Car is an 04 MT, 91,000 km, original coils (!!) but on 2nd set of plugs. Has always run well, rain or shine, snow or sleet.

A month ago I was doing my morning redline when I got a flashing CEL. There did not seem to be any weird sounds or obvious power loss. After that, though, I noticed that the car took a long time to start, failing to catch several times before firing. It never failed to start, though.

Also, I noticed that at low rpm's (below 3000) there was a serious loss of power, with the car seeming to stumble and the engine note was louder and had a rough undertone. It seemed to run OK at higher rpm's, charging up to the beep almost like normal (perhaps louder, though). At this point, I figured the ignition was to blame and since I was due/overdue for this service anyways I ordered plugs/wires/coils. Unfortunately they took FOREVER to arrive and although I basically parked the car I ended up driving maybe 500 km before the components arrived and could be installed.

The car now starts and runs perfectly, but I am concerned that I might have some carbon build-up or that the cat might be compromised.

I know there is probably not much I can do at this point but hope and wait, but if anyone has some insight I'd appreciate it.

 

Hard to say about the cat... I guess if you don't find any of the common cat failure symptoms (power loss, not sure what else), then it's fine? For carbon, easy fix, run SeaFoam through it.

 

SeaFoam...had never heard of it but sounds like a plan. Thanks!

There are no cat symptoms to speak of...no CEL, no rotten egg smell, no power loss at high rpm.

 

if its driving normal, I dont think theres problem
a good way to tell is a dyno.

 

If you were going to spend money, then I'd say a compression test, not dyno.

You can take a look at the CAT yourself, it's only a couple of bolts and you can move it to the side just enough to take a look with a flashlight. Long as it looks okay and you don't suffer any other symptoms, you're probably okay.
Some seafoam can't hurt though.

 

do bad coils or bad plugs make a funny noise or something? jw since u stated u did not have a noise.

since ur running close to the warranty id try a compression test.