Hello, I am a newbie. I come from Belgium.

It?s difficult for me to speak in English, but I will try to do my best...


My car is a 1994 Honda Civic VEi.

It?s a D15Z1 engine, as Civic Vx.

I have some little problems with the engine.


At low RPM (< 3200tr/min) and low load (I don?t know if it?s the good word, -> Low pressure on the accelerator pedal), I have a response time (lag ?) before the engine accelerates.
(I am pushing slightly on the pedal and nothing happens, during less than 1 seconde. Then, suddenly, it accelerates sharply).

I don?t have this problem when the engine is cold or high RPM or heavy load.

The ?check engine light? appeared 3 times this year. (Code 48, LAF sensor).


Did you ever had the same problems?

Are there links between the LAF sensor and my problems? Or is it 2 different problems?

Sounds to me like the LAF might be almost ready to be replaced. Is the sensor old?

A slight lag in response time for the lean-burn on the d15z1 is something I've come to be used to when driving my civic.

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It sounds like there might be a link between the LAF and the lag, can't be sure, of course, but that's what it sounds like at this point. The lag could be caused by bad o2 readings not delivering the proper amount of fuel quickly enough.

Welcome to the site!

It sounds like changing your LAF (Oxygen Sensor is also what it's called) is going to be a great starting point. Just be warned that it will be expensive as it is an L1H1 sensor. Your best bet would be to find one for sale on eBay from a seller that ships internationally.

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Oh, the answers are quick on this forum !!!


Yes, I also suspect the LAF sensor.

I checked :
MAP sensor.
TPS sensor.
EGR valve.
LAF sensor.
…

I tried a other ignition distributor.

I have :
New air filter.
New fuel filter.
News Spark Plugs.
News ignition wires.


The LAF sensor has 165000km, like the engine.

The signal of the LAF sensor is good but impossible to control the response time.
And impossible to know if the value is not poorest in reality.

But I hesitate to replace this sensor. Some guys have the same problem with this engine but with a new LAF sensor (but I don’t know if it is really the same problem or a ignition problem).
And this sensor is really expensive.


Did you have the same problems (lag)?


I have two other little question :

What is the "clutch switch" (It is used to what?)

Is it normal that the engagement of the VTEC-E system is between 2500RPM (heavy load) and 4000RPM (low load)? In the documentation, this seems to be much lower...



My measurement (Voltage solenoid) :

Your Vtec-E solenoid activation is in working order as shown by your video.

What brand and number is on the new spark plugs you have put in the car? The d15Z1 motor is very picky about plugs.

I can't recall the exact ECU pins, but I see you know how to use a Volt meter (awesome!). you can check the VX links in my signature and check the one titled "VX Lean burn Monitor". That will show you which ECU pins to connect to with the voltmeter and check the readout of the LAF. If it seems sluggish and takes a long time to react to the throttle change, it is getting time to replace it.

The lag that you described earlier was the same experience I was having with my VX when I got it. The LAF had about 280,000 miles (450,616km) on it at the time and was getting tired. It also had the wrong number plugs in it as well. I changed to the correct plugs and I changed the LAF and the lag problem was almost gone. There is still an inherent lag in the d15Z1 motor due to the nature of the lean burn cycle.

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NGK ZFR5F-11 (In Belgium, i have the choice between ZFR5F-11 (stock) and ZFR6F-11 (warm climate).

Thank you for this link. Very good.
I have made this control 6 months ago. But my Values seems to be a little bit differents. I will retry this week to be sure.

That's odd, in the US the stock plug in the d15z1 is NGK ZFR4F-11.

I know that my motor had the ZFR5F-11 in it when I bought it and that caused some hesitaion due to the wrong plugs.

Great, glad to help out. I'm looking forward to your updated results.

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Welcome to GasSavers. The clutch switch is a safety interlock switch which is used to make it so you have to depress the clutch, in order for the starter motor to engage. The switch is located under the dash, at the top of the clutch. (You can put a jumper wire on it, to bypass the switch/interlock, done.)

I have checked my LAF sensor.

My voltmeter was connected near the LAF Connector (not ECU). Normally this is the same voltage.


Sensor 2 (D14-D16) :

Idle :

Video :




Sensor 1 (D8-D16) / Sensor 2 (D14-D16) :

Acceleration :
/
Video :
/

Deceleration :
/

Low RPM, low load (-> ?lag?) : The response of the accelerator pedal is not normal. The engine accelerates too slowly with some small hesitations (Except if I push harder on the pedal) :
/
Video :
/

Do you think that is too lean?


Just after ?lag? :
/




I have this switch but I can start the engine without depress the clutch.

At that RPM could the lag perhaps be the VTEC kicking in?

Do you have NGK ZFR4F-11 spark plugs readily available? If you do, swap those into your car and see if the hesitation is reduced then.

I'll have to watch the video to see the response time of the LAF as I cannot watch Youtube videos at work.

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At that RPM, yes it would be possible but I don?t think so.

Look this video :


(It is a climb). I push slowly on the pedal but the car doesn't accelerate, there are some small hesitations. Suddenly, with the same constant pressure, the car accelerates faster.
And no VTEC at that RPM (12 valves).


I don?t know, this is normaly not the good spark plugs for Civic VEi. I always had ZFR5F-11 and no problem before.
I think that the spark will be better with ZFR4F-11, perhaps less hesitations, but the heat will be too high (bad for the engine).




And sorry for my bad English, I hope you understand what I want to say lol

That is the motor coming out of "Lean Burn" mode....looked pretty normal and a decent response time of the LAF to me.


Does your motor have a sticker on the top timing belt cover that shows the recommended plugs?
Like this (picture from my d15z1):

The lean burn really needs a hot plug to ignite the lean mixture well.


Your English is very good! And your use of Youtube is a great help as well. Keep it up.

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I don't understand why I have 1.3V in acceleration (low RPM, low load) and 1.1v in deceleration.
Normaly there are no injection in deceleration...

I think 1.3v is perhaps too much. I push the accelerator, so more air intake, but the car doesn't accelerate (like no more injection). I don't know if it's normal during "lean burn".

When I have bought my car, i haven't this problem.


-------------------------------

What is the english word for "air/fuel"? Is it "mixture"?

This can be rich or (???) What is the correct word : "poor" or "lean"?

Yes.

Upon looking over my lean burn thread, 1.1V on deceleration is a bit strange. One possibility maybe be a leaking injector, or having a high electrical load.

1.3V is normal "rich" for acceleration. I have seen it as high as 1.4V.

Are your driving habits the same as when you first had the car? How many kilometers were on the car when you bought it?

In English, we use the phrase "air/fuel mixture" or "air/fuel ratio". It can be rich, stoich, or lean.

That is interesting that it suggests the ZFR5F-11 plugs on the sticker.

Could you please post the numbers on the side of your ECU for us as well? I am interested to see if the ECU version is different than the US model.

Thanks!

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As I understand it, that middle number is the heat value of the spark plug. Hotter plugs have a deeper well around the center electrode, reducing heat dissipation to the cylinder head which results in a hotter center electrode.
A hotter plug shouldn't cause the engine to overheat, though it's possible it could cause pinging. What's the typical octane rating of gasoline in Belgium?

66000km

Now : more highway.
But I doesn't have problems on highway because the engine is running at 4000RPM (short gearbox now).


The Honda reference for my car is : 37820-P07-G02. Is it this number that you want?



Yes, that's right.
Hotter sparkplugs : can perforate a piston.
Colder sparkplugs : fouling of the spark plug, bad ignition.

95 or 98.
For my car : 95.
What is the ocatne rating in US?


My sparkplugs, last month :

That seems me too white.
Before, they were more gray.

plugs look good! It's a lean burn engine remember.

I kinda doubt that, but I don't blame you for being cautious. You would have to be running lean under high load to get the piston hot enough to melt. Detonation can break the ringlands off the piston or occationally punch a hole in it, but that generally only happens with cars running aftermarket forced-induction (supercharger, turbocharger, nitrous) systems.

87, 89 and 91 are most common, but as high as 95 can be found at some stations.

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.

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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.


80000km : NGKZFR6F-11 (no difference)

98000km : Remus exhaust (rear silencer)


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.


145000km : short gearbox


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.

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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 : So I measured my o2 readouts on the new VX..
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 : New VX O2 sensor installed

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.

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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)

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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!

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