Chassis - 2000 Civic Coupe Ex

Motor - B18b1 block, B18a1 head, p75 intake out of a 92, GSR throttle body

Distributor - OBD2 with new coil and igniter

EWH - stock d16y8 harness with CKF Bypass and AEM wideband sensor installed

ECU - S300



Been chasing my tail on this issue for over a year now. It won’t rev more than 2000-2500, seems to be running entirely too rich no matter how much I adjust the fuel on the ecu, although the AFR sensor shows leaned out. I recently bought new injectors and plugs, and after install, the car revved to 3500 and seemed great. I turned it off, ran some errands, and when I came back it would rev past 2000 again. I’m completely new with Hondata, I only got it because a buddy of mine that’s experienced was helping me out and said it should be an easy fix. He’s out of town for a few weeks and I’m getting ready for a big move out of state and I’m trying to get this thing running good before the move so I don’t have to sell it. I can provide any pictures, videos, or any information needed that could help in identifying the problem. I made a thread a year ago that Ive linked (https://honda-tech.com/forums/hybrid.../#post52812267). Appreciate any help I can get

Is your launch control function enabled ? If so, what is your launch RPM set at ? You show NO vehicle speed in your datalog from the video posted, which means that your S300 may believe that you are sitting still, and thus, your rev limit is essentially set to the launch RPM.

I actually am sitting still in the video. This issue was present on a stock ecu as well, I got the s300 to gain more control over the ecu to try and pinpoint the problem. The tune on it is essentially a stock p74 tune with slightly more fuel do to it reading leaned out, and an an increased iacv duty cycle.

Email me a like 2 minute log of driving the car and I can help you try to diagnose this. And send me the tune thats currently on it as well.

Audi.trevor@gmail.com

What fuel injectors do you have ? If they are the OBD-0 ones originally from the '92 Teg intake manifold, they will be low OHM injectors that do not work properly with your OBd-1 ECU... not to mention, if you didn't wire in an injector resistor box, you can damage the fuel injector drivers inside the ECU. Also, what fuel feed line are you using ? You MUST use a 1994-01 Integra fuel feed line (between the fuel filter and fuel rail inlet). A '90-93 fuel feed line may work, although it may require some slight modification. The original Civic fuel feed line will NOT work.

This is what I was thinking. Non-saturated obd0 injectors.

92 injectors are obd1.

Obd0 injectors are low impedance and could ruin the injector drivers in the Ecu if not ran with a resistor box. If they have a resistor box they will work just fine with a obd1 Ecu, I’ve never heard or seen obd0’s not work when properly coupled with a resistor box.

+2 on the fuel line though, some fuel lines feed the rail in on the end in which one end has a larger inner diameter opening to allow fuel flow, this coupled with the correct fuel rail washer, which looks like it has cogs on the inside allow fuel flow. The wrong washer / fuel line, can cause fuel pressure at idle to be fine but as soon as theres a demand for fuel flow it will drop pressure fast at the rail.

'92-93 Integra fuel injectors are actually low impedance OBD-0 injectors... this is why a resistor box is mounted near the clutch fluid reservoir on this chassis. Low impedance fuel injectors plus a resistor box creates about 10 OHM of resistance, whereas, OBD-1 high impedance fuel injectors are typically about 12.6 OHM... so they don't function exactly the same (not to mention that "peak-n-hold" injectors open faster than "saturated" injectors). Low impedance fuel injectors and a resistor box do NOT work perfectly in an OBD-1 ECU powered car... they will work OK unless properly tuned.

I stand corrected.

still his issue seems more like something along the lines of fuel feed line/ washer is blocking fuel flow essentially causing a physical rev limiter due to lack of fuel pressure at the rail. I don’t see low impedance injectors just cutting out at 2k and not responding to any inputs from attempts to make things work at the Ecu.

The greater the engine RPM, the greater the heat generated by the lack of resistance... and the fuel injector drivers inside the ECU shut down. This is a hit or miss prospect with OBD-1 ECU's... I have seen some overheat and shut down quickly and others run indefinitely.
I don't disagree with you on the fuel feed line washers and installation possibly being the cause... I have talked about this very issue on countless threads here.

Figured I’d pop in to say it did end up being the fuel feed line. I checked fuel pressure at the rail when I first put the motor together in 2024 and it was fine so I never thought to check it again. Ended up finding the issue about a week after this post when I bought some new oem injectors and it ran perfect for all of 30 seconds. Put a braided line on from Jackspania and fixed the issue entirely. She’s been running good since as a weekend driver and almost got 500 miles on the rebuild. Shout out for all the help.