Thread: Stepper Motor functionality?

May I ask:

Does the Plenum stepper motor on a 14CUX EFI setup close (ie. reduce the air flow) the warmer the engine is (based on coolant temp?).

Alternatively, if this is BS... how does it work?

Reason for asking.. I am planning to fit an after market ECU that uses CLT temp to control the stepper... and I'm curious to know how the std setup works.

Originally Posted by linzerl

Many thanks.. yes.. you guessed correctly.. going Megasquirt..

So why does the stepper work like that.. with a manual choke, air flow is restricted.. meaning less air and a richer mixture... yet with the stepper open on the 14CUX.. there is more air which is reduced as coolant temp increases.?

Manual choke includes a fast idle cam. In an EFI the stepper does the job of a fast idle cam, the ECU does the richening. So the temp sensor tells the ECU how warm, the programming says how fast to idle, ECU controls the stepper to achieve that idle speed. Not exactly one-on-one but its more flexible. As the idle speed varies the MAF/ECU will control the mixture so there's no leaning out with higher idle speed.