Which came first - the misfire or bad catalytic converter?

I have a 2011 Chevrolet Traverse that has been out of commission since August 25th. It stranded me and my children 3 separate times this summer. The first time the vehicle overheated and we promptly had it towed and replaced the water pump. The second time the car was shuddering and would then shut off completely, check engine light was flashing. I was driving to my children’s school, which is less than 5 miles away, and was maybe half way there. I stopped as soon as I could and waited for a ride. My dad was able to drive it back to my house, which was maybe a mile away and we parked it. We had our friendly neighborhood mechanic take a look at it, reset the computer, and replace the coils, spark plugs and gasket. Check engine light went off. Dad, husband, mechanic all drove it for a short distance and said it was fine - I thought I was crazy. I then drove it one more time, maybe 5 miles. Check engine light came on, shuddering, loss of power, and it died. Gas smell. Had to tow it home and then to the dealership. We know it was misfiring on cylinders 1, 3 and 5 (I don’t know the exact codes, but those were the codes it was throwing). But we also now know that the catalytic converter was shot, clogged (once the dealership looked at it). My engine has been pronounced dead at 5 years and 68,000 miles. GM won’t cover it because the warranty expired in February. However, the cat was still under warranty and recently replaced, but of course that doesn’t fix a ruined engine. So now we are trying to determine which came first - the bad cat or the misfiring in the engine? If the bad cat caused the misfiring and ruined the engine, then we can get GM to cover it. But if the misfiring destroyed the cat, it’s now on us. $2000 to pull apart the engine and find out. Do I gamble? I pay the $2000 if the engine was bad, GM covers it if it was the cat. What’s the likelihood I come out on top? In addition, it’s a $7500 new engine, and if GM won’t cover, would you pay to put a new engine in it, or sell to the highest bidder. Mechanic already said he’d pay $4000, but still owe more than that on the loan. HELP!

Sell to highest bidder ? I think the 4000.00 offer is the highest bidder. Only you can decide how much to spend. My choice given the history of this thing I would bail because if you fix it anything else goes wrong will just annoy you that much more. Did you purchase this new ?

Agree! Cut your losses and bail. It’s like a bad marriage.

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I am the second owner, bought it in April 2012. I’m a stay at home mom, so I put very little wear and tear on it. Change the oil on time, etc. I can’t believe the engine is bad! My husband and I were trying to pay off our cars and drive them for another 5 years minimum. Really ticked that this seems to be a problem in a lot of 2011 Traverses and I may have to swallow it.

I would bet that the whole series of problems was caused by the initial overheating episode. This, in turn, may have caused one or both cylinder heads to crack or at least warp causing the misfire which then caused the catalytic converter to go bad. When the check engine is in flashing mode you need to shut the engine down immediately.

If you’re lucky the damage may be limited to the cylinder head(s) which can be machined if just warped or replaced if cracked. This would cost a lot less than replacing the whole engine.

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I agree with this. The bad cat was probably the last thing to go in this long line of failures and was caused by being overloaded with unburned fuel from the misfiring.

Take it to an independent shop you know is good and see if they can save this for less money. It is sad to see such a new car get dumped but this might be a money pit too. Maybe it wasn’t treated right by the previous owner or you got a bad one from the start. Also, the overheating might have done it in.

Definitely have it evaluated to see if it is just the heads. I am not aware of the firing order on this engine but are all the bad cylinders on one cylinder bank? It may only need a single head if so.

When it initially overheated I was in a drive thru line I couldn’t get out of, so I turned the car off and waited for the cars in front of me to move. The check engine light hadn’t come on before it started smoking. I immediately pulled it into a parking space and had it towed to the dealership, so I didn’t run it overheated or with the check engine light on.

What I’m pondering now is whether or not I have the dealership tear the engine down for $2000 to determine cause. I may have to eat that cost plus whatever repair/engine cost to fix it. If the catalytic converter didn’t cause the damage, which its sounding like it may not have, GM isn’t going to help. Its too young of a car for me to sink this much money into. Thanks for your 2 Cents :slight_smile:

Yes - 1, 3 and 5 are all in the front I believe.

I suppose I want a magic crystal ball for a mechanic. Can you give me a good idea ahead of time (before breaking the engine down for $2000), are we looking at something that’s going to cost $1000 to fix or the cost of replacing the whole engine?

I’ve always really liked my car - I really don’t want to dump it, but I can’t afford an unreliable money pit. :frowning:

I’d find a good independent mechanic. Dealers are notoriously expensive on this kind of repair. Check the mechanics files on this site.

Well in answer to the question, the misfire caused the cat to fail IMHO. I ruined mine after about 10 minutes in the garage with a misfire. $700 but the dealer covered it under warranty.

I don’t believe the bad cat would cause an engine problem so there is some other issue with the engine that others had said. Yep could sure be due to the overheating or whatever originally caused the overheating-may not have been the water pump but an internal engine problem. At any rate, I think I agree to just dump it and start over without putting thousands more into.

Look at it this way. You’re going to have to trade at some point so the timeline is just accelerated a little bit but save yourself the aggravation.

Misfire most likely killed the cat. And 1,3,5 are on the rear bank. If it were mine I would find a good used engine and find an independent shop to install it.

I had a Chevrolet Traverse as a rental when we made a trip through California about 2011 and I can see why you like the car. I would be tempted to go with a new engine seeing as how you still owe money on the car. I had a similar experience with a 1990 Ford Aerostar that I bought in 1991. Fortunately for me, it came with the balance of the warranty. I had some problems and the head gaskets were replaced under warranty. The engine still didn’t seem right. I was going to trade it in, but things really went bad before I got it traded. It turned out that the engine had a crack in one of the cylinder heads. Ford determined that enough coolant had leaked into one of the cylinders to score the cylinder wall. The entire engine was replaced and.I drove the car another 120,000 and it was still going strong when I traded it. My suggestion is.to fix the Traverse correctly with a new engine or dump the car and start over.


Concur, most likely the overheating caused the misfire which caused the cat problem. No way to know for certain over the internet of course, but that’s my best guess.

Agree…see if they will replace free first then go to a place that’s not all about production in the service department.Ethanol burns better at 210 .Engines after 2000 burn at that temp prior to that it was around 180.This is the reason for most catalytic converter problems for vehicles prior to 2000 or so.

There’s no way to prove your case or even theorize once the codes are erased and maybe not even with uncleared codes. That statement is kind of ignorant but some cars are just not going to allow repairs. The only way to find out is to spend and spend again. I would recommend doing the repairs but then you end up finding the blown head gasket and a damaged crankshaft. There is always some other bad luck lurking in the weeds.