Hot idle/lean dies???

[ducman82]

Car starts and runs great during the day. but once hot and sitting, like when i am getting the kiddo from school, she leans out a dies. then seems to ru n lean for a good while before evening out...... SOOO odd! anyone see anything that pops out to them?

i can adjust Idle VE , but then idle can be really rich later.....

[slow_hemi6]

I would say your MAT sensor is heat soaking and showing closer to engine temperature, than the air temperature the engine is actually using. Hot air is thin air and ms compensates by pulling fuel as per the MAT air density table. If the sensor reads hotter than the actual air the engine is getting then it pulls too much fuel.
Looking at your log I would also question the amount of ASE % you are using at higher temps, especially as you have a long taper. There is a setting to ignore MAT during ASE and that can help get past heat soak with a long taper but only a little extra fuel or none at normal operating temps.

[ducman82]

Thank you.

ya my ASE taper was more a maxed out line! lol, i added some curve to it. i will look in to the MAT sensor, that does make some sense. it it located in the sock air box location that Porsche used in the 928 for their MAT.

[slow_hemi6]

Log was showing 144f / 62c for MAT which is quite a hot/undesirable intake air temp anyway, if it is correct.

[ducman82]

928's engine bay radiates and traps heat like no tomorrow. driving temps are fine. its just sitting/off this happens.

ill try shielding the sensor some. its mounted but the throttle body, in the air box, which is plastic.

[slow_hemi6]

Small block A body mopars with TBI's are bad for it too. I had no choice but to fudge the MAT correction table on mine. I have a flat 93% for 45c and above. Not a great idea for a boosted engine that can actually see high inlet air temps though.

[ducman82]

ya, my correction table had nothing. all 0's.

time to get it warm today and check it out.

[jsdevel]

Could it be a bad check valve? If it's getting that hot I suppose you could be losing pressure if the gas is vaporizing inside the line.

[ducman82]

ya know, i thought about that as well. but changing the MAT air density table seems to have made a difference.

i just am not sure about the MAT correction table.... how to adjust that correctly

[slow_hemi6]

Use the standard curve values up to about 10c past your higghest ambient air temp. Air temp here can get up to 35 degrees so I start to change the curve around 45c. It is easiest to let iat get to 45 then adjust the correction to give you your normal afr. Then just use that value for the higher temperature points.

[slow_hemi6]

Something like this, for example.

MAT.jpg

[ducman82]

this is what i set up yesterday. seems to work ok.

[ducman82]

why is it reading higher than it actually is? i swear it USED to show it spot on.

[slow_hemi6]

Not 100% sure but I think the clue is that the gauge is Estimated Intake Air Temp. Have you been using/changing MAT/CLT Correction table? Standard it is all 0's.

[ducman82]

a little. but i just re zeroed it

[TurboFan]

IAT correction method and ASE playing will not work for engines with big heat soak for example from turbo. Main problem in after start is fuel injectors got heat and vaporized so actuel fuel PW isn't really the same. We need ASE correction based not only on CLT but also must be blending with IAT to add some extra fuel in after start idle period and disabling this additon after moving off when more fuel comes to injectors to cool down them and giving PW as expected.