2001 with 39000 miles has developed a moderate bogging at anything over 50% throttle at any rpm. Once I pass 50% pedal travel it feels like the engine falls on it's face, it's definitely not a gradual thing. Any ideas what it could be in such a low mileage engine?
I've heard coolant temp sensor and dirty injectors as suggestions thus far.
I doubt it's the ECT... that sensor is not very critical.
Is throttle response normal under 50%?
Does this only happen at a certain RPM or at any RPM?
Does it idle normal or rough?
Does the power cut out completely?
Does it cut out abruply at a particular throttle position?
Is the check engine light on?
Possibly the MAP sensor (manifold absolute pressure) on the airbox. Injectors are a possibility... but your mileage seems too low for clogged injectors. Could be a bad PCV valve. It might be a problem with the throttle position sensor. It could even be something in the ignition.
Here;s what happens in most engines above 50% throttle.... at lower RPM's, going past 20% throttle does not increase the amount of power the engine puts out since 20% throttle is plenty of air for that particular RPM. At hgiher RPM's, the engine will switch over from a more econmical fuel/ignition map, ot one that provides better performance. This is why your mileage drops so quickly when you have a lot of passengers, head winds, driving at speeds over 70mph. In those conditions, the engine is no longer trying to run lean to conserve fuel, it wants ot produce more power.
Hope this helps some. hard to diagnose FI problems sometimes.
Took it to the dealer to see what they had to say this weekend. Upon their test drive the technician saw what I was talking about but needed to "diagnose" the problem to find the cause. Nine hours later my car is ready to be picked up and they say everything is normal, so no help there. Response is normal up to a certain point, depending on rpm, engine temp, maybe air temp etc. it can be at 25%, 50%, 75% throttle opening before the "bog" occurs. It is a sudden change and the engine, umm pulses? for a few seconds when it reaches this point before resuming a less urgent acceleration. Power does not cutout completely, acceleration is stronger at 50% throttle opening all the way to redline than at full throttle. It feels like it's abruptly reverting to a different mixture, like it's getting a reading that suddenly tells it to run rich or lean when it shouldn't. The vehicle has an Injen air intake on it, but it's been on there for 25k miles and this just started happening a month ago. The dealer ****ures me that the intake is not what's causing this ( I told them I would remove it if it were), and they "have no idea why it's doing this, but it's not a danger to me."
engine idles normally 99.9% of the time, only occasionally will it "choke" and fall to 500rpm or so, and no check engine lights are on.
It could be the intake and or the throttle body. I had an Injen intake on my Honda - made for a bit more rush at higher RPMs, but also had the same behavior you are experiencing after about 10K miles. What I found was the element was coming apart from the housing and the silicone ring holding the housing to the aluminum tube had worked its way loose. I also noticed that there was a bit more gum and varnish around and behind the throttle plate in the throttle body - don't know if that was caused by the intake - but after cleaning it out, checked all hoses from the intake, replaced the element and retightened the housing - performace returned back to normal.
Be sure your Air filter is not clogged. I know what thinking, but bear with me. My dad spent a lot of money replacing engine sensors before he gave up and went to the dealership for help. Turns out the Air filter was clogged. A casual inspection appeared ok, not clean but ok, but a close held up to the light revealed 75% of the light (and therefore air) was unable to penetrate the filter. The car ran great except on hard pulls or WOT. Above a certain point things seem to even out a bit but still felt sluggish.
I'm not sure if 2001 has MAP or AFM, but if it has AFM, the AFM (Air Flow Meter) could be dirty. Good luck... 
