I'm having a problem with my 1990 CIVIC 1.5 STD. 3DR, Chassis: ED634, Engine: D15B1 and I'm hoping you guys can help.

It starts and runs fine when the engine is cold.
After five minutes it begins to run poorly, stalls and won't restart until it's cold again.
When it's warm, if I quickly press the accelerator to the floor, it is almost guaranteed to cough, hesitate and stall.

The ECU LED displays one short blink upon power up - O2 sensor.
I've replaced the O2 sensor (twice) with Bosch universal 1 wire sensors. It didn't fix the problem.
I've replace many other components including the distributor/exciter, injectors and on and on.
I reset the ECU and the one blink ECU error returns immediately.
I unplugged the O2 sensor (to force it into limp mode) and it still won't restart when hot.

I didn't think a bad O2 sensor would cause it to run so poorly.
Do these symptoms suggest something other than or in addition to the O2 sensor?
Should I swap the Bosch O2 sensor with an OEM Honda replacement?
Any other suggestions?

Thanks for helping.

 

Try unplugging the ECT sensor to see if the problem is eliminated.

Also try swapping in a known good ECU.

 

Thanks for the speedy response.

As you suggested, I disconnected the ECT, tried to start the cold engine. It cranked spiritedly but didn't give the slightest indication of running. I reconnected the ECT and the cold engine started right up and ran smoothly.

I checked the ECU for errors. It gave one short blink, pause, six rapid blinks, pause, six rapid blinks, pause, six rapid blinks, and so on. ECT fault.

This prompts a question about how to read the ECU LED errors. When I turn on the key there is always one short blink. Is that the ECU announcing it is awake or is it in fact an O2 error code as I've been reading it? With the ECT error code it was just blinking the six short ones repeatedly. It never repeated the one short blink. I thought it'd repeat all the error codes. I'm confused.

I have two spare ECUs. I'll try those next and see what happens.