PCV valve grommet and elbow. Mine was leaking from the valve cover vent pipe connection at the throttle body. And leaking oil from the PCV valve nipple under the throttle body. Once you know you have tight vacuum connections everywhere, then see where you go from there. Maybe clean the MAF too.
