Throttle Blip Followed By Shudder

[Wacky Dee]

I've noticed that if say the car is idling and I blip the throttle (say to 2-3rpm) for just a second and let go .. as the rpm drops down to 700-750 (normal idle) it shudders for a second.

I never knew what that was but with consult connected and watching the various sensors ..I noticed after the blip, the timing falls down to 0 as rpm reduces to 750 and then quickly goes back to 5deg or whatever and this is where it shudders/shakes..between the 0 and 5 (normal) idle timing.

What could this be a sign of ? Coilpack issues ? Ingition related ? Bad timing map/tune ?

[TiTAN]

stock ecu? have you cleaned your idle air bypass? mine used to do that once it was up to operating temperature stopped after i cleaned it out.

[Wacky Dee]

you mean the aac valve? I was gonna clean it ..opened it up and noticed it looked as new inside so left it.

[lachlanw]

search power fc disease . end of story .

hint

watch your airflow meter voltage after you let off the gas

[Wacky Dee]

I don't have a pfc .. stock ecu with daughterboard (remapped) I'll keep an eye on the maf voltage .. what should it be ? could it be a problem with the maf wiring ?

[T04GTR]

if its not stock then thats your issue.

[Wacky Dee]

the guy that tuned it (Toshi) has done a lot of skyline for sau members ... what are you saying that he doesn't know what he's doing and ignition timing is not right or what?

[Dorifta]

can be many things, usually associated with atmo venting bovs

[Wacky Dee]

stock bov..could it have anything to do with a slightly dodgy wastegate or actuator ??

[lachlanw]

i didnt ask if you have a power fc . it makes no difference . it is called power fc disease .

it is air going backwards through your airflow meter . ecu doesnt know which way the air is going so it thinks its going in . air in =fuel in . but the air never went in so car runs rich and tries to burn it all . your lucky . somepeoples cars do it so bad the car stalls

[Wacky Dee]

Ok I've never heard of the term "pfc disease" and I've been into this stuff for 2 years now.. Not even google brings up anything on "powerfc disease". So if it's a term you came up with, congrats. But it might be more helpful to actually explain what you mean to begin with than be fancy and make up stupid phrases that have no meaning whatsoever.

Why would the air be going the wrong way ? Is this something that can be fixed/adjusted or is it normal ? Please no more disease talk.

[lachlanw]

oh well ive seen plenty about it . including 2 seperate multi page articles in australian car magazines that live in the bog . they seemed to recon it was common and well known . the air goes back wards because the turbo has sucked in more than the engine needed and then youv shut the throttle so it has no where to go but back out .

[Wacky Dee]

isn't that extra air supposed to go out the wastegate or be recirculated back into the intake ?