Hey everyone,

So, I have tried everything on this truck before getting a cable, and now I have logs of this stubborn thing refusing to work. Im new to the logging and not REALLY sure what I am looking at and would love some other folks to look at this with me.

Fresh tune up, IAC, New map sensor, TPS, temp sensor, and vacuum leaks have been checked and fixed. I have a second complete throttle body with brand new injectors that hasnt given me any better results. Im not having any luck at all.

During these logs you can see me attempting to adjust the idle speed. All tests were at 0% throttle. To simplify the diagnostic I wanted to keep it in closed loop so during one test I unplugged the O2 sensor. The software reported the TPS at 15% so I attempted plugging in the new TPS without installing it, where it began reporting a negative 12%. You can see this in the log. My final test was to use a different ECU.

My goal is to get the truck running well enough to give it to my sister. I have access to a Moats Burn 1 but I have never fussed with custom chips yet. I would love any input you have.

Link to Log files hosted on GitHub.

If you are not used to downloading things from Github, here is a photo showing how to download it. Click "Clone or Download", as shown in the photo, then "Download as zip"

EDIT: Links didnt work.

 

Your log files are password protected.

RBob.

 

Rob, thank you! For now I uploaded the logs to Github, which should work ok unless you have another suggestion?

 

WHAT YEAR VEHICLE? WHAT MODEL?

What does a "tune up" include?
Did you set the timing? Did you pop the one-wire timing connector, and then re-connect it after achieving "0" on the base (initial) timing?
WHICH "temp sensor"? The one for the gauge, or the one for the computer?
HOW did you verify there are no vacuum leaks? Do you have the CORRECT TBI base gasket? There's at least two designs for the 5.7L. There's other designs for the 7.4L. Is it in good condition?
HOW are you "attempting to adjust the idle speed"? Please tell me you're NOT screwing with the tamper-protected base idle (throttle position) screw.

Unplugging the O2 sensor will PREVENT closed-loop operation. You're guaranteed to be in OPEN-loop.

Have you checked for throttle cable binding? Is the Cruise Control or Trans TV cable too tight? (Disconnect the cables one at a time to see if they're holding the throttle open.) I had a friend working in the service department of a dealership, that got assigned to a vehicle that wouldn't idle below 2K or 3K RPM. He lifts the hood, and there's a can of Dinty Moore beef stew warming up on the intake manifold, jamming the throttle open.

Have you adjusted the TPS?

What does the computer think the coolant temperature is?

What is the commanded idle speed vs. the actual idle speed? Does the IAC work?

(I don't download "logs". I'm looking for you to post the answers.)

 

1990 k2500
Tune up was cap, rotor, and plugs. Check the wires with an ohms gauge.

Yes I set the timing with the wire disconnected then reconnected it.
Rebuilt the TBI, it came with two gaskets for the base of the TBI and I used the one that looked correct, the other would definitely have been a vacuum leak.
Verified there are no vacuum leaks using a can of starting fluid and a straw to spray all around the intake manifold and base of the TBI. This lead to replacing the intake manifold gasket and the EGR valve.

The tamper proof screw had already been tampered with when the truck was purchased. So yes, sadly, that is what I'm adjuadjusting.

I wish it was that simple, but sadly it is moving freely.

The TPS seems to have very limited adjustment, and it's has not made a change. I even tried plugging in the new TPS before installing to see if that changed the behavior at all. There didn't seem to be a correlation.

Coolant temp according to the computer matched up pretty closely to my laser thermometer, but I don't think it ever got above 100 degrees during this round of testing.

i looked for a commanded idle speed and couldn't find it with this ADX loaded. I'm not sure.

The IAC is new and does work.

I had beaten my head against this engine and decided it wasn't worth much more effort and I should replace it with a cheap ”known” 350 from another TBI 350 truck. I wasn't sure if someone who understood the data a little better could look over it and see something obviously wrong.

​​​​​So much time and money spent on an engine that doesn't have great compression to begin with, I might just start the engine swap this weekend. =\