I got everything tuned in on my mega-squirt in the car however sometimes the idle is a bit funky. Anyone where have any mega-squirt experience they would like to shed light on?

When im idling it idles @ about 1000-1100 (b/c i have an after market high lift low duration cam) however after driving on the interstate for awhile it idles a bit higher around 1300-1400. So this requires me to constantly set the idle duty cycle which can be annoying. Anyone else having this same problem? I'm running a fast idle solenoid @ warm up so it idles higher at the beginning and as coolant temp increases the idle drops and idles fine when standing. Help anyone?

 

What conclusions can you draw about engine differences after driving on the interstate versus just driving around town? Any differences in coolant temp, underhood heatsoak (intake air temp), etc., that would affect the idle regulation? There are usually differences, you just have to figure out what they are. I don't know much about the Megasquirt software or what their engine management strategy is, but I work for an ECU company so there are fundamental concepts that are usually the same.

The only reason that I can think of for the fast idle is that the coolant temp is lower from the higher airflow around the engine (not just through the radiator) but that should stabilize very quickly as soon as you came down to normal street speeds for any length of time.

It's also possible that the short term fuel trim (or some other short term parameter) is getting thrown off by the interstate driving, but like I said, it's very hard to predict without knowing their engine management strategy. That would really surprise me if that was an issue, and I figure that the Megasquirt stuff is probably too sophisticated to have problems like that.

 

david warm the engine up then unplug the idle valve and adjust the set screw on the throttle body so that the engine is barely running. then lock down the screw and plug the idle valve back in you may need to adjust the dwel for pwm when warm