Big Al

iTrader: (1)

My "new to me" 95 Z28 is way rich. Has a lot of aftermarket stuff and a custom tune. It was tuned for nitrous and is fat as hell without it. Trying to find a way to lean it out without a lot of work or in my case learning how to program the PCM and buying software and so on. It's fat everywhere from eye burning idle to the red line. Think they were trying to keep it fat for the nitrous.

So I'm wondering if I reduce the fuel pressure what will happen or is there another way? There is a fuel pressure gauge at the rear of the intake, and an adjustable regulator. The gauge says I have about 47 pounds pressure, engine off. Goes down to around 40 with high manifold vacuum. No idea how accurate it is or any reason to believe it's not.

BTW, it has long tube headers and the O2 sensors are not warm enough to work and most likely are "tuned" out anyway. Has all the normal bolt on mods, large throttle, mild cam, MSD ignition, 42 lb injectors and so on.

Al 95 Z28, TH400, S-60 w/4.30's 28" Hoosiers.

CRAZZ28

iTrader: (13)

what a/f readings are you getting? I doubt the O2 sensors are tuned out unless it was a track only car.

RamAir95TA

iTrader: (2)

Changing the fuel pressure will only yield temporary results. There's no way to safely and accurately change your air/fuel ratio without a wideband, datalogging, and tuning software.

gregrob

iTrader: (8)

Spray it

Big Al

iTrader: (1)

Since the O2 sensors are cold they are saying the engine is lean. They are black as coal. Checked the power to the heaters and it's there, removed one O2 sensor and tested it, it's fine. Heater works and the O2 readings are there.

I'd be willing to bet they are tuned out or at least should be. The O2 sensors are AC AFS75.

Al

CRAZZ28

iTrader: (13)

Or since they are junk they are making the motor dump fuel. what you need to do is get a scanner on it and see what your fuel trims are. that will tell you what the O2's are telling the pcm. Or try some known good sensors. I doubt its in the tune unless the injectors were incorrectly accounted for, because there is no reason to change commanded a/f ratio anywhere except WOT for nitrous.
I was originally asking for wideband numbers.

Big Al

iTrader: (1)

Man do I owe you guy's. Crazz28 got me checking things. Since I removed the O2 sensors to check them, what about something in the wire loom? Like an AF gauge mounted on the windshield pod. Did some checking and found the problem. Even got the gauge working.

So I ran it in the garage a while, here is what I'm seeing:

Integrator R 124 L 129 < these numbers jump around a lot, but this is what I'm seeing at idle.

BLM cell 16, contents 133. If I raise the RPM and let off it changes to cell 18 and right back.

If I hold the RPM up the integrator numbers change. And for the first time since I've owned it, it went into closed loop. I'm thinking all it needs now is some time to "learn."

If I'm wrong, please tell me.

Again, many thanks for showing me the way,

Al 95 Z28.

LSWHO

iTrader: (1)

The idle BLMs have no effect on wot. And those values are pretty good as they are.

Heres a question, is this a wet kit or dry kit? If it's a wet kit just change your fuel jet. Why hasn't somebody already said/asked this?!

Since you have an obd1 car tuning is free. Just download tunerpro...

Big Al

iTrader: (1)

Downloaded it. Trying to learn how to use it.

The car has Nitrous but I'm not using it. Bought the car recently sans rear axle and torque arm. It had a 12 bolt, I put a S-60 in it. I'm fighting all kinds of things, had a bad miss, found three bad plug wires. 2, 4 and 5. Then got into the DTC 42 thing, now the AF ratio. I'll get there. I'm reading everything I can find on the PCM and trying to learn how to tune it. I'm so not up on this car, I spent about two hours trying to figure out the OBD I with OBD II connector. Went around in lots of circles before I figured out everything I was reading was wrong. Got Freescan running and at least can scan it now.

Last Friday I took it to the strip, ran 12.77 @ 106 busting up all the way down. I'm about ready for another try.

Al 95 Z28, TH400, S-60