96capricemgr

It is getting richer at the top based on what you are reporting so it looks like just bad tuning at this point. You have grossly oversized injectors and what should be a good choice for a fuel pump.

Wouldn't hurt to be prepared to monitor fuel pressure on the dyno but I really don't think it is a problem.

The MAF is stock right? As in you haven't screwed it up with a grinder or anything. That sort of thing makes mailorder tuning a nightmare.

ascastil

MAF is stock. I was under the impression that the 42# injectors would be taken into consideration in the tune?

96capricemgr

Yes they should be tuned for but they are still much larger than necessary. 30lbs would have worked, 36lbs would have been fine even by the standards of those who are overly conservative and suggest keeping the DC low.

It is tuneable, you have them so run them but you should not have bought injectors so big.

ACE1252

What are the specs on your exhaust? If headers, Jet Hot coated or not?

What brand of injectors did you buy? Are they new or used?

How old are your O2 sensors?

As many have mentioned, need to data log it and see what is going on.

Guest47904

I would fire it up and check the fuel pressure at idle. Your Walbro pump is not on my favorite list. If it' appears to be ok, pull the vac line and plug it to see if the pressure then rises.

If you go back to the dyno, try to keep the fuel ratio at or below 14:1 by restricting the fuel return line. If you keep consistently higher fuel pressure and have the same lean results, you may want to double check with the programmer what numbers he used.

96capricemgr

Far as the intank fuel pumps for performance application that easily fit the LT1 tank it is chinese junk or Walbro. Far as I know all the replacement 255lph pumps we have for these are one of those no matter what box they came in.

A lot of us have had good results with Walbro from Racetronix.

ascastil

Pump and injectors are both from racetronix. Injectors are flow matched. True dual 2.5 inch exhaust, no cats, o2 delete. Pacesetter long tubes, no jet hot.

96capricemgr

uncoated headers could easily cause melted wires and such.
By O2 delete you mean just the rear right?

Some guys will say the 2.5" duals are a problem and maybe it isn't ideal but it isn't that big a restriction unless the setup is rather aggressive and the LSA really tight like below 108

ACE1252

I was mainly looking to see if maybe his O2's were contaminated by the Jet hot coating. They have been known to kill O2 sensors.

At what point in the exhaust was the AFR bung welded?
How old are the O2 sensors and what brand are they?

ascastil

I think the bung was put near the x. The o2s I believe were put in when I first rebuilt the bottom end, approx. 15k miles ago. Again, I can't be positive, its been a few years. The car isn't driving much, lol. I'm unsure of the brand. Just the rear o2s were deleted.

96capricemgr

I guess it should be said Bosch narrowband sensors do NOT play well with the LT1, someone posted a technical explanation within the last few months but it has been well documented for a lot of years.

ascastil

Possible bad news, but making progress. Checked fuel pressure tonight and looks like this:
KOEO-41psi, SLOWLY, and it holds it with the key off.
Idle-41psi.
FPR vacuum line removed-46psi.
It doesnt climb to 41 psi when I first turn the key, it takes 15-20 seconds. I was gonna do the test back to back to verify readings, and it read 35psi, and took forever to get to 40. But when I turn the key off it holds the pressure everytime. Also, when I first turn the key and it sounds like its priming, the pressure rises quick, drops off, and makes its way back up.

Injuneer

When you turn the key to "run" the fuel pump should prime for 2 seconds and shut down. At that time it should have reached 40psi. Are you saying yours continues to run for more than 2 seconds, and that the pressure rises slowly, drops and then rises again?

When is the last time the fuel filter was changed?

ascastil

Just did the test with the key on again, and this time it rose to 41 pretty quick, and when I turned the key off it holds pressure. Im just worried about the other few times when it didnt rise as quick. Sound normal or no?

ascastil

The fuel filter hasnt been changed recently, but there isnt a lot of miles on it.
It primes for a few seconds up to about 44psi. After its done priming it drops down to 36, and is now quickly reaching and holding 41.