i just got a 2002 scsb truck with lq4 swap. i also just got hptuners up and running so i can adjust it. right now the truck runs pretty well, but drinks lots of fuel ie 12.5mpg. i got a ngk wideband connected too and its reading mid to high 11's afr at idle and cruise and getting into the 12's on hard accelleration. i've also got a p0178 engine code as the computer came from a 2002 flex fuel suburban.

so to start out, i'm running extremely rich. would anybody advise on my first corrective actions? should i be looking into my fuel management? disable flex fuel commander from reporting to the computer? other?

i also have captured the current tune on the truck if anybody needs to see that file to help out.

 

What are your fuel trims doing at this point when it is idling so rich?

 

I would start by going to the tune repository and finding a stock tune that matches the year and engine size. Then just compare the differences, copy over what you think better matches your application (i.e. non-flex fuel)

Might want to get the number off of an injector and look up the flow and make sure it's right in the tune.

After getting the base tune correct to start, then I would proceed to tuning VE table, if my fuel trims were high.

Edit, after reading back and seeing that it actually leaned out on hard acceleration, I would think the injector flow data in the tune might be for a non-return fuel system and perhaps you have a vacuum regulated fuel rail. If that is the case you need to set the injector flow the same across all MAP values. Again, see tune repository for non-flex vehicle.

 

i still haven't gotten anywhere on this. i ran a quick log and found my b2s1 o2 sensor was non responsive stuck at 450mv. i replaced it but still getting that reading. i have to trace wires today i suppose.

 

If my records are correct, the pink wire should be hot in run and start position, the black wire should be directly to ground, Purple wire should go to C1 (blue) pin 66, Tan wire to C1 (blue) pin 26.

 

After reading in another thread, apparently there are 2 styles of o2 sensor that will plug into the same oem plug. One is case grounded, the other is grounded through the harness. Just a thought. I honestly do not remember which vehicles they are from though.

 

thanks for info, i was just checking back here to ask those questions and do some searching. my bank 2 sensors have been cut and extended so i'm dealing with someone elses mess. i'll look for my path on signal lines.

 

on my meter with key on i get
black- x.xx
tan - 4.41v
purple - 1.23v
pink - 12v

 

ok, my tan is running to pin 25 and purple is on 66. this is for my bank 2 sensor 1 o2. now i checked the tan for b2s2 and it is running to pin 26.

am i right to switch tan on the wiring? those pin numbers you gave me are for forward o2 sensors correct?

 

https://ls1tech.com/forums/generatio...vette-o2s.html


This may help you with identifying your wires. (Obviously this is for F-bodies, but seems as if your wiring/ecm is very similar) A lot of us F-body guys switch the wires so we can do without buying extensions and just utilize the factory harness. (Basically do the pin swap and the rears become the fronts and will reach long tube headers)

Hope this is kind of what you were looking for.

 

Yes. Sounds like you found your problem.

I have the o2 sensor schematic right in front of me for a 2000 silverado, I assume it would be the same as it can use the same pcm and o.s. I can e-mail you a copy if you pm your e-mail address. I don't know how to post a file.

HO2S Bank 2 Sensor 1
tan - C1-26
PPL - C1-66

HO2S Bank 2 Sensor 2
Tan - C1-25
PPL - C1-65

Added; Bank 1

HO2S Bank 1 Sensor 1
Tan - C1-29
PPL - C1-69

HO2S Bank 1 Sensor 2
Tan - C1-28
PPL - C1-68

 

yes it fixed my problem, truck is running alot smoother now.

next up.....
my ecm came from a flex fuel vehical and my truck is not. i have dissabled the codes i was getting about the modual not communicating. my next question is on my stoich afr commands i get a % table with afr commands per ethanol %. should i change this table to read same value across all cells since i don't use blends above 10%? this is how i see most tunes in repository that are non flex fuel.

 

Yeah, if I remember correctly my non-flex fuel tune just has a single value of 14.69 for stoich afr, not a table. Get the stoich afr correct, and the fuel flow correct and it should be much happier.

 

i used 14.4 as my setting, and my wideband is reading the change. do you recomend i possibly go to 14.69 or stick with the 14.4 since all pumps around here seem to have posible 10% stickers at pump.

 

Maybe I missed it, but which wideband? I know most, unless you are able to calibrate what the stoich value is will read 14.7 when your actual afr is 14.4. So if you are reading 14.4 and it is targeting 14.4 it may actually be closer to 14.0-13.9 even. Confusing I know, but many read this way as it is just a function of lambda, not the true air fuel.

 

This gets a little tricky and I have a hard time understanding.

The way I understand it, the ECM will use data received from the o2 sensors to trim fuel until stoichiometric ratio is acheived, no matter what the fuel is. It is 14.7 for gas, 14.1 for e10. The o2 sensors will see the same voltage at stoich for each fuel mix. It is also likely that your wideband is configured to read 14.7 at stoich for any fuel burned as long as the o2 counts are in the stoich range.

Not sure what to set stoich at, but I would start with a stock non-flex fuel value.

 

Widebands tend to assume straight gasoline and do the
arithmetic for you based on EQ number. We don't have
a good idea what "up to 10% ethanol" means, practically
speaking, pump to pump. I'd settle on one you like, and
tune to lambda rather than the mystery AFR(stoich).

I've never looked at a flex fuel vehicle but wonder if, like
many modes, there's a way to just turn it off and pretend
it's a straight gas tune.

Now 12.5MPG in mixed driving for a heavy square-nose
brick, doesn't sound all that bad; the cammed up Camaro
gives me about 15 and my 4BBL SBC 400 '70s Caprice
delivers a sweet 8MPG (no overdrive).

 

im using the ngk wideband. I believe it displays 14.57 stoich. I hit 14.44 on display at a stop and fluctuate usually between 14.3x to 14.6x at times. if the o2's look for the same stoich regardless of what that is per fuel used, does that mean regardless of my settings, the system will adjust to where it needs to be given commanded afr?

if so then I'm thinking I don't need to compensate for the pumps 10% label and use the factory 14.7. Is this safe? goal for me here is safe and economy.

 

we all love video's, so here is a quick idle clip of my truck

 

You need to have the correct stoich in the tune because the PCM uses that in calculations that determine fueling. I use 14.681005 and do not compensate for E10 that is in the pumps these days. However, I do use lambda to tune so my WOT (open loop) tuning is compensated for blended fuels...