Patrick G

iTrader: (14)

A little background. My car has been beautifully tuned with Speed Density closed loop. L-trims turned off. I monitor my S-trims all the time and rarely do they stray more than +/- 2%. My tune is razor sharp.

Today, all of the sudden, both NB O2 sensors went wacky giving me -30% and -40% S-Trims in almost all my cells. Even at idle (where I'm used to seeing 0% s-trims, they're running -25% or greater. The motor starts fine and when the O2s come on line, they show low percentages. But after some driving, they creep up to the -30s and -40s.

Here's what I've checked:
MAP sensor seems to be functioning properly.
IAT sensor is reading accurately.
TPS sensor is working properly.
I've made no changes to the tune.
Both NB O2 sensors (Bosch 13111) show the same data.

I haven't checked fuel pressure.
What in the world could cause my S-trims to jump like this? This tune has held solid for around a year. Why would it change drastically in 1 day?

TAQuickness

iTrader: (28)

Check your email...

mikey

iTrader: (6)

Patrick, what OS are you running?

Patrick G

iTrader: (14)

Still running stock '00 OS along with Roadrunner Emulator.

HavATampa

iTrader: (49)

My s-trims went wild to the negative side one day before I was planning on swapping out a slowly dying battery and alternator. After the electrical upgrade, all is well again with the s-trims. Dunno, something to look into. If the o2's aren't getting the juice they need, could make the readings inaccurate.

MSGHUFF

iTrader: (7)

Patrick, some dumb things to check: make sure your air filter is clean and no blockages in the intake track ie plastic bags/road trash. Fuel pressure and as stated earlier Batt voltage

Patrick G

iTrader: (14)

Air filter is clean. Fuel pressure is steady. Battery voltage is something I'm going to need to watch. It's hanging in the high 12s and low 13s when running. I'd like to see it higher than that personally. Crazy thing is that the s-trims start off a 0% when I first start the car (even after warm starts). But gradually, they start shifting to the negative. On Sunday, I'll hook a wideband to it and report back. Keep the ideas coming.

Special thanks to TA Quickness, WS6FirebirdTA00, and 98 Aggie for their help over the phone today too. I'm narrowing down the variables one by one!

ZL1Killa

iTrader: (17)

let me know how that goes. i'm curious about that

Patrick G

iTrader: (14)

Wide band shows A/F ratio still at 14.7 so they're doing their job (by pulling fuel). I replaced the MAP sensor and sealed it up really well. No change. Replaced alternator. No change. Battery is next. This problem is getting expensive to diagnose.

Steel Chicken

iTrader: (3)

got a log you can post so we can look at it?

Patrick G

iTrader: (14)

Too much data. It would be over 20 items and over 3000 frames. I can e-mail the file if you want to look at it.

TAQuickness

iTrader: (28)

That was quick! Did your voltages get any better after the replacement?

Patrick G

iTrader: (14)

Yeah, Andy I don't like waiting. The voltage started off better, but it eventually went down to the low 12s. I suspect my Optima red top has seen its better days. I think I'll exchange the battery and take the alternator back and get a higher output one. This stock replacement can't keep up with the EWP, Racetronix fuel system, dual fans, AC, and headlights all at the same time.

TAQuickness

iTrader: (28)

Gotcha. Check your email. I sent you a link to an alternator shop in Dallas. I ordred a 200 amp'r a few minutes ago. puts out 100 amps at 800 rpm, has a 2 year warranty and should be on my front porch by friday.

ZL1Killa

iTrader: (17)

100amp at 800rpm!!!!!!!!!!!!! nice.

Steel Chicken

iTrader: (3)

high 12's seems pretty low for a running vehicle. id also place my bet thats an issue.

Slowhawk

iTrader: (12)

Add in a voltage booster.That way you can set the voltage at 14volts or so.

Patrick G

iTrader: (14)

Where can you get one of those Don? Will I need something better than the stock 102a alternator to run it?

Rob

iTrader: (6)

Caspers Electronics should have/make one.

Patrick G

iTrader: (14)

This is just too wierd. Can't figure out what's making this happen?

MAP sensor swapped and sealed.
Vacuum hoses checked.
Alternator swapped.
Battery charged (not swapped yet, but voltage is good).
Fuel pressure steady at 63 psi (Racetronix pump).
Narrow band O2 sensors working well (Bosch 13111 C5 rears).
Wide band O2 sensor shows good fueling at all temps, but S-Trims continue to be in the -20s and greater after the car warms up. When cold, they're good. Pretty close to 0%. Nothing has changed with the tune. S-Trims used to stay rock steady at +/- 1-2% at all rpm and MAP readings when fully warmed up. Anyone else have any ideas?