"Surging" while in gear + NOT applying throttle

[ILoveMPower]

When I'm in 3rd gear say, and I bring it up to about 3.5-4k, and then let off to have the compression slow me on down... I can feel the car "surging" so to speak. It feels like you are wiggling your foot slightly on and off the throttle over and over very quickly. I can tell throttle is being applied somehow because the economy guage fluctuates WITH the surging.

any ideas?

[BillionPa]

not the typical vacuum leak since the air is being metered. ICV actuator possibly toast and not keeping it shut with the additional force of the high rpm vacuum.

could also be a bad MAF. is your idle iffy?

[wingman]

Is a vacuum leak confusing the computer?

[Morgenster]

What particular sensor shuts down fuel supply and tells the computer that you're coasting? I'm imagining it must be something that registers the inverse torque when the wheels start pushing the engine instead of the other way round. I'm also thinking that your engine might think it's dropping to idle way to soon and gets confused right there opening the icv.

[jbourke]

What particular sensor shuts down fuel supply and tells the computer that you're coasting? I'm imagining it must be something that registers the inverse torque when the wheels start pushing the engine instead of the other way round. I'm also thinking that your engine might think it's dropping to idle way to soon and gets confused right there opening the icv.

Speed sensor + throttle (idle) switch tell DME your car is coasting.

[DanDombrowski]

I had a similar problem when I had just bought my car, where if I left it in 1st gear and idled without the gas on it would buck at times.

When I first got the car though, I replaced a broken cruise control vacuum line, cleaned the TB, replaced the air filter, ran some fuel injector cleaner, and replaced the spark plugs. After all that, I didn't have the problem anymore.

I can't tell you which one of those fixed it, but my guess would be either the CC vacuum line or cleaning the TB.

[ILoveMPower]

I have never noticed it in any other gear besides 3rd, and its not like violent, the economy guage never drops below like 40mpg, so its very slight

Could a slight rip in my intake boot cause this? I might have to do a close inspection

[ILoveMPower]

not the typical vacuum leak since the air is being metered. ICV actuator possibly toast and not keeping it shut with the additional force of the high rpm vacuum.

could also be a bad MAF. is your idle iffy?

It idles like a champ, but quick punches of throttle from idle is a bit rough

[Morgenster]

I have never noticed it in any other gear besides 3rd, and its not like violent, the economy guage never drops below like 40mpg, so its very slight

Could a slight rip in my intake boot cause this? I might have to do a close inspection

Wait a sec. Are you saying the gauge never goes all the way to the left?

[BillionPa]

throttle position sensor perhaps....

[ILoveMPower]

Wait a sec. Are you saying the gauge never goes all the way to the left?

Yes it does, but when I feel the surging, it drops down a bit, never lower then 40

[Morgenster]

Yes it does, but when I feel the surging, it drops down a bit, never lower then 40

That would mean that the injectors and fuel pump are actuated at that precise time. So I think you should check all sensors responsible for telling your computer when your car is compression braking. TPS, RPM sensor, MAF. Or maybe ICV partially obstructed.