Why no Code?

2003 Mustang GT. Pronounced misfire. The ECU isn't throwing a code. I'm 95% certain it's a coil buy which one.

Why would there not be a code set?

Some ECUs seem to be very lenient with monitoring misfires. My 2002 WRX had s bad fuel injector and, even running soley on there cylinders, I struggled to get it to actually set a code.

I have said it before, I will say it again. Ford has the worst misfire detection in the automotive world. If it does set a code, it will be the wrong cylinder. A good scanner should let you watch the misfires counting up. Then you just need to decide whether its cylinder #2, or the second cylinder in the firing order.

Streetwiseguy wrote: I have said it before, I will say it again. Ford has the worst misfire detection in the automotive world. If it does set a code, it will be the wrong cylinder. A good scanner should let you watch the misfires counting up. Then you just need to decide whether its cylinder #2, or the second cylinder in the firing order.

Got to pile on here it really is terrible. On the Tbird I just replaced them all as it was basically impossible to find the exact one that was misbehaving. Full set is only about 79$ on Amazon.

In reply to wearymicrobe:

I just ordered a full set.

Interestingly enough, my 06 P71 will set a code instantly, and correctly. I kind of expected the Wife's Mustang to do the same.

I've noticed the misfire detection on my Jeep will pick up on minor misfires (especially at idle) pretty readily, but it takes a while to pick up on a dead miss.

Somewhere in my stuff I have a light that was used to check plug wires. Just put the tip on the wire. If it was good it would light. Wonder if it would work on coils. Seems like it should.

Toyman01 wrote: 2003 Mustang GT. Pronounced misfire. The ECU isn't throwing a code. I'm 95% certain it's a coil buy which one. Why would there not be a code set?

If you cleared the codes with a misfire present, the computer will have learned the misfire as normal behavior.

Happens ALL THE TIME. Especially on work vans with so much crud in the cabin that it's impossible to get the doghouse off.

I've just hooked a timing light to individual wires and aimed it at something to watch for spark.

In reply to Knurled:

I haven't cleared any codes, it just hasn't set them.

Mr Joshua, it's COP, so no wires to hook to.

my 2000 F250 did the same thing, when i first got it it had a CEL for a single cylinder misfire that i had never felt, replaced that coil anyways since i had some good used ones laying around. around a year later i had a intermittent misfire that was very noticeable when it was misfiring but it never gave a CEL, i drove it for a while waiting to see what cylinder it said the misfire was on but never got a code. It finally got to where it was a constant misfire all the time. After a little interweb searching i found that quite a few people say if you have multiple misfire/more then one coil bad then it wont usually give you a code. I ended up changing all my coils out with the good ones i had sitting around and it's been fine since.