My first problem... rev bounce
10-27-2015, 11:36 PM
#1
My first problem... rev bounce
I've only driven the car once for a short distance since I installed the CAI and headers. Tonight I was going to drive it to the store. The first time I drove it the idle was perfect. When I cranked it up tonight the tach went to 1200. And then it started bouncing between 1200 and ~2000 alternating w/ a 1000 to 2000 bounce. Steady bounce... never resting at either point.
I figure it has something to do with the recent new parts.
Maybe the Bosch O2 sensors I was warned about? But I think I read a post here about a similar problem that was caused by some type of valve inside the intake manifold or the part that controls that valve. I haven't found that thread again and don't recall the part name. An acronym was used. IACV or something like that but not the idle air control valve. The actuator or controller is located on the back side of the IM and has a cable like a throttle cable. I unplugged the electrical plug and loosened the bracket to get more room to get to the exhaust manifold nuts. I was careful handling it and when I reattached the bracket and plugged the electrical connector back in it looked just the way it did before I toughed it. So I'm leaning towards the Bosch sensors.
Any thoughts on this?
I figure it has something to do with the recent new parts.
Maybe the Bosch O2 sensors I was warned about? But I think I read a post here about a similar problem that was caused by some type of valve inside the intake manifold or the part that controls that valve. I haven't found that thread again and don't recall the part name. An acronym was used. IACV or something like that but not the idle air control valve. The actuator or controller is located on the back side of the IM and has a cable like a throttle cable. I unplugged the electrical plug and loosened the bracket to get more room to get to the exhaust manifold nuts. I was careful handling it and when I reattached the bracket and plugged the electrical connector back in it looked just the way it did before I toughed it. So I'm leaning towards the Bosch sensors.
Any thoughts on this?
10-28-2015, 01:25 AM
#2
Drifting
Well if the car was fine before the mods then it must be something you did during the mods. Most likely the CAI... vacuum leak or vacuum hose left unpluged.
^ Are you talking about the idle srcew?
^ Are you talking about the idle srcew?
10-28-2015, 03:39 AM
#3
I've never looked for it but I'm pretty sure the idle speed screw is on the TB. It definitely wouldn't get in the way of exhaust manifold nuts. This isn't an idle surge, the tach needle is bouncing back and forth continuously between 1200 and 2200. No creeping or surging... straight up to 2200 and then straight down to 1200 like a metronome.
This is the part I'm talking about. It's called a bypass valve actuator but I haven't found out what it does.
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mike88se (10-28-2015)
10-28-2015, 04:09 AM
#5
Yes I was just reading about the Intake Manifold Runner Control. I suppose I'll cross that off the list of possibilities. I was leaning towards those new o2 sensors but I've never seen a bad o2 sensor cause something like this. Matter of fact I've never even seen a car do something like this. Its like bouncing off a 2200 rpm rev limiter.
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