B16A swap into 91 CRX DX

[digicidal]

I just had a B16 (first gen from an SIR) swapped into my 91 Rex (which was a DX previously). Although not strictly part of the swap, at the time I upgraded I/H/E for aftermarket. The header is a DC Sports 4-1 version (more on this later).

Everything was running great for the first couple of weeks. Had it tuned and she purred like a kitten...

That was then, this is now. When the engine is cold everything is perfect (or as perfect as can be expected) engine is a little rough, but not anything out of the ordinary. The problem only occurs when the engine is all warmed up - and even then only part of the time. When I give it decent throttle - not full, but about half way on the accelerator in any gear (but much more noticible in higher gears since they're longer) the engine will shudder as if it's running WAY too lean... and the power will be less than half what it should be. If I stay on it - the problem 'rights' itself within 5-8 seconds and then the engine sound returns to normal and the pull is good until the next shift... then back to normal. If I just barely give it any gas and wait until I get a little higher in the gear (~4000RPM or so) and then open it up the problem very rarely occurs.

OK so that's it for the problem... now what to do about it. At the beginning of my post I mentioned that I put the DC Sports header on, well it only has 1 O2 bung instead of the 2 that came stock on the OBD0 B16's... I had this done at the time of the swap, so I haven't been able to determine where they spliced the wires yet (or if they did even). I'm thinking this is a problem with using a one-wire O2 sensor farther down the exhaust line (since not as hot as in the runners and it's not a heated O2 sensor like OBD1 uses). Is it possible that this is just a bad O2 sensor (has anyone run a spliced 1 wire O2 on B16/PW0 setup with no problems) or should I go ahead and custom set up a 4-wire O2 or am I completely off base.

 

[B16CRX]

if this is an OBD0 swap, you need to have 2 O2 sensros in. This question is asked daily all over the internet. Buy another O2 bung and have it put into your heder somewhere near the other one and wire it in. Your problem will be fixed.

EDIT: why didnt you just use the stock b16 header that has both O2 bungs in it already? It is a 4-2-1 header.

 

[digicidal]

Well the DC header was for two reasons, one was for the increased top end powerband since I have the Y1/LSD JDM tranny it stays at higher RPMs most of the time... the second was purely asthetic since even though I'm not building a true show car, I want it to be near-show as well as having plenty of go!

I realize the question has been asked before... I've spent 5 days pouring over about 100 posts in different locations - the problem is that none of them are truly conclusive and the only ones that really identify a solution point to swapping the one-wire O2 sensor for a 4-wire and running to a spliced connection and a resistor on the 12V line switched at the ignition.

So I'm assuming from your post that my diagnosis is indeed correct, and that the problem is with the ECU not getting correct O2 sensor signals? If I use two O2 sensors in 'perfect world' setup I would need to make sure that they are only getting readings from 1-3 and 2-4 cylinders which won't work on a 4-1 no matter how you do it. I guess another possibility is getting a Hondata programming to always run in open-loop mode thus eliminating the 'dead-zone' of the closed loop mode during low engine load. Has anyone done this?

I guess short-term I can keep resetting my ECU to dump the long-term closed loop logs... but that's not the fix I want. :unsure:

 

[B16CRX]

well yea, ideal location is at 1-3 and 2-4. But you have to work with what ya got. If I were you and I wanted it running right, I would just add another O2 bung to teh header and another O2 sensor. You kinda lost me on teh 4 wire setup. I was under the impression that this is for a OBD0 swap/ecu. 4 wire is on OBD1 setups.

Most of the time when people have both O2 sensors hooked up, they have them backwards (switch C8 and C16).

Sorry if I havent answered any of your questions...

 

[digicidal]

OK... thanks for the input... I'll see where I can tap for the second and since I've got to trace the wiring anyway to run the second I might try out the 4 wire solution too... since I can do it first. If I do and it works well I'll post pics and results... if not then thanks for answering so quickly.