ok... I have an 89 civic hatchback with a d16a6 swap in it. I have been trying to figure out why it has the check engine light only at high speeds (highway driving) and now I can explain what triggers it... but I can't figure out how to fix it... I guess when the car reaches over 1500 rpm and remains consistent speeds the car will kill injector flow a bit and then the car will signal code 1. I have already replaced the o2 sensor, the fuel pressure regulator, and the fuel filter... and still nothing changed. what do I do? This is really getting my goat. What am I doing wrong? It the idle bad? Did I miss something? What?!?

 

did you reset the ecu?

 

My car actually does this as well, but only with my chipped ECU. It doesn't do that with my stock PM6 ECU. If you have access to another ECU, give it a try and see if the problem still comes up.

 

pretty sure it's be your ecu. mine was the same thing but comes on when in high gear and braking to a lower speed. switched out ecu and runs great.

 

Some chipped obd1 ecu's have a feature that uses the check-engine light as a shift light. It can be set at any rpm to come on, maybe whovever set the base-map turned on the feature without your knowledge? Who knows, just a suggestion.

 

I am unaware if it is chipped but its a pm6 ecu. I will talk to my builder and see if he has another one. and I will let everyone know...