I suffered a couple of strandings on the way to work last week. The tach would go to zero while moving, and the engine stopped firing. It started, after delays of 1 hour and 5 minutes after the first 2 incidences.. but refused to start after the third time.

Once home, I found I wasn't getting any spark and, knowing that the ICM can be such a bugger, I bought (and installed) a new ICM. The car started right up - and I was happy. Then I saw that the ECM (ECU?) was giving me a code 15 (Ignition Output Signal).

I reset the ECM by removing the fuse for several minutes, but the code remained. Starting and running again didn't clear it up either.

Then it got worse! After a couple of minutes of idling nicely, I brought the RPM up to 2500 to warm it up.. that went well, too. As I reduced the throttle slowly, the engine speed jumped down to idle - then jumped back up to 2000, then down, then up. All this as I maintained throttle position steady. Taking my foot all the way off, it just idled - and, as before, it did it nicely. It seems that if I hold the throttle down enough to keep it over 2000 RPM or so, it behaves well... and if I leave it idle without any throttle, it behaves well there too.

Does anyone see a thread here? Do these symptoms point to something other than the ignition control module (igniter)? I cannot figure this out.

I have all sorts of guesses, but I'm hoping there's someone reading this who can say they've seen and cured this exact problem. Please, if you would be so kind, toss me a clue as quickly as you can manage, OK? I would really appreciate any help... I'm stressing having to rely on my car for work tomorrow morning. :(

Following up after a couple of hours...

I apparently didn't reset the ECM / ECU completely before. Since I can't find a fuse called "backup", except one under the dash as part of backup lights, and I have a fuse for each "ECM" and "Hazard" labeled in the box under the hood... I pulled all three and accomplished a reset which made it stop throwing the code 15.

I started it up again, and ran the engine speed up to 2250 after a minute of idling nicely. Coming back off the throttle it did the same thing - a wild drop to 1000 RPM then jump back to 2000 RPM - without changing my press on the throttle. After a couple of times, though, the swings got less until it wasn't swinging anymore.

Now, I clearly do not know the inner workings of the ECM... but it sure seemed to be doing something like "re-learning" after the reset. I exercised it for 15 minutes, just going to different engine speeds from idle to 3000, slowly or quickly raising and lowering the speed... and drove it 'round and 'round the block and it never acted up again.

I can't say I entirely trust the ol' lady, but I'm going to have to.

Do you have any explanation about my car's behavior? I would love to hear from you if you do! I'd like to continue to be a proud owner of a nearly-indestructible, great gas mileage Honda for years to come... but I'm no expert at odd problems that crop up.

Back in January txgreasemonkey gave me loads of help, leading me to information he and others had compiled - and I learned a lot while fixing my car. Thanks to you if you pass through this topic!

Thoughts:

. You did a good job of identifying the problem--definitely a bad ICM. Did you apply heat transfer silicone grease to the back of the new ICM, clean the terminals, and ensure the female connectors are tight?

. Disconnecting the negative battery cable for 10 seconds will also reset the ECM--do this to be safe. Remember, txdiygal, it's always best to disconnect the negative battery cable, before working on the ignition system.

. You likely won't have any more problems like you were experiencing. Personally, I would also replace the coil--Honda dealers normally replace both, for good reason, at the same time.

Thanks again tx!

Yes, I used a high quality thermal grease to join the ICM and heat sink base. I did pay attention to the connections - and they all seemed tight.

How does one effectively clean the female terminals? (you'll probably guess correctly that I didn't, though they sure looked decently clean).

Would you replace the coil just for good measure... or would you think the bad behavior may have compromised the coil? I certainly wouldn't disagree with you... I'd rather get a new coil in there. Honestly, I'm actually using a coil I pulled from a junkyard distributor. I didn't expect it to work, but after removing the charred remnants of a high-voltage failure the system obviously suffered, then buffing the secondary (hiding in that cylindrical hole) to shiny... the thing worked! It got me back on the road when I had no more money, not a penny. *sigh* I ain't makin' much now, but I'll be getting a new coil right soon. ;)

Thanks again, you're a gentleman and a scholar!

I use #240 grit abrassive cloth (Harbor Freight, No. 2717) to clean the male and female connectors. Steel wool or fine sandpaper will work. Afterwards, apply a light coating of dielectric grease.

Maintaining the ICM, coil, main relay, and ECM are crucial to like-new reliablility and performance on these cars. Since you use this car to get you to and from work on time, I would replace the coil--you don't want the car to let you down on the road again.