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Joined: Oct 2000
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Mr. Munson....overthinking as usuall Yep, hit that nail on the head, Judge. Always driving that train  PA3L: codes I got were P1131 (bank 1 lean yada yada) and P070 (bank 1 lean yada yada). Unfortunately in my haste to explore the nether regions of OBDII, I managed to accidentally erase the freeze data. Oops. Anyway, doing a little search on these codes, it seems like the upper rear 02 is on the blink, or maybe the connector is acting up. Anyone know where I can rent a midget to get back in bank 1's exhaust manifold? Car is a 99 SE Duratec MTX w/40k miles, Borla/Magnaflow exhaust, KKM, and no other engine mods. Thanks for the information guys. It's good to see intelligent posts that are devoid of the usual high school banter about spoilers and big wheels.
-Kurt
"I'm a little sceptical of that internet thing. After all, what's it got besides information?"
-DB, 1/97
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Joined: Jun 2002
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aaaaahhhhh... so confused. want to know.. but brain just did an overload... get the jumper cables..
Licence plate - ITOW5L
family car... why YES it is .. and you just lost.. oh ... so sorry..
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Joined: Jun 2001
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Originally posted by DemonSVT:
My ST trim alone is 28-38% (depending on rpm) Actually, I should say "if LT + ST trim goes above 30% absolute in closed loop mode you'll get a rich/lean CEL". I wonder if the chip has any effect on (not) throwing that code. I also doubt you drive much in closed loop mode anyway Demon. 
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Originally posted by HoosierContour:
At WOT it jumps up to 38% ST fuel trim lean. But the 02 takes over at WOT. So the ST is off no value. The 02 values now read either .93 or .94 and .92 at the secondary actuation.
I'm going to clarify this one, because I doubt you really meant what you wrote. Short version: The O2s are ignored at WOT (along with ST trim, even though it is still calculated). Long version: At WOT (or really, any event that causes open loop: high TPS/power enrichment, low TPS/deceleration enleanment, O2s not switching yet when the car is first fired), the ST trims are ignored (but still calculated). IIRC the PCM goes to a Load vs. RPM table and looks up a preprogrammed FI open time. Then it adds the LT fuel trim for the current conditions. LT isn't updated but it is used.
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Joined: Jun 2001
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Originally posted by Munson:
PA3L: codes I got were P1131 (bank 1 lean yada yada) and P070 (bank 1 lean yada yada). Unfortunately in my haste to explore the nether regions of OBDII, I managed to accidentally erase the freeze data. Oops. Anyway, doing a little search on these codes, it seems like the upper rear 02 is on the blink, or maybe the connector is acting up. Anyone know where I can rent a midget to get back in bank 1's exhaust manifold?
I'd list the possible causes from the manual for P1131, but the first paragraph really says it all: Diagnostic Trouble Code (DTC) P1131 bank 1 (Cylinder 1) indicates the fuel/air ratio is correcting rich for an overly lean condition. The HO2S voltage is less than 0.45 volt. Hook up that scan tool after taking about a 10 minute drive. If the O2 value on Bank 1 isn't oscillating around 0.45 (instead staying below 0.45) then you've found your problem. Bad sensor or bad connection. Dunno what to say about the other code (it's missing at least one digit).
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Originally posted by HoosierContour:
I found this informative.
Before starting to tune WOT, it is a good idea to hook up an OBD-II scanner (like Autotap) and monitor the STFTs and LTFTs for both bank1 and bank2.
The LTFTs give you a very good idea of how your system has "adapted" to your intake/fuel system mods. They are just time averaged STFTs. The maximum deviation of the LTFTs is +/- 25% and demand for anything beyond will throw a code (if STFTs are also > 5% in the same direction). When the car is new, the LTFTs will most likely be less than 5-7% across the entire data array. When tuning the closed-loop system with the MAFterburner our goal is to hit 0% LTFT but anything less than 5-7% in either direction is acceptable.
Let me step back, the LFTFs and STFTs are not single variables but data arrays which vary with load/RPM. Therefore, when you are tuning, you try to run the car at many different load points while monitoring the trims and making adjustments with the MAFterburner's closed-loop table.
The first thing to do is hook up the scanner and drive around monitoring the LTFTs and STFTs. If they are smaller in magnitude than 5-7%, you have nothing to really do. However, if you wanted to get them closer to 0%, you could fine-tune your system using the MAFterburner.
Here is something that I posted on the Corral:
If you have an Autotap (or any other OBD-II scanner) then you can completely recalibrate your MAF to accurately represent your new system yourself. Here is how:
If you have made changes to your intake setup, you may be misleading the PCM into thinking that your car is running richer or leaner than it actually is. The reason is that these changes may have caused the MAF measurement system to go out of calibration and the result is your PCM "adapting" to this faulty information while operating in a closed-loop operating strategy. Provided that there is enough dynamic range left in the STFT/LTFTs, you will not experience a fault condition BUT it may negatively affect your WOT tuning.
This is the reason for CLOSED-LOOP tuning with the MAFterburner System.......to bring everything back into CALIBRATION using the PCM's "adaptive" system as a tuning guide.
More Information:
The STFT/LTFTs indicate just how the PCM is modifying the injector pulse widths to maintain stoichiometric (14.7:1) A/F ratio while running in closed-loop operating strategy. No matter what changes you make to the MAFterburner, the PCM is going to adjust so that it maintains stoich (as long as it doesn't run out of fuel trim). If it runs out of fuel trim (i.e. meets certain criteria), it'll throw a code. The only real reason for tuning this closed-loop system using the MAFterburner's CLOSED-LOOP table is to fix any large deviations in the intake setup caused by aftermarket mods. Why bother with this? Because the "open-loop fuel modifier" is taken from the LTFTs. So, at a given load/RPM condition, if you made an intake change that caused the fuel trims in that cell to richen by let's say 10% (+10%), and you go WOT from that cell, 10% fuel will be added to the calculated injector pulse width and the car will run richer than ideal (on some model years). So, by tuning this closed-loop system to achieve near-zero LTFTs in all cells with the MAFterburner's CLOSED-LOOP table, you are effectively insuring that the OLFM will be zero. The next step is to make the EXACT same changes to the OPEN-LOOP table so that you have a good baseline to work from. That way, you can use the MAFterburner's OPEN-LOOP table to tune WOT on a dyno and you can be sure that the PCM will not have to make any large corrections over-time to what you tuned on the rollers. This may be confusing but let my try to give two examples:
1. Let's say you're on a dyno and go WOT from cell X. In cell X, the LTFT is +10%. So, let's say that the PCM tries to maintain OL a/f ratio of 12.0 and measures the MAF signal and computes the pulse-width to achieve that a/f ratio. However, the PCM adds 10% fuel to this because it "learned" that the car generally runs 10% leaner then demanded when in closed-loop operation. If you haven't messed up the "calibration" of your intake system (i.e. the transfer function in the PCM matches that of your actual system) then you get 12.0:1. However, if you've changed your MAF or added a CAI or made some other changes to throw off the transfer function (MAF is out of calibration), then you don't get 12.0:1, you get 10.8:1 which is too rich.
2. Take the same example as above. Now you use the MAFterburner's CLOSED-LOOP table to effectively zero out the LTFTs across the entire load/RPM range. Now when you go WOT from cell X, you get the PCM's desired a/f ratio of 12.0:1 because the OL fuel modifier is near zero. Natural changes still effect the trims and the system functions as normal (i.e. O2 sensors age, etc.) BUT you have essentially RECALIBRATED your intake tract to precisely match what you REALLY have. No other MAF tuner-like device can achieve this goal!
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In conclusion, the novelty behind the MAFterburner is that it allows the tuner to "correct" for inadvertant changes made to the intake tract (including CAI, new MAFs, cams, etc.) via user modifications. IMO, this tuning method is unique to the MAFterburner system. The tuner uses the PCM's LTFT/STFTs to "see" precisely how the system calibration has been thrown off and uses this information to essentially recalibrate the system. Hey HoosierContour, Boy, it's kind of weird to come over here and read a post about the MAFterburner and say to myself: "That sounds really familiar. Where did I hear that before?" only to realize that heck it sounds familiar because *I* posted that over on Stangnet.com and Corral.net.  Pretty cool that my words have travelled all over hyperspace! Anyway, good find! Hope you like the MAFterburner and if you need anything, just let me know. Cheers, Mark Chiappetta
Zone-5 Performance Products
Creators of the MAFterburnerTM
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'03 Sonic Blue SVT Cobra Coupe
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