Barometric Pressure

[Lexcelsior007]

Hi,

Does anyone know if/how the 1998 LS400 measures barometric pressure? Is it from the MAF or the ECU? My scan tool is showing a pressure of 22 (fluctuating) psi = 45 inHg. My GS350 shows a steady 14.6 psi = 29.72 inHg. The GS is correct for where I am (Hayward, CA). My MAF reading at idle is around 5 g/s and fluctuating which seems on the low side. My LS has been running extremely rich on both banks giving misfire and rich codes. Due to this I have surging rpms, hesitation, stalling etc. I know the ECU controls the fuel delivery based on altitude and since it thinks the air density is greater due to the higher pressure, it adds more fuel than needed. Am right in my thinking?

Anyone have any ideas? It would be useful if anyone can list their Barometric Pressure reading for comparison.

FYI, the ECU caps have been changed and MAF has been replaced without any difference observed. 

[pj8708]

Hi Neil,

This is a new one! I would suggest going to the Toyota tech site, TIS.com. The site has very in depth tech information for Toyota, Lexus, and Scion. There are schematics, text, and pictures for every component. The charge is $15.00 for 48 hours of use.

Let us know if you solve your question.

Paul

[Lexcelsior007]

Thanks, I will look into that next week. It would be great if someone has a scantool and can read their barometric pressure of their LS400 and post back. Mine seems to be slowly going up and down from 15psi to 25.2psi. Should be 14.7psi. I'm not getting any related code apart from PO172, PO175 and PO300 which are rich codes and random misfire codes. I am not sure what is causing it. I have checked the MAF wires, changed MAF, changed whole ECU with no luck. Also I hear a high pitched buzzing sound coming from the Throttle Control Motor when KOEO. Don't know if this is normal and/or related.