Ghost in the machine
From time to time there will come my way a car that has a no start condition. That by itself is not unusual. What is unusual is the dead car with no code. Car computers are getting pretty good at figuring out what is going wrong with an engine and alerting the driver by setting a code. When this 2002 Hyundai Elantra showed up at my door with an engine that would stay running for 15 minutes and then die, my first thought was to look at the codes. There was a code for an malfunctioning MAP but nothing else.
Hmmmmmm. Something didn't seem right about that. Normally a malfunctioning MAP wouldn't lead to the engine dying every 15 minutes. Did I mention that it would start up again when the engine cooled? No? Well it would.
Replacing the MAP, I sent my customer on their way. They called back about 20 minutes later. Engine died. So, back it came.
Not having any codes to go by, I did my homework, Zen style (trying to relax), and discovered about 40 things that cause a car to die. Not helpful. However, using the Sherlock Holmes method, that being the most obvious solution is usually the correct one, I decided to inspect the crankshaft sensor.
Crankshaft sensors have a bad habit of cracking and yet still working. Not having a scope to check the wave form of the sensor, I just removed it. Here's what I found:
As you can see, the casing is cracked. Oil was seeping into the electrical contacts from the engine block. When the sensor was hot, it would stop working. Cooling down, it would start working again. I had found my ghost. So why didn't it set a code for a bad crankshaft sensor? My online homework did not discover the answer to that question, but 90% of the time it doesn't set a code.
This is why the Zen meditation method of engine repair is so necessary. It's this kind of thing that will push your already fragile mind over the edge of sanity. Unless you have a wave form tool, you will be going crazy trying to find a misfiring or dead engine caused by a bad crankshaft sensor. Remember also the Sherlock Holmes method. Most obvious causes should be checked before ripping apart the wiring to whatever particular "piece" you happen to be working on.
Cheers
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