Idle pb with AEM engine management system

[Cyruss]

Hi everyone.

Since a few days I have a idle pb on my GTS 97 Viper. I have AEM EMS. My idle was perfect but a little bit too high (900 minimum), I start to modify the tune (I made it myself a few month before) and I suceed to lower it to 750rpm (I got cam, heads, 725cc injector, fuel rail ....). But sometime even cold or hot the idle goes between 1500 and 1700rpm .... up and down ... If I continu to drive the pb stop by itself and come back randomly ...

The only thing I modify to lower the tune was idle% vs idle target, ignition map, fuel map and ... Idle PW frequency (31hz instead of 15Hz).

so now I have a lower idle but unstable

As sometime it's work and sometime not, it may be the idle valve itself ? but it's weird that the valve dead as the same time as I change some parameter in the tune ...


Thanks for you help ....

Here is the screenshot of the idle parameter on the AEM. the Idle% vs idle RPM is perfect, no correction at all between 800 and 1500rpm at normal condition - when it's work

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[DrumrBoy]

This may sound stupid, but depending on the vintage AEM you're using you may have to wait until the car gets up to temp, pull over and shut it off, then turn the key to "on" without starting, leave it there for 10 seconds and then start it. For some reason idle is unstable until you do this on some AEMs. Its completely ridiculous I know, but give it a try and see if it addresses your idle stability issue. (there's a gas station about 3 miles from my house where I always pull in and perform the procedure......they think I'm taunting them or something because I seldom buy gas, though I always stop and start......)

 

[eckeph]

From the AEM 30-1500 EMS manual:
The Viper idle air control motor is sometimes susceptible to drift and/or sticking. If your idle control hangs abnormally high or low during operation, turn the key to the ON position and wait approximately 10 seconds before starting. The EMS will reset the idle motor and store the new position references.

 

[DrumrBoy]

Its truly an amazing coincidence that the idle air control drifts or sticks EVERY time one starts the car yet never sticks after you do the 10 second drill? I'm sure it has nothing to do with the AEM.....

 

[DrumrBoy]

Anyhow, Cyruss did it so,ve the problem you were having?