ALDL data logging

[Ricko1966]

128 is base fuel trim lower means the computer is pulling fuel higher means it's adding fuel. If it were adding or subtracting from fuel trim,you'd want to investigate why,bad plug wire,intake leak,leaky injector etc.

 

[YakkoWarner]

128 is base fuel trim lower means the computer is pulling fuel higher means it's adding fuel. If it were adding or subtracting from fuel trim,you'd want to investigate why,bad plug wire,intake leak,leaky injector etc.

Is a slight varience (like 124 to 132) an acceptable range? I did see it go up significantly (like 145ish) for just a second and that -as expected- did trigger the SES light for a minute or 2 before it went back off. Unfortunately that was before I had the data logging figured out so I didn't get the chance to examine what else might have happened in that same instant. I have an out of town job I'll need the truck for this weekend, I'll probably bring the device along and get some more data samples, see if I can catch that glitch again.

The ALDL cable can also apparently tell me what codes are set without waiting for them to blink thru, even while the engine is still running. The only stored code was a O2 LEAN condition which matches the momentary spike in the fuel trim.

 

[Ricko1966]

How old and what condition plugs,wires,cap,and rotor? A misfire will show lean,while it's misfiring. Spray under the hood with salt water out of a spray bottle at dark look for arcing. Someone's going to say a miss fire is rich because of tge unburned gas. But you have 14x as many O2 molecules as gas molecules,so the o2 and ecm see lean.

 

[YakkoWarner]

How old and what condition plugs,wires,cap,and rotor? A misfire will show lean,while it's misfiring. Spray under the hood with salt water out of a spray bottle at dark look for arcing. Someone's going to say a miss fire is rich because of tge unburned gas. But you have 14x as many O2 molecules as gas molecules,so the o2 and ecm see lean.

Plugs, rotor wires and cap are all less than a year old. Didn't think of a misfire being the cause of a lean spike, but now that you explain the logic it makes sense. Was playing with it well after dark last night trying to get the hang of the software and adjusting the TPS - didn't see any flashes or arcs but it was also dry. Will try the spray technique maybe tonite time permitting.

 

[gmbellew]

There is a lot to unpack with TBI. Hit up the reference library and download the emissions and drivability manual for your year. That manual, coupled with your cable and software, will be all you need to understand things that the ECM is doing.

But here is an overview.

Depending on your setup, you may be able to see sensor values that are in appropriate units, or you may just see voltage. Most of the sensor values make sense except TPS % never seem to be quite right for me. There are conversion tables in the manual for volts to units for the various sensors.

TPS is variable voltage based on throttle. Idle should be 0.5-0.9 volts. Wot should be 4+ volts.

MAP is manifold pressure in KPA. Subtract the number from atmospheric to get vacuum.

Knock counts is individual knock events. You should see some on start up and maybe a few every now and then ticking.

CTS is coolant temp at the thermostat sensor (not the sensor on the head between 1 and 3 that goes to the gauge).

BLM is long term fuel trim. 128 is perfect. But anywhere from 120 - 140 or so is ok. It might very rarely go outside that range for a short while.

INT is short term fuel trim. 125 is perfect and it is sort of a short term adjustment to BLM on the overall fueling. Example - if BLM is 128 and INT is 130, it is adding some fuel. If it stays adding, it will adjust the BLM.

IAC should be high on start up and decrease as CTS gets warm. At warm idle in park it should be 5-35. At warm cruise mine usually jumps to 80-100 and I don’t know how it picks this value. Then as you come to a stop, IAC drops to idle it down. If the ac kicks on, it adds 30 or 40 to the IAC to balance out the load.

No way to monitor EGR except when it fails self test it sets a code.

TCC lock is reported.

A thing I like to watch is “idle/off idle” mode. It should go off idle when you give it gas or are moving above a certain speed. Goes into idle as you stop.

Also keep an eye on loop status. It should be open when you start up, and go closed as the engine warms. The difference is closed loop uses O2 feedback to adjust fueling.

O2 sensor should be variable as engine warms and oscillate between .1 and .9 or so volts. .1 is lean and .9 is rich. It constantly adjusts fuel to try and keep it around 0.45.

There is a rich/lean command that I think is the opposite of what O2 reads. Low O2 commands adding fuel (rich command).

I also watch battery voltage, tach and speed on my Home Screen.

 

[gmbellew]

Is a slight varience (like 124 to 132) an acceptable range? I did see it go up significantly (like 145ish) for just a second and that -as expected- did trigger the SES light for a minute or 2 before it went back off. Unfortunately that was before I had the data logging figured out so I didn't get the chance to examine what else might have happened in that same instant. I have an out of town job I'll need the truck for this weekend, I'll probably bring the device along and get some more data samples, see if I can catch that glitch again.

The ALDL cable can also apparently tell me what codes are set without waiting for them to blink thru, even while the engine is still running. The only stored code was a O2 LEAN condition which matches the momentary spike in the fuel trim.

If the O2 sensor is going bad it will give bad data and cause odd fuel trims. If it isn’t regularly oscillating around, I’d suspect a bad one.

Earlier this summer I had a lean code and looked at the data and the O2 sensor would randomly get stuck high, then low, the oscillate normally for a while, etc. it would mess up the fuel trims and can cause drivability issues on a warm engine, particularly at low RPM where a little off on fueling can go a long way to causing a problem.

 

[YakkoWarner]

I've only had the cable/software working for a day so far so I'm sure theres a long learning curve ahead, but you already gave me some good clues. My IAC while driving was up around 145, and seems to immediately jump between 90-something to 140-something in unison with using the throttle. When I went back into PARK at the end of my short test ride, it stayed at 145 for a full minute before slowly clicking down to the upper 80's. It never goes under 85. Looking at the graph across the whole 7 minute test run it also never seemed to go over 145, but the ups and downs coorespond exactly with the rise and fall of the TPS except for the very end where it stayed at 145 for a long time with the TPS at 0.47 (I was aiming for between .45 and .5 for pedal full-up after adjustment, it had been at .7)

I have the manual downloaded, but never really dug too deep into it because I didn't have a way to read the necessary values from the ECM. Now that I have that working, the real work starts I guess.

 

[Fat 454]

What truck are you trying to get live data on. I just read your bio it says you have 73 c20 there is no on board diagnostics for 73. Earliest for GM I'm aware of is 1980. And I think that's only Cadillac Sevilles

Ha! - we have 3 Subs in various states of decay ( its a disease I tell ya! ). Trucks I am interested in are my son's 1991 OBS K2500 with a 350 / 700R4 and TBI, and my 1990 OBS 2wd TBI 350/ NP3500. Will post a build thread under "other vehicles" at some point.
The '73 Sub is a 454 with a carb and manual trans - closest thing it sees to a computer is my 'phone when I toss it in the console ...
Been looking to upgrade the 1990 with a 454 TBI, so I guess I will need a matching ECU and loom to run it ? Can you get a stand alone ECU, like those for the LS motors ??

 

[Ricko1966]

Ha! - we have 3 Subs in various states of decay ( its a disease I tell ya! ). Trucks I am interested in are my son's 1991 OBS K2500 with a 350 / 700R4 and TBI, and my 1990 OBS 2wd TBI 350/ NP3500. Will post a build thread under "other vehicles" at some point.
The '73 Sub is a 454 with a carb and manual trans - closest thing it sees to a computer is my 'phone when I toss it in the console ...
Been looking to upgrade the 1990 with a 454 TBI, so I guess I will need a matching ECU and loom to run it ? Can you get a stand alone ECU, like those for the LS motors ??

There is lots of standalone efi for these vehicles as a matter of fact @Matt69olds is trying to sell his he's upgraded to a system to control an electronic transmission too.

 

[YakkoWarner]

Ha! - we have 3 Subs in various states of decay ( its a disease I tell ya! ). Trucks I am interested in are my son's 1991 OBS K2500 with a 350 / 700R4 and TBI, and my 1990 OBS 2wd TBI 350/ NP3500. Will post a build thread under "other vehicles" at some point.
The '73 Sub is a 454 with a carb and manual trans - closest thing it sees to a computer is my 'phone when I toss it in the console ...
Been looking to upgrade the 1990 with a 454 TBI, so I guess I will need a matching ECU and loom to run it ? Can you get a stand alone ECU, like those for the LS motors ??

Most of the sensors will probably be the same for the 454 TBI (which is what I have) but they will likely be in different places making the wiring become more than a direct swap. The other, larger issue is the computer and its programming. The same physical computer is listed as being for all the different engine sizes and was used in a variety of trucks and cars, but the PROM chips (containing the actual software code that it runs) are absolutely tailored for each engine and vehicle type. If you can find the right PROM chips, extending the wiring to a sensor or 2 would probably be doable.

Get the ECU ID number off your existing computer (should be readable behind the glovebox) and then you can crossreference from there. When you buy a new ECU you do not get the PROMs, so finding those may be harder than going to a 3rd party system.

 

[Fat 454]

Most of the sensors will probably be the same for the 454 TBI (which is what I have) but they will likely be in different places making the wiring become more than a direct swap. The other, larger issue is the computer and its programming. The same physical computer is listed as being for all the different engine sizes and was used in a variety of trucks and cars, but the PROM chips (containing the actual software code that it runs) are absolutely tailored for each engine and vehicle type. If you can find the right PROM chips, extending the wiring to a sensor or 2 would probably be doable.

Cool - thanks - sounds like I will start with the PROM availability then, as all the hardware is easier to source. Thanks for the warning ..

 

[Ricko1966]

Cool - thanks - sounds like I will start with the PROM availability then, as all the hardware is easier to source. Thanks for the warning ..

I think @Mr Clean may have some of what you need. I think he had ac454bthrottle body assembly,don't know what rlse. Heck I may have the ECU and prom,he sold me one I asked no questions about application. Let's see if he chips in as to what he has and what I bought I never even unboxed it. It was just spare parts.

 

[Sgt Gus]

Great thread, and perfect timing.
Key for me is to pick my head up from the laptop and remembering what my goals are, and what I CAN do with the information.
1) Is everything working mechanicly and then sensors.
2) If I do have mods, am I close enough to stock, or purchase a moded chip, or have someone burn a custom chip...
3) Alternatives to burning a chip...

 

[chris3353]

Yes I did - and was even able to take the whole setup for a litlle trip thru the side roads last night. Then realized I had no idea how to actually log data with the software, spent a good 30 minutes sitting in the driveway fiddling with it and then took ANOTHER little ride down the side roads to actually get a data stream sample.

The Moates cable works really good - I am less convinced I have the correct definition files for the software since the coolant temp reading reported by the software is backwards (software says almost 200 degrees C on inital startup and comes down as the truck warms up). I don't think my sensor is bad because the truck wouldn't run right at all with the sensor that badly out of whack, I fully expect its just the software mis-interpolating what the computer reports.

Other values seem to all be in believable ranges even though the units reported don't always make sense (short term fuel trim starts as "128" but we don't know what its 128 of, MAP sensor is reported as voltage but without any indication of what the expected low and high values should be, that doesn't really help).

Oddly enough, spark control isn't something that the ALDL data seems to be able to report, even though the computer is controlling it internally. It does not show up as a monitorable/loggable value (unless again, I could have incorrect config files for the software).

It does report IAC counts and TPS voltage which already is helpful - I was able to readjust my TPS sensor to be at .47 with pedal fully up vs. the .69 it was when I first connected the scan cable. After my 7-8 minute ride through the neighborhood, I already starting seeing trends that I don't understand in the relationship between the IAC, TPS. The IAC really seems to want the idle to be around 950, when you shift into reverse or drive the idle momentarily drops, but then the IAC counts start clicking up until again its at around 950-975. Likewise when you shift back into park, the engine RPM surges up to around 1700 and stays there for right around 60 seconds before the IAC counts start clicking down, again settling around 950-975 RPM. The weird thing is, while driving the IAC counts closely mirror the TPS voltage with almost instant response up and down. I didn't think the IAC was supposed to operate in unison with the TPS, but maybe it does. I know nothing about how all this is supposed to work. The goal is to record, learn what is and isn't right and then make right what is wrong.

You got Windows 10 to talk to the OBD1? I can not get WindALDL to communicate using windows 10

 

[chris3353]

Yakko,

I chased high idle for a while. It ended up being a faulty TPS. The TPS tested perfect. The truck would idle nice and then back to being high. I could never find it.

One day, sitting at a red light, (data log drive) i catch a blip out of the corner of my eye. The TPS jumped and i was not touching the gas. After this, noticed, once it happened there was no recovery until i cycled the key. replace TPS and solved it.

Your first step is making sure the truck is in Closed loop and stays there. A heated o2 sensor is needed. The exhaust is barely hot enough to keep a single wire 02 closed in the stock location.
if your O2 in in a header collector, it needs heat.

Chris