Alright so Ive been boosting for about a week now, about 6 psi. Its been great, i love it. I have some small leaks which im working on, seeing full boost at like 4 cause of exhaust I think. My friends tell me they see black smoke when in boost when behind me which i assumed was me running very rich with a 12:1 fmu. The crap blink a/f showed this and where i have a small exhaust leak I see black soot so it makes sense.
Well today, we had like a drastic drop in temperature, now whenever I boost im the farthest led in the red running lean. I let off cause I didnt feel the boost kicking in like it did. I dont see how cold could kick me from runnning so rich to so lean, did the fmu break on me or maybe the a/f gauge. It still cycles back and forth.
Could it be the O2 sensor? I suspected it of going out slowly due to bad mileage, but wouldnt it through a code. Tomorrow Ill thro on fuel gauge to find out what fuel im getting in boost. Also I have a brand new wallbro pump. hear it whining, and stock injectors.

get a wideband

Originally posted by ScreaminE
get a wideband

Yea i was thinking maybe getting one for christmas, problem is I have to wait to then and would like to boost before then.

Deff need a wbo2, But if its cold out, it could be taking longer for your o2 to heat up since it is a heated o2 sensor and the gauge would read its still lean. I am not 100% sure on this, but it seems to make sense since those nbo2 a/f gauges SUCK.

Originally posted by eclipse982nrRST
Deff need a wbo2, But if its cold out, it could be taking longer for your o2 to heat up since it is a heated o2 sensor and the gauge would read its still lean. I am not 100% sure on this, but it seems to make sense since those nbo2 a/f gauges SUCK.

Alright so I hooked up the fuel pressure gauge that comes with hahn kit. At idle i got like 55-57, hard to tell on that crap gauge. Went for a ride, it didnt change at all, didnt even move really. I wonder if the gauge is useless or my fmu is bad. Any ideas?

Originally posted by DarkEclips96

Originally posted by eclipse982nrRST Deff need a wbo2, But if its cold out, it could be taking longer for your o2 to heat up since it is a heated o2 sensor and the gauge would read its still lean. I am not 100% sure on this, but it seems to make sense since those nbo2 a/f gauges SUCK.

Alright so I hooked up the fuel pressure gauge that comes with hahn kit. At idle i got like 55-57, hard to tell on that crap gauge. Went for a ride, it didnt change at all, didnt even move really. I wonder if the gauge is useless or my fmu is bad. Any ideas?

i thought fuel pressure on stock injectors was supposed to be around 45? i dont know though for sure. your a/f gauge is deff almost useless as all it really reads is stoich from the ecu.

Ok lets start simple.

1. On the FMU, make sure you have a good vacuum line going directly to the intake. No t's off other vacuum lines. No weak colored line either, make sure it is stiff quality line so it wont flex with boost.

2. Test your fuel pump, with the engine idleing pinch off the return line from the FMU with a pair of pliers. Watch the fuel gauge, it should rise very fast and the engine might stumble. that is normal.

3. During colder weather the air is more dense, meaning more air particles per volume. This requires more fuel. so running lean can be expected. I have not seen anyone including myslef run lean with a 12:1 FMU though. i dont think your setup is rising the fuel pressure enough.

Test those and make those adjustements and get back to us.

A wideband is nice but with 6psi and FMU style fuel, its not really worth it. If your going to upgrade and run higher boost and start fuel tunign with SFMU or another style fuel setup then buy one.

Terry

Ok so I checked the vacuum line, seems solid, has its own port off manifold, no kinks or anything. Did that pinch thing on return line, could hear the pump make a wierd noise and the engine stumble a little. I dont have fuel gauge right now cause the one I had was ruined today.

Originally posted by DarkEclips96

Originally posted by eclipse982nrRST Deff need a wbo2, But if its cold out, it could be taking longer for your o2 to heat up since it is a heated o2 sensor and the gauge would read its still lean. I am not 100% sure on this, but it seems to make sense since those nbo2 a/f gauges SUCK.

Alright so I hooked up the fuel pressure gauge that comes with hahn kit. At idle i got like 55-57, hard to tell on that crap gauge. Went for a ride, it didnt change at all, didnt even move really. I wonder if the gauge is useless or my fmu is bad. Any ideas?

That is why you are running lean. Check all your vacuum lines to make sure they are all still hooked up. Your fuel pressure should rise 12psi for every pound of boost with a 12:1 FMU. You should be running around 100 to 110 psi of fuel pressure at 7 psi of boost if you are still running the stock injectors.

Update, threw a cel today, checked it, it was 12-21-55.

Originally posted by DarkEclips96
Update, threw a cel today, checked it, it was 12-21-55.

therefore..you have cel code 21:
Upstream H02S stays at center
Harness and connector / Upstream HO2S

Originally posted by XMasta19

Originally posted by DarkEclips96 Update, threw a cel today, checked it, it was 12-21-55.

therefore..you have cel code 21: Upstream H02S stays at center Harness and connector / Upstream HO2S

Anywhere I can buy oem replacements without going to dealership or should I just wait and get it from oxygensensors.com?

Edit: Also could this stop my fmu from rising the fuel pressure in boost?

Originally posted by DarkEclips96

Originally posted by XMasta19

Originally posted by DarkEclips96 Update, threw a cel today, checked it, it was 12-21-55.

therefore..you have cel code 21: Upstream H02S stays at center Harness and connector / Upstream HO2S

Anywhere I can buy oem replacements without going to dealership or should I just wait and get it from oxygensensors.com? Edit: Also could this stop my fmu from rising the fuel pressure in boost?

you can get direct replacements from advanced auto parts, atleast in Ohio you can.

and no, an o2 sensor will not stop your fmu from rising under boost.

Ok just did the 02 sensor, but i still dont know what could be the problem. Only thing I can think of is my fmu not being up to par. I did what star told me to do, those checked out fine.

Well If you had a FP Gauge you'd pretty much be able to tell if the FMU is doing it's job. I sure they can take a crap on you just like any other mechanical part so get an SFMU and have a liiiittle bit more control over you fuel system.

Originally posted by Blizare
Well If you had a FP Gauge you'd pretty much be able to tell if the FMU is doing it's job. I sure they can take a crap on you just like any other mechanical part so get an SFMU and have a liiiittle bit more control over you fuel system.

Well the one i had hooked up b4 it broke was reading like 57 psi and it wouldnt change at all really. Im wondering if my fuel pump isnt the problem. It makes the whining noise but also like a gargling noise, i dont know how to decribe it. Ill take the fmu apart this weekend and see if anything wrong there.

Well ya, take the FMU apart and see if anything is wrong. Then look into the Fuel pump. It's GOT to be one of the two.

Either the pump isn't flowing enough to raise the pressure or the fmu isn't working to actually adjust the pressure.

But if it is just staying at 57psi I would NOT be boosting it.