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I am working on a 91 Civic DX hatch, 1.5 in our shop, a GM dealer. The tech working on it is somewhat familiar with the car but we cannot figure out what is going on.
First of all it has what seems to be the common code 16. Initially it would run bad on hard accel, but progressed to the point of stalling and then a very long drawn out starting procedure had to be done. The customer mentioned that sometimes cycling the ignition would get it to restart. We replaced the cap, rotor, wires and plugs, as well as the fuel filter before beginning the task of the 16 diag chart, all to no avail. Actually it seemed to run great, but if you stabbed the throttle to quickly it would bog down, backfire and die. It has good fuel pressure, but now it idles rough as well.
Anyway we went through the diag chart checking various things along the way until we were led to the replacement of the ECU, which I dont have a problem with if it fixes the car, obviously. My concern is that we arent sure it is going to fix it and I have found prices range from low 200's to 1000 dollars, and all have to be ordered, a little to much to guess with. Can anyone give me any advice, are there things we are missing, or is it to the point of ECU replacement and crossing our fingers? Any help appreciated.
Turns out it had a bad ignition igniter and coil, which is internal to the distributor, and an intermittant main relay.
I see this is an older thread, but I'll ask anyway. I'm also dealing with a code 16 on a 91 Civic, and was puzzled by the eventual solution to Dude911's problem. Code 16 indicates "fuel injector", so I'm wondering why the problem(s) ended up being elsewhere. Are these codes not as accurate as I'd wanted to believe?
My symptom is that after driving the car for 10 or 20 minutes, shutting it off, and then trying to restart it a few minutes later, it sometimes doesn't start. If I remove and replace the fuse to the ECU, the car starts right up.
The code 16 appears to be on basically all the time, though the car seems to run well (aside from the problem described). The only other problem I've noticed is some pinging at full throttle.
So I'm wondering if I should suspect the distributor and main relay, in addition to the normal suspects for an injector problem? Would these problems normally be fixed by removing the ECU fuse? Or does that cure point to a problem elsewhere?
. Clean the under-hood BACKUP fuse, going to the ECM, with #240 abrasive cloth. Also, remove and clean the 3-wire brass connector, going to the main ECM ground, on the thermostat housing.
. Perform the K-Test on the ECM:
The K-Test: Remove the MAP Sensor connector and turn the ignition switch to ON (not start). Using a multimeter, check for 5 volts going between the MAP Sensor connector's reference wire (+) and ground. As you look at the connector, this is the socket on the right. Really press the black test lead into the cleaned main ECM ground on the thermostat housing. If the voltage is low, it’s probably indicating ECM failure. Most failed ECMs will record a fraction of a volt. To me, the K-Test is simple, elegant, and accurate.
. Check all under-dash and under-hood fuses with a test light or multimeter:
. If the problem persists, start the engine, and, using a mechanic's stethoscope or large-handle screwdriver, listen for a clicking sound from each fuel injector. Turn the ignition switch off and disconnect the 2P connector from any fuel injector that does not click. Measure resistance between the 2 terminals of the fuel injector. Replace any fuel injector that doesn't measure 10-13 ohms. Should the problem still persist, replace the main relay.
Should the problem still persist, replace the main relay.
Thanks so much for the advice, txgreasemonkey -- and Merry Christmas to you, too!
After some searching, I found the factory manual for the dual point fuel injection system. Between that and your advice, I'm feeling pretty optimistic about solving this mystery.
As I'm going through the diagnostic steps, I notice that the resistance values for the injectors in the manual are a little different from the ones in your post. For the 88-91 dual point system, the manual calls for .6 to 1.6 ohms for the primary injector, and 6 to 10 ohms for the auxiliary injector. I guess it varies from year to year and model to model. I see the 88 to 91 multipoint system calls for a resistance of 1.5 to 2.5 ohms.
I follow the link and found all the helpful stuff you've posted about Honda maintenance -- what a wonderful resource! I'm forwarding the link to my mom's Honda mechanic, so he can maybe fix the idle fluctuations that have defied diagnosis for 15 years...
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