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Flashing CEL question

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Mark R

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Any ideas what's going on here. On my way to work this morning, I suddenly got a flashing CEL having gone 100 yards down the road.

The car was running great. No misfires. Smooth as anything. Normal performance. Started right up.

Anyway. I stopped it as soon as safe to do so, and shut the car down. Started it up again and the CEL was gone, and the car was running fine.

I've checked for DTC using the OEM tool - no DTCs. No freeze frames. Misfire EWMAs at zero. CEL milage/time counter all at zero. Nada.

Car is an 06 Lexus IS250. 150k miles. Plugs changed 20k ago with the OEM iridium plugs.

Any ideas? Just a strange glitch?

I was always under the impression that a flashing CEL meant a serious misfire (e.g. a dead miss) but the car was running fine, with no ass-detectable misfire vibrations. Similarly, I always thought that if the CEL came on, that there should be a DTC. But in this case, zip.
 
A blinking engine light is usually a active misfire. Scan for codes and see what comes up. Maybe it was a one time thing. But be prepared to stop if it happens and the car runs badly.
 
Just had an employee with a P0303 code and a blinking CEL on a 2005 Mazda MPV with the Ford 3.0L V6.

Had 130K miles on the original back plugs...

Changed out the plugs and the problem disappeared. No codes.

A few days later, it starts stumbling, bucking, shaking, every once in a while after it warms up.

No codes at all. Occasionally bucking like a bronco.

Didn't think it was a misfire because there were no codes.

Well, it was a misfire of course. Took us a while to believe it.

It was cylinder #3 again. The coil this time. Changed it and it's been smooth ever since.

So, you can have a horrid misfire, without any indication from the ECU.
 
What were the outside conditions? A coolant sensor , O2 sensor, MAF, IAC, Knock Sensor, could have given it a reason to come on. Similar instance a month ago on my F150, a few days later it happened again but this time there was a code. Misfire on #5 COP.
 
We eliminated all of those other suspects. I didn't consider the coil because I believed that would surely report a code.

When we faced the inevitable, and recalled the original code, and checked for a bad #3 coil, it was obviously the coil. Whenever it got hot, it started acting up.

Apparently, Fords suspend misfire monitoring if the fuel level is low...below 15%.

They will also turn off the injector to the cylinder to protect the catalyst...which then inhibits the misfire code apparently.
 
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