When I accelerate hard (pedal to floor), the car takes off like a rocket once the RPMs are above 4,500 or so, but once the transmission upshifts the rate of acceleration drops significantly as if VTEC is disengaging. Once the RPMs rise past 4k again, it continues to accelerate normally. For example, the RPMs get as high as 5,500 then when it upshifts, they drop to around 3,500, the rate of acceleration decreases substantially, then once the RPMs are around 4,500 it takes off again like a rocket. So irritating. What could be causing this to happen? The oil level is fine, but I have a minor leak in my spool valve. Although I can't imagine such a minor leak would cause enough pressure loss to affect VTEC operation yet not set off the oil pressure light (I have no error codes). I've only had the car for a couple months and hope this isn't "normal". Low and moderate acceleration are fine. Probably because I am not in VTEC territory.

 

What year make model engine transmission?????????? Need to post these things for people to help.

 

My fault. It's a 2011 Acura TL SH-AWD with 66k miles (3.7L J37A4 motor).

 

Take it in to the acura dealership.

 

Turns out I wasn't flooring it. At WOT, I don't get the hesitation between gear shifts. However, it doesn't seem normal to have to floor the pedal to keep VTEC engaged. Base on engine load, vehicle speed, and throttle position, it should stay engaged IMO.

 

ideal vtec engagement is rpm based, NOT throttle position based. vtec is not a power adder, it is a second cam profile. cam profiles only work in specific rpm ranges. the entire purpose of vtec is to have power at high rpms AND have good torque, throttle response, and great gas mileage at lower rpms. by having 2 separate cam profiles.

 

RPM is part of the equation, but not the only part. For instance, VTEC is not going to engage if you bring the RPMs to 4700 while sitting stationery in neutral. The ECU uses multiple inputs to determine when VTEC should be engaged and disengaged, and VTEC has hysteresis.

 

I'm also hearing a loud click click click sound a few seconds after shutting off the engine. Any idea what this is? I replaced the PCV valve the other day and from what little I could see, things looked pretty gunked up inside the intake manifold. I'm considering removing it and giving it a good cleaning. Someone on another site mentioned maybe my IMT (intake manifold tuning) butterfly valves are acting up. Maybe they're sticking? I notice a substantial increase in power when I get above 3,000 RPM and sluggish below. Driving me nuts.

 

Yes, but you were describing was WOT/no WOT. vtec engages at a specific rpm, not throttle position. You keep talking about flooring it, that means you are talking about throttle position.

 

I keep mentioning throttle position because VTEC engagement/disengagement seems to be different based on throttle position, which makes perfect sense. Why do you keep implying that VTEC is ONLY dependent on RPM? It isn't vacuum controlled.

 

Please show me an image of your vtec solenoid with a vacuum hose.

 

I said it is NOT vacuum based. Yes, you can set the RPM using your Flash Pro or whatever (not on the 4th gen TL though--at least not yet), but VTEC is not strictly RPM dependent. That's my point.