Hey guys,
I have a 98 Ek D16Y4 civic, and is running rich. This is the model without o2 sensor, so i installed a set of headers and an o2 and gauge and now i can see how bad it is.
Motor has previously an old ladys car and after me doing 50,000k of driving it burnt a valve and pistons were covered in a thick carbon layer. Was also very sluggish. Been re rung, new valve etc.
Anyway i want to know how the ecu alters the mixture, I thought that the motor ran rich on start up and leaned out when the motor got to operating temperature.
Mine will start at about 13.7:1 for a minute , then slowly goes richer until the motor is warmed up and it will cruise at 11.7:1 and wot is about 10.7:1.
I have checked voltages on all the sensors , temp tps map and fuel pressure, they are all ok according to charts. both Timing belt and ignition is fine
On my second o2 sensor now and don't want it doing what it previously did.
Does anyone have any suggestions?
Cheers

 

Which ecu are you running? Stock injector and fuel pump?

 

Everything thing is stock from factory except for headers

 

D16Y4 isn't a north american motor. What market is your 98 civic? USDM and CDM both don't have any model in the 96-00 range that did not have an o2 sensor for fuel trim.

 

New Zealand and probably Australian market and more.my ECU is 37820-P2K-V01 and I searched that and found out.
https://nzhondas.com/topic/94901-p72-ecu-in-nzdm-ek-p2k-ecu-help-needed/

 

NZ got all sorts of funky stuff like this.
check the intake manifold temperature sensor and engine coolant temperature sensors. if either other of those are giving the ECU the wrong data it will result in A/F's that are off as you describe.

 

^This. If there's any way to be connected to a scan tool and jiggle the plugs around while watching the values, you may be able to find your culprit.

Generally, when you cold start the ecu piles a bunch of extra fuel in to hit a richer target to help get it going and warm up faster. This number tapers down as coolant warms up. It also applies another post-start adder on top of that tapers down quickly after firing over a number of engine cycles. 13.7 ~= .93 lambda, that seems reasonable for a warmup mixture if not a touch lean. The rest is obviously stupid rich.

P2K ecu is the two-connector style, right? Should have had a one-wire O2 sensor, they also batch fire the injectors in pairs. Some other threads I look at real quick seems to think you should have a one-wire sensor on a '98 too: o2 sensor for d16y4 EK (ozhonda.com)

Is there a white wire in ecu-D20?

 

This **** model didn't come out of the factory with an O2 sensor .
my fuel starts, when engine is first turned on, at about 13.7:1 and slowly gets richer as it warms up to about 11.7.
It should be the other way round rich cold, leaner when up to temp?
I'll check the iat sensor values and do the wiggle thing on the other sensors.

 

This is what all the pistons were like when motor was stripped when it burnt a valve.