Recent content by 2006Tahoe2WD

  1. 2

    Long term and short term fuel trims intake leak, low idle, improving fuel mileage. Mpg

    I'm curious to see if your LTFTs change. I'm running +2-4% at idle and ~+10% on the highway. I'm thinking the injectors are not flowing enough and the "+" values are caused by the ECU trying to get more fuel.
  2. 2

    My current fuel trims - idle, 2000rpm, 3000rpm all no load

    After the tank with 100 Oct, I did not see much change (LTFTs) at cruise speed. I did see a bit of improvement at idle. Idle now running +2-4%. Thinking on this a bit more and my current guess is the injectors are somewhat dirty or at least not putting out what they should. E.g. at low flow...
  3. 2

    My current fuel trims - idle, 2000rpm, 3000rpm all no load

    Yesterday (Thursday) I bought 10 gallons of 100 Oct gas at the 76 station here. $10/gallon. This was mixed with about 4 gallons of 87 Oct. The fuel trims lowered a bit but at steady-state highway the LTs are about the same. The 100 Oct might also I have ethanol, this is unknown. I'm still...
  4. 2

    My current fuel trims - idle, 2000rpm, 3000rpm all no load

    Yesterday I tried displaying the Commanded Evaporative Purge and couldn't get it to work. That is a standard listed PID but for some reason it is not listed in OBDLink. So my experiment to compare trims to the purge air amount isn't going to happen right now.
  5. 2

    My current fuel trims - idle, 2000rpm, 3000rpm all no load

    I've watched the LT and ST going up a steady incline recently and both seem to behave themselves - no big moves. When running on the flat I try to hold the pedal steady and watch the airflow in g/s and see if I can make it also steady then watch the trims and see what is going on. As I...
  6. 2

    My current fuel trims - idle, 2000rpm, 3000rpm all no load

    An additional thought.... You read on the internet that the STFT and LTFT are added to get the actual trim that will be applied. Yes and no. My STFTs bounce up and down rapidly about +/- 2% -> +/-3%. Let's call it a 6% swing. I don't think the ecu would swing the fuel delivery 6% every...
  7. 2

    My current fuel trims - idle, 2000rpm, 3000rpm all no load

    I have an idea to potentially relate LTFTs to EVAP flow. I added the commanded purge value to my "dashboard" on my MX+. Haven't tried it yet. I'm low on gas now and will soon buy the 100 octane 76 gas in hopes it is non-ethanol. Could be about $6/gal.
  8. 2

    My current fuel trims - idle, 2000rpm, 3000rpm all no load

    In upper right corner "08/05". I guess that's the mfg date. I could not pull up an OS name using MX+ and OBDLink. It might be there but I couldn't find it.
  9. 2

    My current fuel trims - idle, 2000rpm, 3000rpm all no load

    Thanks very much for this. I think you must be correct that different models (e.g. flex vs non flex) have different PIDs that show up or respond. Please stand by I'll check to see if my OBDLink software will show the OS name. Yesterday I went to the 76 Station that is supposed to have...
  10. 2

    My current fuel trims - idle, 2000rpm, 3000rpm all no load

    I'm very interested if you are seeing or are able to pull up the PID for ethanol percentage. I would guess since you are flex fuel that PID should be available. All my attempts to get an ethanol percentage have failed. I think we both have the J1850 VPW protocol, which is the "old" slow type.
  11. 2

    My current fuel trims - idle, 2000rpm, 3000rpm all no load

    After more digging the PID hex is 52 (dec 82) for Ethanol Fuel %. Still not sure if that can be pulled via the OBD port on my car. I contacted OBD Link MX+ people and they responded that if I don't see it under the SAE PID list then it is not available on my Tahoe.
  12. 2

    My current fuel trims - idle, 2000rpm, 3000rpm all no load

    This adds to the thinking that the base map doesn't not assume there is any ethanol in the gas. Therefore, when 10% ethanol is encountered the O2 sensors tell the ECU to run rich and the injectors get more on time. No real harm done, just some LTFTs that run a bit high. This brings up the...
  13. 2

    My current fuel trims - idle, 2000rpm, 3000rpm all no load

    All the J1850 VPW PID lists I could find don't contain ethanol percentage. I'm claiming no scanner can read it. It might be there but no way to read it.
  14. 2

    My current fuel trims - idle, 2000rpm, 3000rpm all no load

    Confirmed my 2006 Tahoe has the J1850 VPW protocol. Pins 2, 4, 5, 16 are connected. What PID limits this means - I don't know. More googling required.
  15. 2

    My current fuel trims - idle, 2000rpm, 3000rpm all no load

    Wiki has this.... so a question might be can you even read the ethanol percent using J1850. What model year GM Tahoe/Silverado/etc. provides which protocols? 2008: All cars sold in the United States are required to use the ISO 15765-4[9] signaling standard (a variant of the Controller Area...
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