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Hot start idle problems


Matmor
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Hi,

I have a V5 possum link and I'm having problems making the car idle correctly a minute or so after a hot start.

After bliping the thottle or revving the engine the rpms fall to well below 800rpm and seems to have trouble rising again (rpms rise very slowly).

A minute or so after starting the engine this problem goes away and the car idles perfectly. What could this be, and is there a way to resolve it?

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This could be a heat soak issue where the engine intake is getting very hot when the engine sits and then after it has run for a while air flow has cooled the intake???  This is usually what IAT correction is used for.  You might be better to tune the lower RPM/load zones to get the engine to come back up to idle.  You may need some more advance at low RPM to help increase engine speed.

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The problem i described is when the car is stationary so there should be no air flow at all to cool the intake..

What is IAT?

Also it seems to be impossible to get an AFR in the region of 14.5:1. Either it is 13.8-is or 16-ish. I've played around with the voltage correction, clamp etc and trying to adjust the fuelzones to get an AFR in the fourteens, but it seems to be impossible. Whenever I try to get the AFR above 14.0 the kpa rises and the AFR klimbs to 16-17...

Is there a hidden function like COLD but for hot starts that adjust values for one minute or a minute and a half?

All this is when running the link on open loop lamba.

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The air flow I am speaking of is inside the intake...  IAT means Intake Air Temperature correction.  IAT Correction is used to adjust the fuel delivery for intake temperature.  This would provide the compensation for hot restarts.  Unfortuneately older ECU's like the V5 range do not have this function.  When an engine sits, the intake temperature can get up to about 80 deg C also the fuel temperature gets very hot.  After starting it takes some time for the intake and fuel temps to come back down to the temperature at which the engine was tuned.  It is quite common to run an AFR of 13.8 - 14.3 at idle to keep a stable idle.  When you lean the engine up and the vacuum (kPa) changes and it goes lean, this is because you have moved into a different zone.  You must also adjust that zone too.

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