Civic D15Z1 problems

[Stubby79]

Fingers crossed!

You could try bench testing the O2 sensor. But...they work differently (obviously) than normal ones. They create current rather than a plain voltage signal. It would take a lot more messing around...hooking power up the toe heated circuits, making an appropriate dummy load to dump and measure the current in to...and then figure out how much current it SHOULD be creating. And if you get the dummy load resistance wrong, your readings will be useless anyway.

The current is bi-directional, to boot. 0 current tells the ECU that it's stoich. Which suggest that if there's something wrong with the sensor - where it puts out no current - the ECU is going to read it as running stoich even when it's not. Quite an annoying fail state. No heated circuits would result in the same, except when you're running it long and hard enough to get it up to temperature.

Maybe if you had driven on it longer, the ECU would have recognized that it's not getting any response from the O2 sensor, and would have thrown a code. Dunno. Dunno how much driving you did with it like that. Dunno if the early ECUs would test the heated circuit or not, like more modern ones do.

Good choice, ordering a new o2...just painful on the pocket book. (I'm cheap, wouldn't do it unless I had to!)

[Tippaleipa]

I drove maybe under a mile with o2 connected, because the hesitation scared me badly, i thought that my rebuilt engine is going to explode

[Stubby79]

Since there's many variables, it was better to be on the safe side.

At least you know it works well with the o2 unplugged; it's mechanically sound. You can do some deep-diving if it still misbehaves with the new o2. And longer drives, if it still acts up.

[Tippaleipa]

One update. Few days ago i noticed that my spark plugs were wrong. They were denso q20tt and i changed them to denso kj14cr-l11. Plugged my o2 sensor back and it was little bit better in cruising speed. In first and second gear its fine, no hesitaiton at all, but when i change to third gear and try to accelerate it just wont. After very slow acceleration i finally get to cruising speed, like 50mph it just backfires and bogs. Tried to drive it harder but no effect. Works lovely before it hits operating temperature. New o2 its still on its way, i going to change it when it arrives. But why the lean burn is kicking in middle of acceleration?

[Stubby79]

Maybe in the middle of acceleration because that's when your current O2 sensor finally heats up enough to start responding. These wide band o2 need to be around 1500* or something like, iirc, which it's not going to get to except under heavy load or with the internal heaters working.

Had to put a heated o2 sensor on my Miata to get it to stop running rich - o2 was too far downstream on the header to stay warm - and that wasn't even a wide-band. If I drove it spiritedly, in the summer at least, it would warm up enough too.

PS: I found even cheap wide-band o2's on Aliexpress, so if the one goes on my insight, I know where I'll try first.

[Tippaleipa]

Okay, so today i went to work and came back with o2 connected and it gave me code 41. Didin't light up CEL tho. I believe it means that the heating circuit of o2 sensor is bad?

[Stubby79]

Consensus agrees with that assessment.

[Tippaleipa]

Small update again. Yesterday i changed brand new ntk wideband and it changed nothing. Lean burn still kicking in middle of acceleration in third gear and it pops and bangs when cruising. No CEL but gives code 41. I have to check the o2 heating circuit. I also have the cold start problem. I have to crank two times, and in third try it starts right away perfectly. I have measured the coolant temp sensor and iat and they were good. Tried to prime fuel pump multiple times but it still needs few tries to start.

[Stubby79]

I know you said you checked and fixed a broken wire going to the o2...perhaps there are still issues with the wiring.

Good idea checking the temp sensors.

I see there is a "mod" done on the insights to help keep it in lean-burn as much as possible. It's a throttle position sensor "smoother". If your TPS isn't responding fully, or the signal isn't getting to the ECM, it might be keeping it in lean burn. Which I mentioned before, but don't remember if you checked it or anything.

Pretty much guaranteed it will stay out of lean burn without the O2 sensor telling it all is good, so even if the TPS isn't working, unplugging the O2 would keep it running in "normal" mode.

Of course, it could be totally unrelated. At least the TPS is easy to check...ignition just needs to be on, doesn't need to be running. Presumably a 5v signal that will vary according to how open the throttle is. Can check that it's getting said signal at the ECM too, if you find the right wire.

I think you said you checked/cleaned the EGR. I really should read back but...I'm lazy.

The code and behavior still point to the O2 though. TPS is a quick/easy check, then I'd go back to the o2. Still have +12v and ground at the heated circuit with the sensor plugged in? Not showing any weird voltages on it? Some resistance on the +12v side would end up with lower voltage or voltage falling flat on it's face when it's loaded/plugged in. Resistance on teh ground side would end up with a + voltage reading (more than a couple of hundred millivolts) on the ground side.

Blah, blah, blah...chasing electrical gremlins is fun, isn't it?

[Tippaleipa]

Tps has the +5v, signal comes to ECM and also has sensor ground. I dont have the egr control box so the vacuum to lift valve is blocked and it throws code 12 which is egr lift valve. Engine worked great in donor car without egr so i ruled that out. This lean burn bog/misfire seems to be common problem with these things.