My friends '96 Civic HX 5spd is getting poor mileage, the best is 33mpg highway. We hooked up an OBD 2 scanner and the timing is around 12-12.5 at idle and then when driving at light throttle it goes to a max of maybe 20-24 and as soon as you go WOT it will drop to 5 degrees or lower?? Obviously this is not right, it should be getting close to 20* advance even at WOT I would think. I noticed the front o2 is not cycling either, it is staying at around .600 volts and it is in closed loop so it should be cycling at PT but it is not. NO CEL light is on! Would the o2 be causing the messed up timing? I can't see what else it could be? The coolant temp is working correct, IAT is correct, maybe MAP?

 

Anyone?

 

keep in mind that on a HX the O2 is not read like a normal O2. It's a wideband, so the scanner may not be able to show what's going on with it.

where in the RPM range did you do the WOT ignition read? At lower RPMs 5* may be right...


it's also possible that the O2 is on it's way out, meaning not quite bad enough to set the CEL, but bad enough to be screwing with everything.
The HX (and VX) highly rely on the O2, when it's in question the car runs like crap.