I have a 93 Civic DX hatch. I swapped in a B18c1(OBD2), converted to OBD1. I get CEL # 3 only at 70% throttle or higher. I also get #21 after the #3 code kicks in. I know what the codes are, but why do they only come on at a certain RPM or throttle posistion? I have tried different MAP sensors and still have this problem. When this happens I can simply turn the car off, then back on and codes are cleared and the car runs good again. Has anyone ever had this happen to them?

 

sorry refresh my memory, 3 is map i know that.. other is ?...

lets see what ecu u running.. most stock ecus can read up to 11psi i believe.. and u said ur running a stock gsr.. all vac.. maybe mapsensor no good.. try swapping with a good one and if its still coming on check for loose wires.

 

I am running a chipped P28. I have tried a stock P72 and a P28, a they do the same thing. I have tried 2 other map sensors and got the same results. The other code I listed is VTEC related. Yes, Vtec works then stops when the MAP sensor goes crazy. I know VTEC works by listening to the exaust sound and also my VAFC says it is working as well. The MAP goes to crap and then the VTEC disenguages and gives a CEL for that as well. I am just wondering why this is only happening under load. I can run 90 and then jump on it and get the code, turn the key off and back on and the car runs great. I also have noticed how rich the car then runs when I get the CEL and the ECU seems to be in a limp mode until I clear the codes by turning the car off. I am just about to buy a new MAP sensor and say screw it.

 

very interestin.. well first off yes a map sensor will throw the engine into limp mode.. this is usually to keep boost heads like myself under raps. this will make your car run just slightly rich and definately disable vtec. hwoever im pretty sure the vafc "says vtec is on" based on what rpm you have it set to.. not actually by detecting if its on because ive had instances where a motor with a vafc2 had the unit claim that vtec was on when limp mode was on and the car definatley wasn't hittin vtec.

you said you tried other map sensors? but still gonna try getting another map sensor?
u have an o ring on the map sensor? make sure its on there tight and the wires arent loose anywhere.

also your statement about vtec working by listening to the exhaust sound?
are you sure?