I didn't know that you changed the gearbox. Maybe you should list every modification you have done to your car so we have a clear picture of the situation.

Putting the original VEi transmission back in will help greatly with L/Km.

That is the number I was looking for. The G02 refers to the region and software for your computer. Since your region has higher octane gasoline, it is quite possible that you have different fuel and timing maps than our d15z1 motors in the US.


Your spark plugs are looking fine from the picture. Do you always use the same gas station to fill up? Sometimes if you change fill stations they use different additives in the gasoline that can change the coloring of the spark plugs.

It was just a exemple with some very bad sparkplugs (too cold), not with NGKZFR4F-11.

The sparkplug becomes too hot, then auto-ignition, ...
It's just some theory...

But I prefere use "stock" sparkplug for the moment.

Ok.

Engine modifications (not maintenances) :


66000km : I bought the car.

70000km : K&N air intake.
https://www.japancar.fr/forum/garage....d&image_id=782

80000km : NGKZFR6F-11 (no difference)

98000km : Remus exhaust (rear silencer)
https://www.japancar.fr/forum/garage....&image_id=2785

110000km : The problem begins.

12000km : NGKZFR5F-11

135000km : D15B2 4-1 exhaust manifold(so, now, no catalyst). The engine become more nervous when I push on the accelerator, so I feel more my problem.
At high load, I use a litle bit more fuel for the same distance.
https://www.japancar.fr/forum/garage....&image_id=4237

145000km : short gearbox
https://www.japancar.fr/forum/garage....&image_id=5384

VEI gearbox :
3.250
1.761
1.172
0.909
0.702
3.722

Short gearbox :
3.250
1.900
1.250
0.937
0.750
4.250

160000km : NGKZFR5F-11

165000km : Now.

To my amazement, The engine consume not more fuel for the same distance and same driving (Except when I push hard on the accelerator).


Yes, for +-2 years (+-45000km).

Is this true cruising on the highway? What is the majority of your driving? If it's city, short gear box will get you better FE. If it's highway, short gear box should get you worse FE. Although to be honest I never understood why since at higher RPMs the engine is outputting more horsepower per fuel consumed, so is at a much less fuel enrichment ratio at say 4000RPM as compared to 2700RPM when it's near full enrichment most of the time trying to maintain speed. But then there's the whole issue of amount of gas used to just have the engine turning at the higher RPM.

Yes.
Before, the engine was running at 3200RPM (130km/h) and now 3900RPM. But I must push less on the accelerator. Now, when I am in a climb, the engine load is low.
But if I often pushing hard on the accelerator, the engine consume more fuel that before.
80% highway.
20% city.

But I have read this : https://www.gassavers.org/showthread.php?t=2429
My reading is higher (1.3v) !!!

And I don't understant why it's so brutal when I quit "lean burn"...
Normaly,the enrichment is more progressif, no?

And I have read this : https://www.gassavers.org/showthread.php?t=3835

It's seems to be the same problem !

I know the motor isn't very similar but in my 1995 Acura Integra LS (Honda Integra over seas. Honda B18B1 engine) I've been getting the same issue you have, a bit of hesitation before power kicks in. I can floor it and it'll just kinda move along slowly then you feel the power punch in as if there was turbo lag or something. The car's all stock except NGK (Blue) spark plug wires and relatively new NGK plugs. The ZFR5F-11s as specified in the manual and on the valve cover. Think the O2 sensor is the cause? As far as I know, the O2 sensor on my car is original and it's always been in a climate that favors rust. The car has 132,638 miles on it. I've never had a CEL on the car, so I'm not sure if that's the problem or just the way the automatic transmission works.

If you aren't driving a VX, then your car should just take a regular 4 wire oxygen sensor. You should be able to get a new replacement for $50, if you DIY it. If your car is at 132,000, I would just go ahead and change it. The CEL does not always pick up a marginal sensor and the response time on the sensors get slower, over the miles.

On VEI's car, he needs to get a new sensor, as well, but since they run $350 or so, he doesn't want to do it, unless he is 100% certain and it isn't bad enough to be 100% certain. He could get the $79 unit, but if other peoples experiences are any indication, it very likely will throw a CEL code, until the car gets warmed up.

You should double check, on your sensor, to make sure it's the 4 wire unit, not the 5 wire LAF unit.

I'd do it myself but I'm worried about it being rusted into the catalytic converter so badly that I won't be able to get it out myself. Sounds like it would probably need a good dosage of PB Blaster to get it out. Sounds like a project for next summer for me :) My mileage is still above EPA average without much effort so I'm still happy with that (averaging 29mpg in mostly city driving, rated for 21 in the city, 24 combination)

Was it an O2 sensor, after all?
 

My VX is going through the same thing...and getting rougher all the time. I'm thinking it's the o2 sensor, but I'll double check on the plugs just to be sure.

Tambien, si vous voudrez practicer votre anglais avec moi, je voudrais practicer me francais avec vous. Merci, et bon chance!

i think its coming from lambda sensor
 

how you resolved this problem?
i have civic d15z1 vtec-e and this problem too :( .
this kind problem have all vtec-e engines.
i think its coming from lambda sensor