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Long Version- I believe the word you may be looking for is "Quenching"! I am an original owner of a VX and after replacing the O2, which only gave a CEL on deceleration I to also "changed the plugs", air filter etc, but started to experience some severe stuttering after reaching full operating temperature when the engine starts to use the O2 readings and go into lean burn. It was bad!! Thinking that perhaps the Non-OEM replacement O2 may be at fault after hearing that "the VX is picky about O2 Sensors" (actually it's an LAF in the 49 State Model 5-Wire) I nevertheless began to systematically eliminate all the other "Usual Suspects" to be sure. This included the EGR, EACV, Distributor, Vacuum Leak tests, MAP Sensor and the entire fuel system (including cleaning my injectors off car), Seafoam, draining the gas tank and trying Premium Grade Top Tier Gasoline. Everything checked out and there were no CELs! Some of this made some improvement, but the hesitation continued and at times it even seemed to be worse! But one day while on a test drive at the end of this month long odyssey I decided to drive a bit further and go to a Parts Store that carried NGK Plugs and got the Honda recommended ZFR4F-11 Plugs (NGK Stock #4043). This COMPLETELY solved the problem. You can go to the NGK site and read more about “Quenching.” But here’s what takes place on the VX. At full operating temperature it begins to consider the O2 data and goes from rich to lean burn particularly at under 2500. At under 2500 RPM only one intake valve fully opens (the other only partly opens to prevent a “gas puddle from forming” (ref. Honda Shop Manual). This lean air fuel mixture is much harder to ignite particularly under load and if not done properly it sets the O2 (LAF) and ECU into chaos. However, when the VTEC-E gets to around 2500 it goes into full 4-Valve Operation, with different Valve Timing and Lift and a Richer Fuel Mixture, all for sake of more power. At this point or before the engine is at full operating temperature and also running rich a non- NGK plug behaves better so the engine runs smoother. By the way, you can’t really tell full operating temperature from the gauge you have to drive about five miles even in hot weather. This was the best $8.00 I ever spent and ironically cheaper than the Platinum plugs that performed so badly. I’m also really glad that I didn’t throw a lot parts at it.
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