tritonium

I am dropping idle randomly to 600rpm once car heats up -I will be cleaning out the IAC this evening and checking the vac lines - any way to point me in a direction before i go crazy due to my ignorance

Thank you in advance

TTS Data Master logged these

http://www.2shared.com/file/GVCynzyt/MurphyLogTwo.html

Have a Nice Day

Brad

tritonium

Update :
After further forum reading Injuneer posted if the IAC count climbs up tot 160 and nothing happens the IAC motor / idle air passage under the TB is most likely the problem - replacing the IAC

johnnyb

umm... does datamaster not work with 93s? I didnt think it did and for your sake lets hope not... that log is wayyyy messed up!

tritonium

you are the 2nd person to tell me that - I am unsure why.... It displays fine for me as well as my tuner.

Are you using Datamaster DA ( not sure if it matters what program to playback i know DA records 93s)

Thanks anyway - it is running well.

bobdec

Brad, correct, you need Datamaster DA to view the '93 playback, download is free, license lasts forever if used for viewing only (no logging). I was looking at your log , but since the post was so old I did not reply. What was the original problem ? During idle at the end of the trace in closed loop I saw your O2's looking like a square wave locking at 800+ mv for 8-10 seconds then locking at below 100 mv for 8-10 seconds and repeating the process as the RPM varied from 800-1200 RPM and the IAC jumping from 36 to 160 during the lean (100 mv) O2 readings. ST BLM's were at 200+ when the O2's went to 100 mv. What the heck was wrong ?? Just curious on what would have caused this, was it caused by the tune ?. Never saw an engine behave like that at idle..

tritonium

I believe the IAC was busted - will let u know when the new IAC is replaced.

Injuneer

I was using the EE version to read the file, and it didn't index correctly. I just downloaded DataMaster DA version, and the file looks OK. Apparently, you have to use the same version to view the file as was used to record it, as noted in a post above.

Looks like the problem pops up around record #10000. IAC goes up to 160, O2mV's drop to less than 100, STFT's go sky high and drive the LTFT's up to 158 on the left side, less on the right side, but it looks like there is a bit of a split BLM problem. I'll take a longer look tomorrow.

tritonium

Thank you both for looking at the log ! - I really appreciate it. Once I get the new IAC in I will post another log to see if everything is in range. I am sorry but what is STFT and LTFT //// and what is split BLM.


I am sorry about the noobness to this reply - This is the newest and final step to the rebuild. lol final step to a car.

Thanks again - will post once I have a new log.

Injuneer

STFT = short term fuel trim, aka "integrators". These are corrections that the PCM temporarily makes to the injector pulse width calculation, to allow the A/F ratio to swing back and forth from slight lean to slightly rich (compared to 14.7:1 stoichiometric ratio). That is required for the cats to work. If the PCM is calculating the A/F ratio correctly, and all the parts are working like they are supposed to, the STFT's will average 128.

When the PCM sees that the O2 sensor readings are forcing the STFT's to deviate on average above or below 128, it adjusts the LTFT's = long term fuel corrections (aka block learn multipliers, or "BLM") in the same direction. These are "permanent" corrections, and this it what the PCM "learns" with regard to A/F ratio control, and store in volatile memory. For the LT1, there are 18 pairs (left and right bank) of corrections, corresponding to a grid of RPM on one axis and engine load (MAP or manifold absolute pressure) on the other axis. These are called cells, and range from Cell 01 for low RPM/low load, to Cell 15 for high RPM/high load, plus Cell 16 for idle, Cell 17 for decel and Cell 18 for open loop load and some PE (power enrichement) mode conditions.

You can get a bit more info on your scan data in my online scanner guide:

http://www.injuneer.com/ScanMast.html