I've got an '02 3.8 liter with 76K miles. Past week has suddenly lost power on hills and on quick starts. Otherwise runs fine, no DTCs.

Hooked a vacuum gauge to the intake manifold. At idle, it reads 20 inches vacuum, steady.

On quick accel to 3000 RPM, the vacuum drops quickly to as low as 5 inches, but within a second, comes back to 20, maybe 21-22. The gauge needle starts shimmying at that speed though, and not from the vibration of the car.

I never see the slow drop in manifold intake vacuum that is said to happen with a clogged converter. But since failing converters are so common on this vehicle, it still seems to need looking into.

Does anyone have any experience with this?

Thanks.

 

You could try temporarily unhooking the exhaust downpipe and seeing if the bogging went away.

Or you can have an exhaust shop do a back-pressure test

 

My question is about the intake vacuum, and what constitutes a normal or abnormal reading.

 

those vacuum pressures seems normal....

raised at idle and fall during acceleration....which is normal....also vacuum varies while driveing....

Im with mike on this one(chibi)....get the back pressure checked...or disconnect the down tube..to see if power gets restored....