Dasauto

On the highway with the cruise set at 65, hot day 91 degrees. Felt a slight "stumble" and CE light comes on, flashes 3-4 times. Stop and pull codes:

P0300 Random/Multiple Cylinder Misfire Detected
P0301 Cylinder 1 Misfire Detected
P0302 Cylinder 2 Misfire Detected
P0303 Cylinder 3 Misfire Detected

I can't imagine that many coils had an issue at once. Was not in the boost at all either.

What do you guys think? Maybe CPS? Car is stock right now except for intake (2003 C32) and has 54K miles. Has been running great with no issues for almost 2 years now.

Calling my mechanic but would love to hear your thoughts. Thanks

loudandheard

Have you moved anything in the engine bay recently? I had a similar issue, but I forgot to reconnect a coil pack when I took them off.

A CPS usually will shut down the car and not allow it to start until it's cooled down a bit. Most of the time you will get a CEL for the CPS, but that's not always the case. Replacing the CPS would be cheap insurance, but it's better to pinpoint the problem before throwing money at repairs.

Are you able to clear CEL and does it come back when you drive it? Are you experiencing poor idle or an odd engine shake? Does the issue happen on hard acceleration or during normal driving?

It could be wires, plugs, coil packs, clogged cats, faulty 02 sensors, or extremely dirty air filters.

The weird thing is that the misfires all occurred on the same side of the engine. Maybe there's a break at the wires that connect to the coil packs.

Dasauto

Happened during normal driving, was driving like a granny. You can feel a slight stumble/shake and then the light comes on. I was able to clear the codes and it ran fine but then just before pulling in the driveway it did it again, same codes, about 25 miles later. I also find it strange that it's all one side of the engine. Going to check things out once it cools down to see if maybe my open air intake caused some connection issues on that side of the engine. Filters are clean but have gotten a pending O2 sensor code previously.

loudandheard

See if you have a leak from the valve covers, sometimes oil will leak in to the spark plugs and cause issues.

Dasauto

This could be it as I was about to re-seal the covers as there is some leaking.

loudandheard

I read that it could be a bad cat causing the issues. Check to see if the cat is good.

Dasauto

I read that too but have no idea how to check without having a cat removed.

ddtham

Usually if a cat is bad, you can hear it rattling when you hit it with a rubber mallet.

Dasauto

Update.........mechanic can't look at until early next week. Took it for a little drive yesterday and it seemed fine, then felt the stumble again and sure enough it threw the same codes but with one more this time:

P0134 O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)

So my question is, wonder if the 1-3 cylinder misfire caused this or did the 02 sensor cause the misfire? Egg before the chicken, chicken before the egg?

Lenin

More reasons to check your cats. Unlikely that the O2 sensor will cause misfires.