Who replaced his LAF sensor (O2 sensor, Civic Vx)?
 

I am trying to get information about a possible relationship between a defective LAF sensor and a malfunction in "lean burn" :(


So, I have three questions :

Why have you replaced this LAF sensor?

Have you seen a difference in "lean burn", after replacement of this sensor? (Does the engine seems to work better in "lean burn", or not?)

Do you have a response time when you accelerate at low load and low RPM (with old / new sensor) ?


Thanks ;)

I have driven two different VXs now with recently replace sensors. Both have the same "response delay" and get about the same mileage now.

I think a good rule-of-thumb for the LAF is not to replace it until you are getting poor mileage or you have a CEL for it being faulty. They just cost too much to warrant replacing them for any other reason.

I just replaced mine, but don't have a baseline for mileage. Hell, I don't even know when I enter lean burn... Would be nice if a lean burn light came built in.

Is this exactly the same problem as me?
->
Yes, it?s true.
But, sometimes, I have the CEL (5 times a year).
And I think that my ?response delay? is more brutal than before.
I have controlled a lot of sensors (MAP, TPS, LAF), ignition, fuel filter, ... All seems to be OK.
So, I don?t if I must buy a new LAF sensor.

Ok, but when you drive at low load and low RPM, is there a difference with the new sensor?
Is it more pleasant to drive in these conditions?

VEI YOUR LAF IS NOT WORKING PROPERLY AND NEEDS TO BE REPLACED.

Your lag and stutter is NOT normal lean burn operation. Your car is exhibiting classic symptoms for a bad o2 sensor. No two ways around it. What Danronian was describing was normal lean burn operation which is a fairly subtle stumble upon acceleration, but nothing like what you are describing. Hope that clears it up! You need a new o2 sensor.

When you replace your o2 sensor, your car will no longer do the sudden power surge you have described. My car was doing this before I replaced mine. And it sounds like mine was not as bad as yours and yet I noticed a big difference with the new o2 sensor. You will notice a VERY big difference with a new o2 sensor. Where you should be putting your energy now is figuring out where you are going to get your new o2 sensor. Because they are expensive and not all work properly. Good luck! Wish I could steer you in the right direction but I really don't know where to point you since you are in Belgium! You could try the $79 one I bought, but seems like a bit of a gamble.

I know your opinion. But I would have several answers, several opinion before make a choice.

Ok, you have not this problem with your new sensor, but sometimes, you have the CEL. Your AFR is perhaps a litle diff?rent, more rich. I don't know.

It's difficult for me to explain my problem.
With the new exhaust manifold (no cat.), the accelerator response is different. The "response delay" is more "brutal".
But before, with d15z1 exhaust, I think I already had a "response delay" and some hesitations in lean burn. (More that when I bought the car).

Maybe I am crazy. It is possible that this is normal. I don't know.

I agree with 1993CivicVX, replacing your LAF would be the first step, especially since you've been getting the CEL code for the LAF. That is your computer telling you that the LAF isn't working properly.

Might I suggest that you de-carbon the engine as well. See if your local Honda dealer has the Top Engine Treatment (basically seafoam) or use seafoam. There is a link on how to use the seafoam/de-carbonizer in the VX links in my signature. Do that right before you replace your LAF and install your Catalytic Converter. That will help with the stumble.

Have you cleaned your EGR and EGR ports? If not, this can cause some stumbling on acceleration as well. There is also a How-To in the VX links as well.

You should also think about getting a replacement Catalytic Converter just for emissions sake. To save money you can get an aftermarket one for a regular civic and have a muffler shop, or yourself, install it after the exhaust manifold.

Once you've done all that you should be good.

I agree, sounds like some sound advice to getting your z1 working smoothly. While you're at it, I would also pull off the IACV (on the back of the intake plenum, facing the firewall) and make sure it's not clogged by spraying some intake cleaner into it. With that cleaned out, and the above suggestions put into place, the only other thing it could possibly be is that your timing is off.

If you have a timing light, you might want to check that and adjust it according to Honda's recommendation. The timing being off can also make your car stumble when accelerating.

edit:
With your different exhaust manifold, where is your LAF mounted? If it is too far away from the exhaust ports, the sensor might be taking too long to heat-up and stay warm, making it read incorrectly. I know on some aftermarket headers they have the 02 mounted behind the motor. For the LAF, I think this wouldn't be an ideal location for it at all.

Dan, thanks for adding in the IACV cleaning, I forgot about that.

The LAF is located at the collector just about 7-8inches down from where the OEM manifold would've had it located. Shouldn't be a big factor since it's still close enough and reading all the ports. Besides, that is what the heater circuit is for in the LAF as well. ;)

It?s very difficult to find this kind of treatment in Belgium.
And they often have a bad reputation.
Sometimes, this can be bad for a old engine. This can cause a loss of sealing (The carbon can maintain compression).

I have tried this product last year : https://www.wynns.be/product.aspx?nav...4&p=55964&l=EN


Yes I have cleaned the EGR.
https://img102.imageshack.us/img102/7292/04fg6.jpg
https://img297.imageshack.us/img297/248/01ps1.jpg

During one week, I have drove without EGR. But no difference.
https://img265.imageshack.us/img265/3706/03fh8.jpg

Last year, I have passed the pollution tests successfully.



I have checked the IACV. It?s seems to be clean.

I have checked this. It?s good.
https://img143.imageshack.us/img143/4268/02ov9.jpg

Before :
https://img175.imageshack.us/img175/1866/co02rz8.jpg

Now :
https://img175.imageshack.us/img175/6222/co08yj7.jpg

That is good that you have cleaned the EGR, now have you cleaned the EGR ports?
https://users.adelphia.net/~hagakure9.../EgrPorts1.jpg

That looks like it's the 12° timing mark (lights up when using a timing light to check timing) What does the timing look like when you check the TDC (Top Dead Center) mark against the TDC mark on the cam gear?

No, it seemed clean.
And I have the same problem when EGR is DISCONNECTED !




I don't understand your question.
Red mark = 16?
Black mark = TDC (0?), first cylinder.

^^^ok, there are two different things to check when you "check timing".

TDC is the black mark....when that mark is in the pointer, is the TDC mark on the Camshaft pulley at the TDC mark on the inside of the upper timing belt cover?
https://www.we-todd-did-racing.com/we...NDE%3D.jpg

The other way of checking timing is to have the car running and see what the ignition timing is set at. That is when you use a timing light and look at the pulley to see where the timing mark is at. Like the picture you posted.

I hope that makes sense to you. Let me know if it doesn't.

How did you check the EGR ports? Did you remove the EGR plugs in the intake manifold and check?

I don't think it is possible it is normal. I think no one has replied to that comment because I think the opinion of everyone else is also that it is not normal. It's wishful thinking my friend in lieu of a $320 fix to your problem. Granted I don't know much about cars, but the little I've picked up about my car on this forum leads me to believe there is little other recourse for you in the matter of your stumble/power lag/power surge issues upon acceleration. I can also say that with my car the problem was worse the lower the RPM, which seems to be true for you as well (at 3900RPM you said the problem was not present) I did have the same problem as you. And through the same advice the people here are giving you, I applied to my own car and the problem was fixed. If you search through the forums you'll find other VX owners who had similar problems fixed by replacing their old o2 sensors. o2 sensors do not always throw a CEL when they are not performing at their best and could use replacing. My car was not giving me a CEL when I replaced the o2 sensor, and yet the o2 sensor was the main culprit to the problem. You may want to try www.honda-tech.com to see if you can elicit a different opinion over there, tho.

The replacement of the o2 sensor had the largest positive effect for my car. The right spark plugs also had a big effect for improving the stumble problem. And I think the other things mentioned can't hurt and may help with that specific problem. Anyway, if I come across a little brusque, I don't mean to be rude (look at my title, I sometimes have a hard time being polite) I am trying to help you. Or at least save you some time.

One more thing: it seems that the life span of the o2 sensors is around 170,000 miles, give or take a few 10k. Your car has around 165,000? Basically, there is no indication that your o2 sensor might be fine, and lots of indication that it needs replacing. Namely the CEL, the bad stumble/power lag/surge and the fact that nothing else you have tried has fixed the problem. Anyway, I suppose you can't be too certain about something when it's as expensive as the o2 sensor to fix.

Ok, now I understand what is ?timing?. The word is completely different in French :o
I was thinking about ignition.

Yes, the marks are correct and I have checked my ignition timing (my picture).

But I must replace my timing belt (normally next month).

I have checked under the EGR valve and no carbon.
But, I have the same problem (lag) when the EGR valve is disconnected. So, I think that EGR is good.

Or if some smart member could design a circuit to turn on an idiot light when in lean burn.

This idiot would buy one!

I'm working on it soon, it's on my list of things.

That would be nice. :D

That would be pretty sweet TomO. I'm assuming at this point that I'm in lean burn whenever the pedal is feather footed, and I'm out of lean burn when I feel that little power kick and the throttle won't give more power.