I have a 1995 Honda civic, dx, has the d16z6. Tuned on Hondata s200 P28 ECM. To make a really long story short I'll just say that I have been on this for almost a month now and I am still having the same problem. About 2 months ago I was just riding down the highway and my tachometer starting "jumping" anywhere from 3k to 7k. Didn't affect engine speed. A couple of weeks later I started feeling it miss and bucking like she was misfiring when the tach started jumping. And now, sitting in the garage if I start her, the RPM goes crazy almost immediately and sometimes won't hold idle and will let the car die. (That happened to me once in traffic.)

After much much testing and many frustrating days I have found that I am not getting suffice voltage to the ECM for the ICM. The pin number is A21 Red/Grn wire, 20 gage. I am only getting 6V there and should be getting atleast 10V. So I went to the fuse box under the dash, found a Red/Grn wire coming out of the connector that plugs into the fuse box. I did a continuity test on it and the Red/Grn going into the computer. I have continuity there on that wire BUT the wire has over 1k ohms. So i figure I'm losing half my voltage due to that wire. However, at the fuse box where the Red/Grn wire is, I have no voltage, if I back probe the ECM, I have 6V.

My main question here is what is supplying voltage to that Red/Grn wire.
Things I have had done:
Replaced distributor, external coil, ICM, Coil wire, Checked, cleaned and replaced ALL grounds. I have had the ECM professionally tested twice by two different people. I have tried running a straight 12V to the wire at the ECM and car will not start. I have done many many things on this car and I will be more than happy to explain further on any questions you may have. Thank you for your time in advance.

 

Maybe because it doesn't take straight 12v....look in the helms manual

 

Yeah thats why I was saying atleast 10V. Thats what repair manual calls for.

 

The igniter unit should get battery voltage on the Blk/Yel wire. What voltage do you measure there and at the same wire of the coil?

Also test the wire that pins to A21 for a short to ground.