As usual, I have been driving the Integra to keep miles off of the other cars when the kiddos don't need a ride.
Vitals: About 165K miles, only routine maintenance and long-term EcoMods in place. Front LED turn signals + relay installed 1-month prior to problem.
Summary: Stalled, possible EGR / Fuel Trim problem, 39 mpg tank result without extra driving style effort previously used to achieve this FE range.
Condition: On the last tank, I was commuting in town with the manual TC locked, transmission shifted to 4th, and running about 2000 RPM. After cresting a hill and giving it light-to-moderate load, things started going wrong.
Event: The engine lost power and the tach swept from 0-2000 about 5 times -- more throttle was applied and TC disengaged to attempt recover from the problem. Unfortunately it stalled, so I popped it in neutral and tried to start it. It cranked and cranked with no luck, so I coasted into a parking lot.
Diagnostics: No new mods were made (except for LED turn signals up front to test a possible DRL setup) so that was written-off. Under the hood -- nothing that looked completely abnormal. The SG did show a new code: P0400.
I looked it up quickly on my phone and noted "EGR System Malfunction" for other models. After the time to look things up, the engine started immediately, and 400 miles have passed with no problems -- in fact, I recorded one of my best tanks at 39.x MPG and noted more power from reduced throttle input. No more stalling or any other problems.
Research: The isolated problem had me stumped, so I scoured the shop manual for something. First, P0400 is not listed as a trouble code. Second, there's no mention of an EGR system, except in the summary of "acceptable terms" with SAE document J1930 for 2001 and later models with Honda's old descriptor and the SAE Recommended descriptor. It's probably copied to all Honda/Acura manuals. I physically can't locate an exhaust gas recirc system in the manual, or on the vehicle.
The next assumption would be the Cat or O2 sensors -- which might lead to a lean condition and less fuel consumed. Premium fuel is used, with no knocking noted, even under high load and the occasional lugging from manual TC operation. So...
Stumped: I'm reaching out here -- other sources haven't offered anything. If it's an inadvertent EcoMod, I would love to know what it is! Otherwise, I'll (hopefully) continue to enjoy higher FE without trying REALLY hard to get these types of numbers.
-RH77