Need help, car seems to be running rich

**3tas4me** · 09-03-2024, 06:29 PM

The car is a 2001 Firehawk with only 7157 miles on it. I bought it two years ago out east and drove it home. It had 4200 miles when I left the sellers home.

On the trip, the best I could do for fuel economy was 25 mpg. My other LS1 routinely gets 30 mpg. Both are 6-speed cars. I also have noticed that the exhaust has an odor. It smells all the time, at cold start up and fully warmed up. I pulled the injectors because I figured with the low mileage and sitting so long, they might be sticking. I had also done a fuel pressure leakdown test and it lost pressure very quickly. I installed the injectors on Sunday and have drove the car. It starts better and runs a little better, but the odor and poor mileage are still there. Clearly the injectors were not the problem even though when they were tested, all were dirty and three were more so than the rest. I have used my Genysis scanner and everything seems ok other than the LTFT seems to go negative, which means the computer is pulling fuel. The car is running rich and I am not sure what is wrong. Engine is stock, no mods.

***SMWS6TA*** · 09-04-2024, 03:42 AM

It doesn't sound like your getting any codes but with your scanner I'd check the pre-cat o2 sensors. Seeing if they are going into close loop. even then should throw a code if not.

I wish I had even 20 mpg. But with Hp comes with less mpg.....

**3tas4me** · 09-04-2024, 05:51 AM

I did. I am in closed loop. IAT temp seems normal as does the coolant sensor. O2 pre-cat seem to jump around like they should but the right bank post Cat sensor seems a little lazy. There just isn't anything on the data stream that really jumps out at me.

**3tas4me** · 09-04-2024, 08:14 AM

I just rechecked my fuel pressure again. Turning the key on with the engine off, the pressure goes to 50 psi and then leaks down quickly. Bad regulator I would assume. Would that cause a rich condition?

***SMWS6TA*** · 09-08-2024, 05:49 PM

Originally Posted by 3tas4me

I just rechecked my fuel pressure again. Turning the key on with the engine off, the pressure goes to 50 psi and then leaks down quickly. Bad regulator I would assume. Would that cause a rich condition?

No if anything it will cause a lean condition.

You should be seeing 58 psi at the rail for fuel pressure.

I"m willing to bet the O2's are done and need replaced. Especially if they're OEM or 5+ yrs old After a min or two it should go to open loop once the engine has reached op temperature.

**3tas4me** · 09-13-2024, 05:06 AM

Update: I took the car to a shop because I was expecting to have the fuel tank removed. They found that the computer was recording misfires on every cylinder at random. They were unable to diagnose it further as they said it would require additional time checking wiring etc. I have not felt or heard and misfires while driving. When picking the car up from the shop, the owner called another shop and they suggested doing a relearn procedure on the crank position sensor. Since I have a Genisys EVO, I figured I could do that myself. Brought the car home and was unable to do the procedure with my scanner. I took the car to the local Chevy dealer where they did the relearn procedure. They told me to drive it as it may take a bit to get the extra fuel out of the exhaust. The odor does seem to be less, though it is not gone. I will be able to verify if this helped on my next fill up when I will be able to determine if fuel mileage is better.