NightwalkerLS1

iTrader: (2)

I recently had new pacesetter long tube headers, borla cat back exhaust, and 4.10 gears installed on my otherwise stock 2000 trans am ls1. Other new parts on the car also include new AC delco fuel filter, NGK spark plugs, MSD plug wires, O2 sensors with extensions and TPS sensor. My tuner said he was having issues with the car going lean at WOT while attempting to tune the car, wideband O2 sensor is jumping up around 16 at WOT. Otherwise the car runs fine, just can't get on it until the retune. He has suggested that I may have a faulty MAF (my K&N has now been replaced with a wix paper filter) causing the issue and has suggested I go to an 85mm MAF anyway which will also make for a better tune, sounds reasonable to me.

Keep in mind I cannot get the car retuned until I finish breaking in the 4.10 gears that were installed immediately following the tune, so in the mean time I am trying to make sure I cover all possible scenarios as to why this is happening before I take it back to get the tune worked out.

The car was also having issues holding idle on start up occasionally which I traced to the IAC valve after the initial tune was done, and occasionally this would occur even before the tune was done. I was curious if this faulty part could have affected the tune? I figured out the IAC motor was toast, so I replaced it and that issue was resolved, noticeable difference.

At this point I figured I should check my fuel pump/fpr. Here is what I came up with, on turn of key I am at 52 psi and holding. On start up and at idle I hold a steady 58 psi. On pushing the peddle in slowly and raising to high rpms I continue to hold steady at 58 psi. If I pound the gas peddle the psi drops 5 to 7 psi than jumps back up quickly. Sounds to me like it should not be dropping that much so I am going to replace and upgrade the fp/fpr just to cover my ***.

I have purchased a new 85mm truck maf with harness, I have also ordered a new racetronix pump from texas speed and a delphi fuel pressure regulator from rockauto. I am looking for suggestions on any other issues I should look into that could be causing this.

It should also be mentioned that Josh at Spartan LSX performance did all the work along with the tune. Anyone who knows Damian from these forums knows that the guy is awesome and really knows his ****.

dreww

iTrader: (1)

Im assuming your tuner has played with the PE sections of your tune file? if he cant get it to stop going lean with the tune, then there is likely mechanical issue. I would lean (excuse the pun) towards fuel pressure issues. A fuel pump generally shows reduced pressure when its failing and the first sign is weak pressure at WOT/redline.

NightwalkerLS1

iTrader: (2)

After doing some more testing I think my pump is weak.

Slowhawk

iTrader: (12)

More than likely it is just the MAF as he said. You can easily tell looking at the frequenzy at WOT. It will read lower which dumps less fuel.
Easy fix. new MAF

NightwalkerLS1

iTrader: (2)

Thanks for the reply. At this point this made for a good excuse to upgrade my fuel pump anyway so it should all work out.

Becker

iTrader: (4)

Slowhawk - what range is normal when logging MAF data for an LS2.

-Hz at idle, cruise, wot?
-G/S at idle, cruise, wot?

Id like to rule out a bad MAF for myself on a slightly similar issue, sorry to thread jack. Keep us posted I am interested in the overall fix.

InfrareV

Idle - 3000Hz
Cruise - 4000Hz
WOT - 7000Hz +

That's how mine shakes out, I imagine most cars run something in that ballpark. Although I don't think it's critical. As long as it it moves in proportion with engine speed and load you'll be able to map the g\sec appropriately and calibrate the MAF.

redbird555

iTrader: (14)

I'm not to sure about the maf as im not a tuner lol but the fuel pressure shouldnt drop. It should hold steady at 58psi all the time.... Also you seem like your testing it with the car in park or neutral, log it under load and it will most likely drop even more. Time for a racetronix pump.

NightwalkerLS1

iTrader: (2)

Just as a follow up replacing my fuel pump and maf cured the issue. I suspect it may have been a combination of the two.

Slowhawk

iTrader: (12)

They all drop. It's the cheesy design of the fuel system.