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Problems and Codes After Changing Timing Belt

This is my very first car, a 2008 Chevy Aveo with about 100,000 miles on it.

My car is throwing a P0420 code (Catalyst System Low Efficeniency), and a P0340 code (Camshaft Position Sensor Malfunction) even after I changed the Camshaft Position Sensor.

These codes did not exist till after I changed the timing belt. About 1 week after changing out the timing belt, water pump, and all the various pulleys (which involved removing the cam gears) I had my first major problem. I was accelerating from a stop light and the engine just reved really hard, barely any acceleration. I pulled it off the road, restarted the engine, and limped it home. When I got it home and I tried to diagnosis the problem, the crankshaft pulley and the serpentine belt came flying off because I didn’t loctite the crankshaft pulley bolt. I replaced the camshaft sprocket and pulley and put it all back together properly this time.

The car was running great for about two weeks and then the acceleration problem came back, but this time it was drivable. The check engine light threw off two codes, a P0420 and a P0340. It did not want to accelerate at all, it would rev to the moon when I put my foot on the gas semi-hard and I had to just ease it up to highway speeds. On top of that, a sound of a belt rubbing coming from inside the timing belt cover appeared out of nowhere. When I took the cover off I saw that the belt was eaten through in the middle of the belt.

I took everything apart again, slapped on a new belt, changed the camshaft position sensor, and it was running great for about 2-3 weeks even with the P0420 code and the P0340 code going off. Now today its struggling to accelerate again and the belt is perfectly fine.

Anyone have any ideas where I could’ve went wrong? Could it possibly be something unrelated to the timing?

Thank you for any help you can give me!

The crankshaft bolt locks the crankshaft pulley and the crankshaft timing belt sprocket in place. Because the crankshaft pulley was loose you should examine the timing belt sprocket on the crankshaft. The sprocket, the key or the crankshaft may have been damaged when the crank pulley was loose.

You said you replaced the various pulleys… did that include the tensioner pulley? Failure on that side of the timing belt just screams failed tensioner pulley to me. That could throw a P0420 code as can a loose crank pulley.

This sounds like clutch slippage.

Thank you for all the replies

@Nevada_545 I did indeed have to replace the crankshaft sprocket and pulley, it completely destroyed the key on the crank sprocket and the indention on the pulley. If the sprocket and the pulley weren’t connected tightly with the key could this be the cause of my problem? I don’t have air tools so I couldn’t get that bolt as tight as it was when I first removed it. Maybe it had enough wiggle room to wear down the key again?

@Mustangman I did replace the tensioner pulley, but as I went to look at everything today the timing belt was way over tensioned. I’m definitely going to order another tensioner pulley.

@insightful That was the first thing I thought too man, but every time I’ve changed my timing belt it magical starts working again. After I changed my timing belt this last time it was running smooth, perfect idle, I could accelerate hard when I needed to merge, but after about two weeks it started idling poorly and lost a lot of power.

You need to replace more than just the tensioner pulley

You need to replace the entire tensioner

Did you put blue loctite on the crankshaft bolt . . . ?

You really need to torque those bolts down . . . hand tight is not nearly enough

another thing to consider . . . on some applications, you are NOT supposed to reuse the crankshaft pulley bolts. On some GM models, to be specific, you MUST replace the bolts, as per the factory service manual. Perhaps this applies to your engine, although I believe your engine is Korean

Key on crank is Mush? Hmm, crank and sprocket might not be in sync. Nothing a new crank won’t fix.

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Well, if this destroyed the keyway in the crankshaft as you mentioned then you’re in big trouble.

Your options would be to weld the balancer in place or replace the crankshaft with the former pretty much ending the thought of ever tearing into it again and the latter being an expensive repair.