Correct D15Z1 leanburn info

[slownugly]

Agree to disagree. If you ever get a chance post some pics of your system. It's not that I don't trust Honda diagrams it's that I don't trust ANY factory diagrams. I've been screwed over too many times in the past at my shop.

[cbaber]

FOLLOW UP: I have now confirmed that O2 sensor position in the exhaust does have an impact on the ability to engage lean burn. Immediately after swapping my exhaust manifolds my lean burn functionality returned (indicated on the ScanGauge).

The problems created by moving the primary sensor downstream:

1. Stalling/sputtering/loss of power while accelerating (because of EGR, the ECU is looking for feedback instantly but the delay created by moving the sensor creates the issue)
2. Sputtering/loss of power when going into lean burn. When conditions were met for lean burn it would sputter/cut out and then I felt it kick back out of lean burn and return to normal A/F ratios. It would try repeatedly but fail to ever stay in lean burn

I can also say that the EGR system, while it is a part of reducing the emissions created by lean burn, is not required for operation. I have a faulty EGR valve, and a symptom of it is sputtering under engine load while driving. To correct it I disconnected my EGR valve and the symptoms go away, but I still have lean burn functionality. Although I will add in that EGR enhances lean burn operation and overall fuel economy, so it's best to keep it working. I just need to buy the $200 valve to fix my issue.

Originally Posted by cbaber

I've not been able to confirm that O2 sensor position is a factor. As I posted earlier, I swapped my stock exhaust manifold for another Civic setup, which the O2 is at the back of the manifold near the firewall. Even with that setup I could still engage lean burn. My problem is the O2 sensor. Shortly after making my earlier posts my factory sensor went bad, and I bought a cheap replacement. After buying the replacement I can no longer engage lean burn without the engine hesitating and stumbling when it tries to engage.

I've bought another manifold that moves the O2 sensor back up next to the exhaust ports, but have yet to install it. If that solves my problem then I will report back. If not, it's my cheap O2 sensor that cannot handle the lean burn.

[greasemonkee]

Without the egr valve opening properly it will have a tendency to detonate for several seconds after applying WOT. The ecu adds a considerable amount of timing anticipating a slower burn/inert gasses in the chamber.

Interesting - All these years I thought the absence of the egr would activate the MIL.

I posted an egr valve repair thread on here somewhere, for sticky diaphragm-to-sensor pins, perhaps it will save you some trouble.

[cbaber]

Originally Posted by greasemonkee

Without the egr valve opening properly it will have a tendency to detonate for several seconds after applying WOT. The ecu adds a considerable amount of timing anticipating a slower burn/inert gasses in the chamber.

Interesting - All these years I thought the absence of the egr would activate the MIL.

I posted an egr valve repair thread on here somewhere, for sticky diaphragm-to-sensor pins, perhaps it will save you some trouble.

I do have a CEL for the EGR. When I had it connected I also got a CEL, it's the same code, insufficient lift/flow. I've tested the EGR per service manual and it indicates it is bad. I've also done the proper cleaning of the EGR passages under the fuel rail and the passages that go into the intake. I'll search for the thread. It would be nice to just repair the valve instead of spending $200.

It came as a complete surprise to me that lean burn would work without EGR. Previously, before I changed my exhaust manifold to the correct setup, I disconnected the EGR because that would actually prevent the car from going into lean burn. If I had the EGR connected it would cut out and stumble when trying to go into lean burn. If I disconnected it the car would not try to go into lean burn and I could drive it normally, and still get 45-48 MPG.

But like I said all I did was change the O2 sensor position back to where it was in the OEM setup, and even with the EGR disconnected the lean burn activates now without an issue.

[jeffcat]

I'm really glad I found this thread as I was going to clean out the PCV system today. I still have to do the breather chamber yet, but I'll get that when I take the intake off.

Anyways, I noticed the previous owner put the PM6 code PCV valve on my 94 VX at the intake manifold location. I popped it off and cleaned it out...I think it was actually stuck. Being a PM6, it had the guts in it. After that, I went down to the OTHER PCV valve attached to the breather box. I couldn't pull it out due to the stupid clip being turned the wrong way, but I was about to clean it out regardless. It was a brown PCV valve that had guts in it too. So, I cleaned both and hooked it back up.

My question is can anyone definitely say as to whether there is suppose to be 0, 1, or 2 PCV valves on the VX? Based on what I'm reading, it seems like there was ORIGINALLY only 1 PCV valve attached to the breather chamber, then the gutless elbow at the intake, where I currently have a PM6 PCV valve.

Seeing this, should I take the guts out of the PM6 PCV valve near the intake and then just run the original PCV valve near the breather?

[WD40]

jeffcat, you are correct.
There should only be the lower PCV valve the upper is simply an elbow, remove the valve cut off the bottom remove the guts replace as an elbow.

[jeffcat]

Originally Posted by WD40

jeffcat, you are correct.
There should only be the lower PCV valve the upper is simply an elbow, remove the valve cut off the bottom remove the guts replace as an elbow.

Thank you. I actually just did it this morning and I have to make a 2.5 hour trip this week, so I'll see if it did much in terms of fuel economy, although I'm on a small sample size. I was hoping it would eliminate my low idle problems, but unfortunately it didn't. I didn't notice much difference in driveability, but I haven't had it up to 55+mph yet. I took the IACV off and cleaned it out, put a new air and fuel filter in, cleaned the PCV, and it's still low around 400rpm(IACV still works). I went through the service manual procedure of turning the idle up on the throttle body and went out about 3/5th a turn and it helped a slight bit(450rpmish), but not much. I'm not quite sure what the deal is there, so I'll see what happens after I take the intake off and give a cleaning.

[92civicvx]

Originally Posted by jeffcat

I'm really glad I found this thread as I was going to clean out the PCV system today. I still have to do the breather chamber yet, but I'll get that when I take the intake off.

Anyways, I noticed the previous owner put the PM6 code PCV valve on my 94 VX at the intake manifold location. I popped it off and cleaned it out...I think it was actually stuck. Being a PM6, it had the guts in it. After that, I went down to the OTHER PCV valve attached to the breather box. I couldn't pull it out due to the stupid clip being turned the wrong way, but I was about to clean it out regardless. It was a brown PCV valve that had guts in it too. So, I cleaned both and hooked it back up.

My question is can anyone definitely say as to whether there is suppose to be 0, 1, or 2 PCV valves on the VX? Based on what I'm reading, it seems like there was ORIGINALLY only 1 PCV valve attached to the breather chamber, then the gutless elbow at the intake, where I currently have a PM6 PCV valve.

Seeing this, should I take the guts out of the PM6 PCV valve near the intake and then just run the original PCV valve near the breather?

I did a lot of research on this and from the factory there should be an open elbow that attaches to the IM. The working PCV valve goes into the breather box under the IM. I just replaced mine with a Oem replacement from honda. Previous owner had a second pcv installed where the open elbow should be. Chopped it open and removed the guts than reinstalled it. Haven't felt any difference in drive ability since I did the work.