Brain-damaged engine

(2/1/2014) In many ways, the Engine Control Module (ECM) is the brain of a modern Harley V-Twin motor. Unfortunately, it's a black box both conceptually and physically: you don't get to peak inside.  When it starts to fail, you have to replace it; there's no repairing it.

(The back side of my damaged ECM is shown in the photo at left.)

For the last year or so, I have had a problem with ignition dropouts. At first, the problem was only apparent during warmup at idle RPMs. However, in December, the engine would miss badly at random times and RPM levels. Then, a few weeks ago, the engine would jump all over the RPM range when warming up. It was weird watching the techometer needle jump around (and hearing the engine revving) from 800 RPM to 3200 RPM to 2000 RPM and so on, for no apparent reason. It looked like my bike had lost its mind.

And in a way, it did. About three weeks ago, I managed to ride it to Jockeys Cycles in Morrisville--located in Jimmy Winter's old place--where Kevin and Jim diagnosed the problem as a faulty ECM, and possibly a bad temperature sensor. After some investigation, we decided to replace both the stock Harley-Davidson (HD) ECM (part number 32852-06) and Power Commander III with a single Thunder Max Electronic Fuel Injection (EFI) control module (part number 309-340). This was the least expensive option ($485 in this case) yet offers a flexible solution. Thunder Max offers an "Auto-Tune" module that I can later attach to this EFI module to add more precision tuning features.

Quick aside: Let me tell you a little story about HD ECMs and Power Commanders. Nearly everyone who buys a Harley changes out the air kit, exhaust, cams, or pistons, or some combination of these within the first 1-5 years of purchasing the bike. In fact, I'd say a majority of new Harley owners change out the exhaust within the first few months of ownership. (Yes, this offers a great opportunity for the anti-Harley people out there to bash the product or the owners. That's a topic for another day.)

Anyway, when you make significant changes to air intake, ingition timing, or exhaust volume/pressure, you usually need to add a progammable device, such as the Power Commander, to make the needed adjustments to ignition timing and fuel-air mixtures. What I learned the hard way is that HD dealerships will not touch the Power Commander, even if you pay them to do performance work on your bike and the Power Commander affects that performance.

I purchased the Stage 2 Kit from HD for my Road King a bunch of years ago. The dealer tech replaced the stock ECM with an ECM designed for the new setup, especially for the new cams. However, what he did not do, was remove the Power Commander I had installed a few years earlier. Consequently, at certain RPMs, the engine would fail to smoothly ignite across both cylinders.

One day, I was sitting outside the dealership near Knoxville, Tennessee when an older fella came out and joined me. We got to chatting and he asked me where I was from. I mentioned I was from the Raleigh area and he mentioned Ray Price Harley-Davidson. I told him that's where I bought my bike and recently had spent $2500 on a Stage 2 upgrade.

He told me Ray Price's reputation for performance work was excellent. I told him that in general, the bike was running great. However, at some RPMs, it hesitated. We speculated on the cause and I suggested that maybe my Power Commander needed adjusting. He quickly responded, "You got a Power Commander on there with a Stage 2 Kit, and they included a new ECM? Take that damn thing off! It's the problem." He was quite right. After I took the Power Commander off, the bike ran great. The lesson here is that a Power Commander module can offer a convenient way to tweak your engine settings as needed for relatively minor changes. Know however, that the Power Commander can confuse the ECM if they're not compatible or programmed for each other.

Going back to the brain analogy, you could think of my Power Commander on the Road King as a second voice in the engine's head whispering to not send a spark now and then.     

Kevin (at Jockeys Cycles) also changed out the engine temperature sensor just to be on the safe side. I did manage a little riding today, which is great considering it's February 1, but not enough miles to be certain we've worked out all of the problems this engine has been having. From what I could tell, we're off to a good start.

As always, keep the shiny side up!

-The Long Rider