Data Scan ?'s
Thread Starter
TECH Veteran
Joined: Apr 2008
Posts: 4,985
Likes: 112
Data Scan ?'s 1996 Impala SS
383 H/C, 30 lb FI, 160 stat, EGR & CATS
I have a Actron OBD2 scan tool. I use it to read codes and confirm IM monitors are ready for smog tests and check out 02 function. It does "data stream" several monitors but for the most part IDK what some of it means in terms of if the readings are good/normal or??
I wrote down readings at idle (800rpm +/- 25 rpm) and at 2500 rpm.
The long & Short Term Fuel Trims (%) change depending on rpm but IDK if what my tool reads is normal or?
So here is some data if someone can comment on the STFT
Idle: 800 rpm (+/- 25 rpm)
coolant:185 degrees
IAT:155 degrees
Timing ADV: -24 degrees
MAF (lb/m): 1.23
MAP (" HG): 11.8
LTFT 1: -10.9%
LTFT 2: -6.3%
STFT 1-1: .0%
STFT 1-2: 4.7%
STFT 2-1: .0%
STFT 2-2: 4.7%
O2 1-1: .050-.750
02 1-2: .800
02 2-1: .045-.810
02 2-2: .800
2500 rpm
Timing ADV: -40 (??? seems a lot but is in low 30's most of the time on rev)
STFT 1-1: 11-13%
STFT 1-2:0-3%
STFT 2-1:11-13%
STFT 2-2: 0-3%
02'S
All 4 fluctuate up/down quickly from .050-.820
383 H/C, 30 lb FI, 160 stat, EGR & CATS
I have a Actron OBD2 scan tool. I use it to read codes and confirm IM monitors are ready for smog tests and check out 02 function. It does "data stream" several monitors but for the most part IDK what some of it means in terms of if the readings are good/normal or??
I wrote down readings at idle (800rpm +/- 25 rpm) and at 2500 rpm.
The long & Short Term Fuel Trims (%) change depending on rpm but IDK if what my tool reads is normal or?
So here is some data if someone can comment on the STFT
Idle: 800 rpm (+/- 25 rpm)
coolant:185 degrees
IAT:155 degrees
Timing ADV: -24 degrees
MAF (lb/m): 1.23
MAP (" HG): 11.8
LTFT 1: -10.9%
LTFT 2: -6.3%
STFT 1-1: .0%
STFT 1-2: 4.7%
STFT 2-1: .0%
STFT 2-2: 4.7%
O2 1-1: .050-.750
02 1-2: .800
02 2-1: .045-.810
02 2-2: .800
2500 rpm
Timing ADV: -40 (??? seems a lot but is in low 30's most of the time on rev)
STFT 1-1: 11-13%
STFT 1-2:0-3%
STFT 2-1:11-13%
STFT 2-2: 0-3%
02'S
All 4 fluctuate up/down quickly from .050-.820
TECH Resident
Joined: Jun 2013
Posts: 853
Likes: 32
From: Kernersville, NC
A single snap shot doesn't say all that much. You need to view the data in "chart" or "histogram" format.
Your short terms are always going to be moving if everything is in working order. They will constantly cycle positive/negative....as they are always dancing on the 14.7:1 stoich line(lean, rich, lean, rich, lean, rich....it will look like a sine wave). If they are ever stuck in a positive or negative constant value, then long terms will start to adjust in order to bring the short terms back to cycling lean, rich, lean, rich, lean.....
I am puzzled as to why there are 4 of them showing.
Something unrelated here, but I know that windows Autotap does not display the bank 2 long terms correctly.
Have a look at this....around the 40min mark is an excellent live demo on a vehicle of how they work.
Your short terms are always going to be moving if everything is in working order. They will constantly cycle positive/negative....as they are always dancing on the 14.7:1 stoich line(lean, rich, lean, rich, lean, rich....it will look like a sine wave). If they are ever stuck in a positive or negative constant value, then long terms will start to adjust in order to bring the short terms back to cycling lean, rich, lean, rich, lean.....
I am puzzled as to why there are 4 of them showing.
Something unrelated here, but I know that windows Autotap does not display the bank 2 long terms correctly.
Have a look at this....around the 40min mark is an excellent live demo on a vehicle of how they work.
Last edited by ACE1252; Sep 11, 2017 at 09:35 PM.
Thread Starter
TECH Veteran
Joined: Apr 2008
Posts: 4,985
Likes: 112
yeah a single grab of data is really not the tell all. The tool will log and record. I have the laptop app where I can see the data on various graph form. Just have not used the tool for that function yet
The STFT show somewhat high at idle but do zero out once rpm is raised.
I will lower my FP 1 lb while I have the tool hooked up to see if that changes STFT reading at idle. Right now my FP is 43.5 with vac line off at idle which to my understanding is "spec"...
The STFT show somewhat high at idle but do zero out once rpm is raised.
I will lower my FP 1 lb while I have the tool hooked up to see if that changes STFT reading at idle. Right now my FP is 43.5 with vac line off at idle which to my understanding is "spec"...
