First time posting...Bought the 99 accord exv6 about 6 weeks ago and total headache since.
Thought it was awesome at first but after my first 30-minutes of highway driving at consistent speed (over 45mph) it starts to loose acceleration (with foot on gas pedal), drops about 700rpm then "catches", surging back up to normal and repeating the whole thing again immediately after for up to 5 minutes at a time. comes and goes during a normal drive.
Have been to the mechanic & dealer. Mechanic thinks likely ECM, dealer advising me to change plugs & downstream (heated) O2 sensor. Having my mechanic replace plugs, wires, cap...if that doesn't do it then O2 sensor I suppose. What is the recommended replacement O2 sensor of this kind? I would rather seek it outside of the dealer because of the price. Searching has brought me to the denso 234-4621, is this correct?
Any other suggestions about this problem welcome, it has been sucking my life out since I got the car over a month ago. Thanks so much!!

 

Have tried the following with no luck:
Distributor
Catalytic Convertor
Fuel Pump
EGR replace & Pipe cleaning
Transmission Diagnosis came back clean
Gives codes p0171,p0131,p0300-0306

 

P0171 is Fuel System Too Lean
P0131 Primary Heated Oxygen Sensor Circuit Low Voltage

That would point to the primary O2 sensor instead of the rear (secondary) sensor.

The Honda part number for the primary is 36531-P8C-A01, which would cross-reference Denso 234-4099.

 

So add to the list of stuff tried: new spark plugs (NGK platinum), wires, rotor, cap, & heated O2 sensor. Going to try the ECM next, have heard that it will need reflashing by the dealer, can anyone else do this? It would be great to avoid the dealer, they upcharge 300% or more on everything....

 

Solved! Finally found a guy willing to diagnose the problem instead of throwing parts & $$$$$ at it first.
THe Catalytic convertor was the offender. It was so clogged that when it got especially hot it was causing BOTH O2 sensors to completely crap out. I had replaced the Catalytic convertor early on but when it didn't solve the problem I put the old one back on in an attempt to save $ for the real problem. It hadn't worked because the O2 sensors were already fried by it. When I replaced O2 sensors and not the Cat it fried the new ones.
Only when a total wizard explained why I should change all three (Catalytic Convertor, up and downstream O2 sensors) did the problem clear up. Has been great since, check engine light totally off and I can get back to loving life.
TAKE NOTE! YOUR CATALYTIC CONVERTOR CAN REALLY EFFECT THE PERFORMANCE OF THE VEHICLE!!!