2001 Buick Lesabre loses power at highway speeds

Hello. My 2001 Buick Lesabre 3.8 loses power at highway speeds, sets a PO101 code (MAF sensor). I have replaced the MAF sensor 3 times, as well as the coolant temperature sensor, the crank position sensor, the throttle position sensor, the MAP sensor, the intake manifold gaskets (upper and lower) , the pcv valve, the egr valve, the Idle air control sensor. After cruising at highway speed for about 3 miles the car still loses power for about 20 seconds then gradually regains power only to repeat the fault again 3 or 4 miles down the road. Otherwise the car has plenty of power quickly achieving 100+ mph going though the gears smoothly and normally. I have inspected the intake plenum and vacuum hoses for leaks and have found none, all in very good condition. The car ha 122,000 miles on it and has been well cared for, very clean under the hood with no leaks. I did reduce the egr chimney size to 3/8" while replacing the intake gaskets and that reduced the symptoms somewhat, ie the car only loses about 15 mph instead of dropping to about 25 mph before recovering. Anyone have any ideas please?

A high resistance on the ground circuit of the MAP sensor can cause this DTC to set. Noise can be induced into the wiring from wiring running to close to the ignition coils.

Thank you.
When using the MAP ground wire to ground my volt meter and the red wire of the meter on the battery+ I get a full 12+ volts so I assumed the ground was good. Am I overlooking something?

This just be might a partially restricted catalytic converter. It may be somewhat intermittent due to alternate heating and cooling of the converter causing expansion and contraction inside.

The symptoms are very similar to the symptoms I had with my 2002 Malibu. It lost power on long hills on interstates then recovered when the road leveled out. A new converter fixed it. I never had a check engine light.

It’s intriguing the problem reduced when you reduce the EGR action. There’s lots of possibilities, but that seems an important clue and I’d be inclined to focus on that until it is otherwise proved the EGR is not the cause.

I wonder what could be triggering the EGR? Usually it turns on during rapid accelerations. Does this happen when you accelerate, even briefly? I’m wondering if the EGR is turning on, then sticking open for much longer than it should. It’s possible it is sticking on something inside the engine where it fits, like some gunk or a carbon deposit, not a fault of the EGR valve itself I mean. Maybe remove the EGR and get a mirror or whatever you need and carefully inspect that area. Also make sure the EGR seats correctly on its mating surface and use a new gasket. \

On my Corolla the EGR operation is fairly complicated. The ECM (computer) can turn it on for example, independent of anything else (like intake manifold vacuum, etc) that causes it to operate. There’s a electric operated solenoid that does it. If yours is the same, maybe a glitch in that device?

What I’d be inclined to do as an experiment is to come up with a way to completely eliminate the possibility of the EGR valve opening, and if that fixes the problem, you know what area to explore next. Don’t continue to drive the car with the EGR disabled tho as doing so could damage the engine.

George, Apparently acceleration does not have anything to do with the OP’s problem as he states he can go 100 MPH + Reckless as that may be.

Volvo … I wonder why the EGR mod seemed to help then? Maybe it wasn’t the EGR mod that helped, but that the intake gaskets were replaced.

A plugged/partially plugged cat is not hard to diagnose. You just need the proper tool to check backpressure.

“Otherwise the car has plenty of power quickly achieving 100+ mph”

Doesn’t sound like a plugged cat if the car can do 100 mph.