Ok guys a few questions...
I installed a 99 L67 with a 4T65HD on OBDII programming from Lloyd. Using ScanXL I have LTFT bank 1 and LTFT bank 2. Which one should I be using? Under full boost I am reading +5.5 bank 1 and -2.3 bank 2. Is this Ok?

Also, If I punch it from a dead standstill it is either missing or having trouble going from 1st to 2nd. No missfires reported. It almost feels like a rev limiter kicking in??? If I punch from a rolling start I have no issues. Any ideas??

quote on OBDII programming from Lloyd.

All I can say is good luck.

Doesnt sound mechanical to me. You should not have the ability to scan 2 banks, as you only have 1 o2 sensor.

An OBDII V configured engine has 2 banks.
Bank 1 is always the bank with cylinder 1.
Bank two is the other one.
That engine originally has 2 02 sensor's before the cats for fuel control/feedback.
Don't worry about the trim's being a little different.
The short term trims are what are happening righ tnow at this moment.
+ means it's adding fuel over baseline,or lean
- means it's pulling fuel from baseline,or rich.
The long term trims are the computers learned response over time.
Add the two together to get your total fuel trim.
short term trim's will generally bounce from zero to +/- 5% ,this isn't a problem.
It's the computer adjusting to variable conditions like temp,density etc..
Where you have an issue is when you are deviating from the -/+ 5% of baseline.

quote Originally posted by DefEddie: An OBDII V configured engine has 2 banks. Bank 1 is always the bank with cylinder 1. Bank two is the other one. That engine originally has 2 02 sensor's before the cats for fuel control/feedback. Don't worry about the trim's being a little different. The short term trims are what are happening righ tnow at this moment. + means it's adding fuel over baseline,or lean - means it's pulling fuel from baseline,or rich. The long term trims are the computers learned response over time. Add the two together to get your total fuel trim. short term trim's will generally bounce from zero to +/- 5% ,this isn't a problem. It's the computer adjusting to variable conditions like temp,density etc.. Where you have an issue is when you are deviating from the -/+ 5% of baseline.

You have one 02 before the cat (in the rear manifold) and one after the cat. The rear 02 has nothing to do with your fuel trims, does not affect fueling at all, it's just there to make sure your cat is functioning properly. I've never seen a 3800 with more than one pre-cat 02 sensor before.

Checked the service manual for my wife's impala,it is indeed a single 02 sensor.
Sorry for the confusion.
Almost all OBDII systems I work on have a front (sensor 1) HO2S for each bank. (granted I am a Ford tech,not Chevy)
(exceptions I have seen are LEV's and ULEV's which use 2 02 sensors on a single 4cyl bank plus a cat monitor).
I mainly tune chevy trucks and f-body's,not alot of smaller engines.
The trucks,camaro's and GTO's all utilize a single 02 sensor in each bank along with a single monitor on each bank.
That's a total of 4 oxygen sensors.

And the front 02's are for fuel control/feedback and the rear are simply monitor's checking cat efficiency as mentioned.
Rear 02's are used for slight long term fuel adjustment,but it's like 1% of total fuel trim over time.
As far as I know only chevy uses the rear monitors for this type of control,not anything to worry about if they are deleted.


You still want to add together the short term and long term trims for total fuel trim.

It is quite easy to turn on the second o2 sensor, and wire it on most any 3800 code, as the 3800 camaro's used 2 o2 sensors.

It has been turned on before, but its fairly impossible to run dual o2 sensors without knowing it.

I need to reproduce the failure again and really pay attention to the gear and the RPM. It never does it from a rolling start, only from off the line and it feels like a rev limited is kicking in preventing it from shifiting from 1st to 2nd.

There are two fuel trims the LTFT (Long term) and the STFT (short term) . You want to focus on the LTFT's. Ideally these should be as close to zero as possible but if the LTFT is within +/- 5 then you are within the acceptable range. GM says +/- 10 is OK but racers want to keep the numbers closer to 5. A more important reading will be the wideband O2 sensor readings. Being in the 11-11.5:1 range at WOT at full boost is probably where you'll need to be for the best power and lowest KR.s
Also keep an eye on KR's;. The engine can cope with a couple of degrees but you really don't want any at WOT.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

The PCM isnt native to the motor and I havent done a case learn yet and I wonder if this could be an issue. The fuel trims according to what you said look fine.

would make SOME sense... depending on what code genius loyde used, you could be in spark fault mode, which would give you that type of timing.

There will be a code asking for case learn (or another spark related sensor) that you will just need to fix to fix the spark fault mode. "typically" in the code I use, spark fault comes along for one of a few reasons, and shows it self as KR, in a really interesting multiplicative way which lets you get more than 14 degrees of actual spark retard. KR in its raw form only limits up to 14 degrees of timing.

Another "typically" in the code I use, no case learn will not cause the car to run any different than any other car... its just it will not detect knock or misfires.

Thats the funny thing. Im not throwing any codes or setting the light. I just punch it and the car timing drops to zero for a second then picks up and runs. It definatley feels like rev limiter.

There is a timing limiter that sets to 0 timing.... I set it near redline on all of the cars I tune.... On the automatics its to help shifts, and on the manuals its a soft limiter to help keep you away from the 7000rpm fuel cut.

I think I need to log the misfires to see if its a wire or a plug on a specific cylinder. Here is my data when the engine cut out.

# Time LONGFT1 MAF MAF VSS MPH SPARKADV IAT F RPM ECT F O2SV MAP inHG

353 18:40.0 2.3 21.35 161.42 45 -0.5 86 3427 180 0.845 32.2

Just an FYI, only '97 PCM's will show timing in negative numbers. On the '97 PCM's you don't have to do a CASE learn as long as the original knock module (attached to the PCM with two screws) is kept with the car/engine. Being that you have a '99 L67, you have two problems here. 1, you will need a case learn because that PCM doesn't go with that engine. 2, the '97 PCM's detect knock differently than the '98+ PCM's (analog vs. digital). So you're either going to have to replace your '99 L67's knock sensors with ones from a '97, or go to a '98+ PCM (the better route if it isn't too much work for you).

I know for a fact the PCM is from a 99 GTP and there is no modules attached which makes this even more odd>>>

digital and analog knock detection? Where did you get that one from?

I am running 1 97 knock sensor and 1 96 dohc knock sensor on my car... works fine with my 98 pcm.

I know you will have about a 50/50 chance of needing a case learn, typically it works, sometimes it doesnt.

Just for giggles I am going to have the case learn done today at a local shop and see if that helps. I dont think its KR pulling the timing b/c it all comes back at once within a 10th of a second. This is weird. Im going to have the guys pull any trans codes today when they do the learn to see if its mechanical.

The trans codes sit on the pcm, the same place as the engine codes.

Dark is right on about the case learn. You may need to do the Crankshaft Position Variation Learn procedure. Its basically following the procedure for correcting DTC 1336 - Crankshaft Position (CKP) System Variation Not Learned. As far as I know if the DTC doesn't show up (and its still enabled) you're OK and if not then you will need to find someone with a Tech 2 or high end Snap On scanner. Its only a short procedure but there is no way around it, just be sure that whoever does the case learn doesn't do a full reflash or you will put the PCM back to the stock settings.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

HPT, DHP, and areoforce interceptors all do case learns.

Ok, I had the case learn done today and that went smooth but still no go on ironing out the issue. I punched it on the interstate and at the top of each shift it pulled the timing before going into the next gear. No trans codes, no dtcs. ?????????? This is killin me. Normal driving and mild agressive driving is a non issue. Just WOT issues.

quote Originally posted by darkhorizon: digital and analog knock detection? Where did you get that one from? I am running 1 97 knock sensor and 1 96 dohc knock sensor on my car... works fine with my 98 pcm. I know you will have about a 50/50 chance of needing a case learn, typically it works, sometimes it doesnt.

Maybe you've heard about the '97 GTP's mystery KR problems? A lot of guys were swapping the PCM/wiring harness to the '98+ style because of the PCM. The way the PCM's read knock is different, this is why they have different sensors (IIRC, it may just be the PCM that reads the sensor differently).

I know because I had a '97 GT that was having this KR issue a long time ago, so I did a lot of research, and I was about to go with the newer harness/PCM setup. Check it out on clubgp if you don't believe me.

To the OP, i've never heard of timing being shown in negative numbers on than from a '97. Was it just that one line that came out with a -0.5, or are all your timing values -XX?

Only one line was -.5 everything else is positive. The first time it occurred it pulled the timing from 20 to 4.

quote Originally posted by anwalker: Only one line was -.5 everything else is positive. The first time it occurred it pulled the timing from 20 to 4.

Without looking at your .bin i'm not sure how much anyone is going to be able to help you. Sounds like an issue in your PCM (possibly TQ management), not something mechanical, as darkhorizon already pointed out. Doesn't sound like you have access to your .bin, though.

I have a 97gtp and I have disabled knock sensors on a 96 before as they would just peg to 14 degrees the entire time you had your foot on the gas.... Its all sorts of no fun.

I dont believe they actually "changed' the way it was read or not read from analog to digitial.... I think it was just a simple amount of tweaks and changes to make it work better. If the sensors are indeed different, they were extremely close in design

So many variables. This is driving me nuckin futs. I need to get this thing to a tuner and Dyno. I dont think its mechanical either since it only happens under specific conditions.

[This message has been edited by anwalker (edited 09-11-2009).]

quote Originally posted by darkhorizon: I have a 97gtp and I have disabled knock sensors on a 96 before as they would just peg to 14 degrees the entire time you had your foot on the gas.... Its all sorts of no fun. I dont believe they actually "changed' the way it was read or not read from analog to digitial.... I think it was just a simple amount of tweaks and changes to make it work better. If the sensors are indeed different, they were extremely close in design

Exact problem I was having, any throttle = 14.67* KR, even with the sensors disconnected. Only time I didn't get KR was at WOT. Talk about frustrating. There was talk of trying to use an LT4 knock module on the '97 PCM and see how that worked, but I don't think anyone ended up trying it.

Sorry to derail the thread anwalker.

Well, just flash a file that disables knock detection under 5600 rpms.