Been getting misfires... now getting catalytic converter code p0420. I know that misfires will eventually cause the cat to get messy / clogged / melted, but what about the other way around?

I know my intercooler has been leaking for a while, could this have something to do with misfires?

Trying to diagnose the misfires. All new plugs. About to do spark plug wires next.

Thanks

 

What are the misfire codes? Is it on the same bank or random on both. I do recall at least one member (was it Jake form EC?) who had misfires due to clogged cats.
Regarding the leaking IC, I can see how this can mess up an injector and cause a misfires, but this is very unlikely for various reasons.

 

A misfire results in unburned fuel leaving your engine and igniting in the catalytic converter, causing it to run much hotter than designed disintegrating over time. Your misfires most likely caused the p0420 code, catalyst below efficiency code bank 1. Coincidentally, are your misfires also on bank 1 (cyl 1 through 4)?

 

Yes it can; I had exactly the same thing. I also had misfires under full load and high RPM (on cyl. 2 for some reason) and found out the intercooler was leaking. I replaced the intercooler but that didn’t solve it. Opening up the clogged cat did..

 

Thanks. That is my next step to open up the cat, remove the insides entirely and get it welded back up. Is that going to cause CEL or codes?

Here is some back story on some issues I been working on over the years... finally put together a bit of a summary.

So my 2002 C32 - 138K miles - jet is having some issues.




Couple issues - it idles oddly at stop lights and has for some time. Its just an annoying 'bobble' that should not be there. Have yet to put my finger in exactly what is causing it.




Recently changed the fuel filter. Changed the plugs. Tested the plug wires - all seem good.




I have used seafoam several times and never had any issues. I have used it to clean the engine internally prior to oil change and also probably 5 times or so in the gas tank. I also recently used the 'spray in the throttle body' method a full can of the stuff. Thinking if the injectors were jacked, this might help. Sprayed, let it sit 30 min - then hard run - lots of white smoke as expected but not tons. Quick burst and then done. Probably went half mile and turned around and completely gone by time back at my garage.




Thinking it could be a couple issues.




1 . Plugs - doubt it - changed them.
2 . Plug Wires - doubt it - tested all of them. Update - now have new OEM wires.
3 . Cats - ?? - not sure. Some say seafoam or other 'additive' cleaners will mess them up. How to test which one? - Update will pull the O2 Sensor on passenger side.
4 . Vacuum leak - need to research more on DIY method to do this and where to input the smoke....could be this and just not sure where to look. Have tried spraying starting fluid around the engine several times and locations... nothing really stood out.
5 . Injectors - not tested - suspicious this could be the issue - hence the bottles of seafoam... after 2 runs of seafoam in the tank... still bobbles. Still not sure on if I should pull them. Also not sure how a shop would test them. I called and got an estimate for like 150 bucks. They say they do it on the car. Not sure how that works but must be super easy for that little of money.
Update - elected not to do the cheap 'on the car' cleaning of the injectors.
6 . Coil packs - not tested

Video of bobble at idle. Hard to see - go to almost the end.





A bit hard to see the bobble. Sounds like a rickety mess in this video, does not usually sound that shaggy today (more on that below). I have commented over the years how clickety the engine has always sounded. The engine bobble at a stop light is enough to bug me, so much so that I put it in neutral on occasion to make it go away. Thinking is a easy fix and research will will the day.




Ticking 1 - 100K Miles..


Ticking 2 - standing beside car


Ticking 3 - relatively cold start


Ticking 4 - I thought part of the oil filter broke off... have now accepted that this is how it sounds... after much research here on the forum(s)


Ticking 5 - oh man... the clicking is brutal in this vid... haven't watched in a long time... 5 years ago.








Fast forward 5 years..

I did pull a bunch of gunk from my plenums. Not sure this is/was the bobble issue. Cleaned them out nicely and still have the bobble.

Still need to check my intercooler. Never wanted to get so far into a project where I could not drive the call for longer than a weekend. I still think the inter cooler has leaked over the years as I have had coolant loss when driving it hard and in hot temperatures. Have not had to add coolant in a long time, probably as I don't drive it as much and in my mind the leak may have sealed itself somehow given all the gunk in the plenums.




Video - Plenum Gunk





Now that you've seen that video, please comment and let me know if this is completely normal - it had 130K miles on it at the time that video was taken. Does all that crap 'confirm' that my super charger is leaking / has leaked... (pretty sure it does - I also have green mist in my intake area) or just that this is what an engine looks like when you pull the plenums after 130K miles having never cleaned them before.

Blinking Check Engine Light - Oct 2017

I get blinking check engine light now at WOT on freeway and have to pull over to reset the car. The engine stutters badly after I kick it and pop the check engine light. I have intentionally done this twice to replicate the problem consistently. Something is up. I know this because I researched 'blinking check engine light'. Bad bad, stop, serious engine issue.

So I checked EGR valve



Not sure if this is the issue. After inspection and hitting it with some brake clean, I do not believe this is the issue. I am curious if this is how they should look or if additional testing can be done on this one.


Here are the current codes - P0300 / P0301 / P0302 / P0303 -


For the "8 Ready' - I have no idea what those are. Is that past codes? I know what the codes mean... just not fully what the little code reader thing is telling me...

Also saw a video of changing the super charger oil. Should I do that? Did not know that you could / should. How many have done that? Stumbled on video on youtube - never seen it brought up here in the forum.

I now (Dec 2017) have new plugs, new wires, new air filter, new fuel filter and can pop the CEL at WOT with the P0300 / 01 / 02/ 03 at will. Just did that this morning. I saw another post where the CAM can get broken or otherwise need repair. Would a car even run with a broken CAM? My runs fine as long as I am not driving it super hard. I did a full WOT run this morning fine and then the second time, I got the blinking CEL with misfires 0-3.

 

I had same thing with no codes.....it was the coils...I checked the coils ohms and nothing showed inconsistent....but swapped them all, problem gone 149K miles on my C32

 

Thanks for this info. So... is my reasoning right that if I move the 3 passenger coils to the driver side. The issue should move with the coils correct? I just did that - cleared the codes - and then did a quick freeway run and instantly popped the CEL with a burst of WOT. It ran shaggy after (consistent on this point at least) that and I had to pull over and restart the car to get it back to running semi normal. Runs pretty good actually except when I make it do this.

I got back, checked the codes and same P0300 / P0303 / P0302 (which is what it was before). Is my logic wrong or does this rule out the Coils? I appreciate the inputs.

 

The gunk you see is dried up oil use a oil catch can that should take care of the problem and the green mist is coolant due to your leaking intercooler won' really hurt anything and it'l keep your valves clean.

 

Coils as in spark plug wires or coil packs?

 

The Coils......you can actually get them cheap on amazon....no issues with mine so far. or buy 1/2 and swap them til it goes away

 

Update: as described above - the problem did not move with the coil packs. Swapped the left three to the right side and vice versa. Codes stayed on bank 1 with 0302 / 0303 misfires. This makes me think clogged cats. Am I correct that the way to test this is to remove the O2 sensor which before the front cat on the side of bank 1 (Pistons 1/2/3)? Is this going to make the car super loud? Am I going to get new codes due to the missing O2 Sensor? And should I be able to make a few WOT runs and not pop the misfire codes? If so, this will confirm a bad bank 1 clogged front Cat yes? Want to be sure I am working the plan in the right way with the right expectations. Thanks for the info.

 

Maybe it is easier to try and have a look inside the CAT’s. They are probably melted down. If you have to empty them them you’ll have to find someone with STAR diagnosis who can program them out. Otherwise you’ll get codes.

 

Did you swap plug wires too?

 

 

Finally had time to get the cats off and look at them. Upstream one had completely disintegrated (I poured out a little pile of bits and dust) and effectively turned into what looked like a thick paper towel on the downstream cat. This 100% answers the question 'can a clogged cat 'cause' a misfire. Yes. She's back to running like a champ and looking great!

From the video.. 'Shouldn't there be more?' ;- ) . Yes, turns out it was all caked 'paper towel' style on the downstream cat. I'll call it a good run.. 147K miles... I'll take it.

 

Yes as a dealer tech for 20 years I have seen plugged cats cause a misfire. You can usually feel it struggling before it misfires. If you suspect the cats you could remove upstream 02's or loosen the cat connection at manifolds for test purposes to see if it improves.