A little hesitation around 2000RPM after a long FAS

[RobertSmalls]

Now that it's getting colder, I have a repeatable symptom as a result of my FAS button. Upon restarting the engine after a >1min engine off, especially when the engine is still cold, I get hesitation (major lack of power) for 1-3s around 2000RPM in 2nd gear.

I'm not worried about it, since I'm pretty sure it's just the ECU misjudging how much well the fuel will atomize, and it corrects itself within a few seconds. I just thought I'd share. Does anyone else have the same issue? Or does anyone else FAS for a minute or two with a cold engine and sub-freezing ambient temps and get no hesitation?

[MN Driver]

Not sure if this is the problem or not but I had a similar issue after filling up at the gas station, whenever the engine was cold it would stutter a little, I'd watch the ignition timing drop back in the scangauge and then it would act normal again later on. The next tank of gas and things were normal. If you have a recently filled tank, it could be that. If not, likely something else. I wasn't FASing much then though but the RPM it was being finnicky at was about the same.

[elperepat]

I get the exact same issue: lost of power on acceleration after FAS. Nothing dangerous, but a bit surprising at first. Now that I know it can happen, I use full assist to reduce the deceleration during the 1 to 2 seconds it lasts.

[RobertSmalls]

Originally Posted by elperepat

I get the exact same issue: lost of power on acceleration after FAS. Nothing dangerous, but a bit surprising at first. Now that I know it can happen, I use full assist to reduce the deceleration during the 1 to 2 seconds it lasts.

On my new commute, I can predict when it's going to happen. Rather than subject my emissions systems to this hesitation (which passes unignited air and fuel straight out the exhaust valves, right?), I upshift just before reaching 2000RPM, so the hesitation doesn't happen. Then I apply assist as traffic requires.

[3-Wheeler]

Robert,

I think the intake resonator circuit is also messing with your situation at 2000 rpm.

Several years back I did a "resonator test" right after installing my hot air mod to see if the resonator actually helped the engine at low rpm's (see below).

How to Build a Hot Air Intake

What I found out is that, yes, the intake resonator does help boost power at 1200 rpm's and above until the null at what else... 2000 rpm.

And above this rpm, at about 2300 rpm's or so, again the resonator helps out.

I do like you do, and short shift typically just before 2000 rpm's or so.

Jim.