I've been able to gather alot of information from fellow members of this site and other sources books etc.... I'm determined to figure this out I've worked on cars for years and I have plenty of knowledge so I'm not starting with nothing but when it comes to tuning and being able to identify different things from just looking at a data stream I need some work ..I'm sure it will get easier with experience.. but if someone can point me In the right direction or can share some knowledge I would greatly appreciate it ..I figure if I can get the understanding of the perimeters of the sensors at idle I can play around with a few cars i have already to get a further understanding ..

I DO HAVE ACCESS TO TUNERPRO RT I WILL ATTACH A FEW SCREEN SHOTS SO I CAN POINT out A FEW THINGS IM TRYING TO FIGURE OUT

THANX !!!!

 

I have the understanding of
o2 sensor and how it operates (0-1v)

WHAT DOES THE O2 CROSS COUNTS ??

IAC STEPS ?? AND NOT VOLTAGE READING



same with the MAF READINGS 5V REF BUT THE GPS IM NOT SURE AS TO WHAT IT SHOULD READ AT IDLE AS WELL

THIS IS A 88 IROC THAT I JUST GOT RUNNING HAS VACCUM LEAKS AMONG OTHER THINGS JUST WANYED TO GET SOMETHING TO LOOK AT FOR LEARNING PURPOSES

 

is ther conversion tables or anything that shows the perimeters at certain temps , rpm or tps % ?

 

there's a lot of sticky threads at the top of this forum that have a TON of info -- you might want to spend a day or two reading those, they will answer a bunch of questions

 

If you know you have a vacuum leak, go fix that first. No need for electronic diagnostics if you know the problem, they are for when you don't know.

O2 cross counts tells you about the frequency of the sine wave produced by the O2 sensor. No or very few cross counts means bad or dying sensor.

See that "Open" Loop Status? The ECM is not even using the O2 sensor sensor reading in this shot. You're not warmed up, and you might be in limp mode because of the air leak, if you aren't that will go to "Closed" after a couple minutes.

 

It looks like the definition file hasn't been programmed correctly to show MAF grams per second. One of the problems you will have initially is being able to tell real data from garbage data as is the case with that airflow number. That's a useless number. You either need grams per second, or you need MAF voltage and the table that converts it to grams per second. The generally accepted "rule of thumb" is that you want to see about the same number of grams per second as the engine has in liters of displacement. So if it's a 5.0 liter engine, generally speaking at a warmed up 650 RPM idle you should see around 5 grams per second. This varies according to idle speed of course and engines with fewer cylinders tend to have higher readings due to higher idle speeds required to maintain smooth operation.

Cross-counts is a narrow band O2 thing. It has to do with the closed loop fuel calculations - the ECM bounces back and forth - hovering above and below stoich - which is 14.7, or 0.5v. This is on purpose as maintaining a constant 14.7 is not conducive to 2-way and 3-way catalyst operation. The cross counts give you an idea of how rapidly the O2 is cycling, and thus it's response time. As they age they get slow to respond.

IAC steps is another one you just have to know what's normal. It is generally accepted that you want to set the idle stop so that at warm idle you have about 20 steps on the IAC. Zero steps is fully closed. You don't want the IAC closed (means the throttle is propped open or you have a vac leak), and you don't want it way, way open either as that area is needed for cold idle operation. You want it "just right" - which in this case is about 20 steps when warmed up.

When in closed loop, BLM and INT become more important. Those are your long term and short term fuel trims respectively. 128 is "zero" trim. Less than 128 is a negative trim (subtracting fuel), and more than 128 is a positive trim (adding fuel). Most ECM's can't go lower than 108, or higher than 160.

GD