Hey guys. Got a somewhat strange question. A buddy of mine wants help fixing his car (Mazda 6) which currently has a flashing CEL (so, misfire). He thinks it is a bad coil because it happened to him last year as well. Basically, I am trying to get him to do some of the legwork like get codes and parts before I bring my wrenches over to pull his ignition off, but he is worried about driving with a misfire.

I was pretty sure that a misfire, especially due to dropped sparks, really isn't that big of a deal other than making your car run rough, but I just wanted to make sure. Worst comes to worst he may just foul a plug or an O2 sensor, right?

 

For the most part, yeah. A misfire can cause the engine to run rich, and foul things.
If he gets the codes read and has a cylinder specific misfire, have him trade coils (providing he has multiples) with that cylinder and another one, then see if the error code follows the coil or not.

 

That is a good call as well. I have been on him to do this. He isnt very tech savvy and thinks that I can wave a magic wand at his car and make it run right again. "So we can fix it tomorrow?" no..... you still don't know what cylinder its in. I'm not pulling your whole engine apart just to track down a misfire haha.


thanks

 

Driving a car with a miss is very hard on the Cat and the O2 sensor.

In school they told us not to drive cars with misses because if two plug wires were cross firing it could damage the motor. I have never seen that happen in the real world and I can not remember another mechainc talking seeing it.

 

thats if it has plug wires, which most cars dont anymore. depending on the year, the engine can cut out the injector to that cylinder to prevent further damage