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Discussion Starter #1
I bought my 08 g8 v6 in October and it ended up needing timing chains so I had my uncle replace the chains with a cloyes kit I bought. A few days after getting them changed the p0420 code popped up and my car runs sluggish on the freeway. Is it possible the timing chain could be a tooth off? It has a slightly rough idle and accelerates good 1-40 mph but after 40 it acts very sluggish. It was running rich but I changed my spark plugs and injectors and it stopped the running rich issue. If the engine is cold it accelerates great too until it gets warmed up. Should I order a new cat? The car has 129,000 miles on it.
 

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It's possible something could have occurred or was omitted as a result of the timing chain repair causing the p0420 code. Bear in mind, the timing (no pun intended) of the repair and code could merely be coincidental. A technician with the proper tools can verify whether the timing chain(s) are off a tooth or not. Were all three timing chains replaced? Wouldn't purchase another catalytic converter until the old one is verified to be defective. If in doubt, unbolt the old converter and examine it internally. open vesus closed loop
 

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Discussion Starter #3
I took it out back in December and it wasn’t crumbled or anything on the inside. Just looked dirty. I’m not getting any p0008 code or camshaft codes like I was before I had the timing chains replaced
 

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How many threads are you going to start about the same issue?
 

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Hmmm. seems like this is the third - maybe it will be a charm for ya.
183632
 

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Discussion Starter #9
I’m really just trying to figure out what’s going on with my car. If you aren’t trying to help out then please just go about your day. I’m trying to figure out if it’s maybe the chain or the cat
 

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Discussion Starter #10
I didn’t have the p0420 before the timing chain replacement is what throws me off. Just the p0008 code
 

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Discussion Starter #11
One of the other threads I made was trying to figure out why it was running rich too and the oil smelled like gas. I fixed that issue and it no longer smells like gas. Now I just gotta figure out the p0420 code
 

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For what it's worth, if a timing chain(s) were indeed off a tooth, there should be additional codes set correlating to the chains, camshaft, etc. Suggest fixing the exhaust leak mentioned in another thread and going from there. Bear in mind, if a chain has skipped a tooth, it will run like crap or at least be sluggish whether the vehicle is hot or cold. The car won't accelerate great when cold, then suddenly "discover" it's off a tooth once warm/hot and run like crap.
 

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Discussion Starter #13
Okay. That’s what I thought too. I figured it would throw a camshaft code or something if it was the chain. I’m gonna fix the leak and if that don’t work I’m gonna put a new cat on it
 

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Inspect (unbolt) the catalytic converter prior to replacing because it may or may not be part of problem and isn't an inexpensive (oem) part.
 

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How long did you drive it before replacing the timing chains. The P0420 code can take a while to set, so if you bought it and replaced the chains a week later the previous owner may have cleared the code and it just took that long to show up.

p0420 is a cat efficiency code. It's pretty straight forward that the cat is not performing up to the level the ecm expects it to.
 

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Discussion Starter #16
I literally drove it for a week before replacing the chains but when I clear the P0420 code it comes back within 15-30 miles of driving. Who knows how long the previous owner drove it while needing chains
 

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If you haven't already done so, Google P0420 as there are numerous reasons that will trigger the code.
 

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Discussion Starter #18
I have googled it and timing chain was one of the reasons on some sites so that’s what sketched me out a little bit. But I’ve replaced the maf sensor and the 02 sensors and I changed spark plugs and injectors already so my last thing is I just gotta replace the cat and see if that was the problem the whole time
 

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I bought my 08 g8 v6 in October and it ended up needing timing chains so I had my uncle replace the chains with a cloyes kit I bought. A few days after getting them changed the p0420 code popped up and my car runs sluggish on the freeway. Is it possible the timing chain could be a tooth off? It has a slightly rough idle and accelerates good 1-40 mph but after 40 it acts very sluggish. It was running rich but I changed my spark plugs and injectors and it stopped the running rich issue. If the engine is cold it accelerates great too until it gets warmed up. Should I order a new cat? The car has 129,000 miles on it.
When your uncle installed the new timing chains; did he make sure that all chains and cam shaft are all moving perfect sink? There is a special tool that GM has to make sure that is happening. If that isn’t done you will continue to have a P0420 code come up and it will effect your transmission as well as timing on spark plugs, etc. plus just FYI the V6 base G8’s are notorious for timing chain issues.
 

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Discussion Starter #20
I’m not sure if he did or not. That would make the p0420 code pop up and not a camshaft code?
 
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