VikingTrad3r

guys,

i have this crap idle and stalling out issue on my 85. i've done the basics like cleaning the tb and checked for vacum leaks (though that should give me high idle not low idle) and tapped the maf and the egr.

my question for you guys is im really tired of chasing this thing, and i just watched an amazing video showing how the FUEL TRIMS will tell the story as to if the engine has a lean condition or a rich condition which will allow me to rule out a bunch of things.

for example, if i scan my 85 and i see that the ltft is negative, i think that would tell me i have a rich condition so either not enough air getting in due to some blockage or (more likely) injectors oversupplying fuel issues. did i get that right? im tired of spending money on parts and i just want to learn how to read a scanner.

here are the videos i watched.


and


edit: very strange, most of my post was deleted when i pressed the post button. strange.

VikingTrad3r

and a further question, does the 1985 corvette (and other early models, i also have an 87) work with this cable?

http://www.aldlcable.com/products/aldlobd1u.asp

it says:

"This cable works on cars that have the serial data pin on pin M or pin E of the GM 12 pin OBD1 ALDL connector, which is most every 1982 to 1995 GM car. Pin M indicates 8192 baud and pin E indicates 160 baud rate serial communication speed."

Cliff Harris

That should work with the correct software.

Some cars put out 160 baud on pin E and when 10K is applied across A & B they put out 8192 baud on pin M. Corvettes don't have a pin in cavity M so this does not work.

Corvettes put out 8192 on pin E after the scan tool sends the correct "key" code to start 8192 baud mode.

Ronaldo

I'm using that cable for my 1987 vette (with Tunerpro and TTS Datamaster). Isnt the 1985 ECM only capable of 160 baud? (equal to 160 bit per second, which would correspond to 20 byte per second)

VikingTrad3r

i know that the 85 ecm processes information slower than the later cars, but i do not know if this same feature restricts the communication through the scan tool or if it would inhibit the ability for the scanner to function with the 85.

is that what you were meaning? will the 85 still be accessible with this cord and a pc program (tunerpro, datamaster, winaldl) and display the data even though its ecm is slower than the later years?

VikingTrad3r

https://www.youtube.com/watch?v=dnRh...ature=youtu.be


man this guy is speaking my language. i want to be able to understand a how to read this stuff for all my cars. expands my brain, a new model of learning i can apply to other areas of life, and will make owning high mileage cars so much cheaper!

Ronaldo

Just meaning that it will be slower.

http://tpiparts.net/ecms_and_proms/

Cliff Harris

The '85 ECM does not process information slower than later cars, but it does COMMUNICATE more slowly. ...And the number of parameters that are transmitted is lower.

VikingTrad3r

thanks for clarifying guys. will there be fuel trims with the 85?

VikingTrad3r

bump. anybody know if there are fuel trims that come out from the 85ecm?

Also, i just ordered my cable. thnx, now to find the software.

Cliff Harris

It reports fuel trims but doesn't tell you which one it's reporting. You have to look at RPM and the other parameters and figure it out.

DanielRicany

There is one oxygen sensor on an 85. That is on the drivers side and that is the only side the ECM monitors for fuel correction, and corrects the whole engine based off of that sensor.

LTFT is a term commonly used in OBDII systems. It means Long Term Fuel Trim. And also STFT which is Short Term Fuel Trim.

In OBDI, we used something different to identify long term and short term fuel trims. Those are called BLM and INT. BLM is long term and INT is short term. On an '85 INT is virtually useless, and I never look at short term fuel trims anyway because they are always going to be moving regardless of if there is a problem or not. Long term fuel trims, or BLMs, are much better to monitor fuel trim status, as it tells you how the ECM is correcting fuel over a longer period of time. BLM can change at the same rate as any other parameter on the 85 ECM scanner data. So it updates fairly quickly.

128 BLM means that the ECM is not adding or removing anymore fuel in comparison to what the MAF sensor is telling it. Meaning that 128 is perfect. Higher than 128, the ECM is adding fuel. Lower than 128, the ECM is removing fuel. The minimum and maximum BLM figures are 108 and 160. At 128 BLMs, +/- 10 is acceptable in my opinion, and would not make me think anything is wrong with the car. Any further and there is a problem somewhere.

VikingTrad3r

sweet, do you use tunerpro or tunerpro rt? and why?

also, i am off to figure out if i need an 85 definition file, i assume that is a .bin file.

VikingTrad3r

Daniel,

Just want to say thank you very much for taking the time to write this. It will give me a heads up to get started. My immediate aim with tunerpro (not sure if i need rt or normal tunerpro yet) is to see if i have high or low fuel trims. i guess based of your description i will only be looking at long term corrections. i assume that the issue with the short term, or INT as it is called, is because the 85 computer is too slow? or is it the issue of only one o2 sensor?

anyway, i would like to get sorted out straight away in figuring out if i am rich, or lean.

i had thought i have a brake booster leak, (sometimes i get a slight whistle when stepping on the brake) and when i am going very slow, say backing into a stall, the car konks out. i was going to look for the change in short term fuel trims showing a difference when my foot is on the brake. i guess for the 85 that is out the window!

thanks again.

Cliff Harris

The .BIN is the actual binary code that the ECM executes. You need this to make modifications. The process is: read .BIN (or get one from somewhere), make changes, write .BIN to EPROM, plug in EPROM and run.

The definition file tells the software what parameters the ECM is sending (like RPM, etc.). It is an .ADS or .ADX file. The original format was .ADS but it was upgraded to .ADX. An .ADX file allows you to configure and save software instrument panels.

VikingTrad3r

Thank You Cliff!

So I will need a definition file for my 85, and then one for my 87 as well? Seperate files because the number and position of sensors are different and the ecm is different?

honestly i cant wait to get my hands on scanning this 85.

Cliff Harris

Yes.

The .ADS files are text files. You can read them with a text editor like Notepad.

My preferred method is to make a shortcut to Notepad and then put the shortcut in the SendTo folder. Then you can right click on the .ADS file and SendTo Notepad.

If you want to be really tricky you can make a shortcut to the SendTo folder and then put that in the SendTo folder. Then you can SendTo any application you want to the SendTo folder.

VikingTrad3r

thanks for the tips.

i have my 85 files already sourced here:
http://tunerpro.net/downloadBinDefs.htm#GM

VikingTrad3r

cable arrived today.

lets make this happen.

i have my 85 ads and xdf file.

tuner pro is installed, here we go.

my understanding is that bin files are used to write to proms? i will not be doing that yet. right now i want to get real time scans to see if everything is reading correctly, specifically blms to diagnose my junk closed loop idle.

here we go!

VikingTrad3r

ok, winaldl at least recognized there was a cable attached to it. set it to 4800 baud with the right 85ecm and not getting any blm numbers. i get the first 5 lines in the raw data table and thats all.

anybody?