[TheOperator]

[2008 CTS 3.6 DI] Engine light is on code P0017. Could just be a sensor issue, but I know this code can also relate to an issue in the crank/cam or timing chain and tensioner. I have been noticing a whooping/thumping noise when starting the car cold. It will happen about ten seconds after the car starts and only a couple of times (thump thump, pause, thump thump) and then the sound goes away and will not happen if the car is being restarted soon after it was turned off. Is this sound related to the check engine light or something else entirely?

 

[Joseph Upson]

That noise is most likely reversion (combustion gasses popping back into the intake. Premium fuel should make it stop, or not with the code. The direct injected 3.6L is sensitive to fueling and ignition/timing irregularities, which can be influenced by dirty intake valves.

 

[TheOperator]

That noise is most likely reversion (combustion gasses popping back into the intake. Premium fuel should make it stop, or not with the code. The direct injected 3.6L is sensitive to fueling and ignition/timing irregularities, which can be influenced by dirty intake valves.

Thanks, I will try that.

 

[Nonsmiley]

Most likely this is a timing chain issue.

 

[NorthernSRX]

Most likely this is a timing chain issue.

This was my supposition as well. That being said, Mr. Upson knows his way around the timing chains on these cars and I don't know of a timing chain condition on these cars that has them making whoopie.

 

[Joseph Upson]

Most likely this is a timing chain issue.

It's a contributor as it results in irregular timing consistency, but it (noise) can be present with old and new timing components and responds best in my experience to premium fuel and intake valve cleaning.

When GM was having trouble with these motors running out of oil because of long oil change intervals and forgetting to remind owners that the oil life monitor has nothing to do with the oil level and that it needed to be checked regularly, the affected cars would show up at the dealer running poorly and throwing cam codes along with others, because insufficient oil supply results in erratic cam angles. The OP hasn't clarified it, but the noise is very characteristic of the DI motor and the associated sensitivities. One in particular is the fact that DI motors don't handle rich fuel conditions well, which can cause the symptom experienced here. Cold startup is probably the richest condition the motor experiences under normal circumstances and that's one of the reasons the noise is usually only encountered during the first start of the day if it's cool.

 

[Lifespeed]

Mileage on the engine would be a pretty good indicator of chain life remaining, too bad the OP didn't mention this detail.

 

[TheOperator]

Mileage on the engine would be a pretty good indicator of chain life remaining, too bad the OP didn't mention this detail.

The car has about 120000 on it, I'm not sure if the timing chain is original or if it has been replaced as I'm not the original owner.

 

[NorthernSRX]

The car has about 120000 on it, I'm not sure if the timing chain is original or if it has been replaced as I'm not the original owner.

You should assume that they weren't changed. Trouble starts to pop up with the chains when these cars hit 100k miles - they just get worn. It's avoidable but barely.

 

[Lifespeed]

The car has about 120000 on it, I'm not sure if the timing chain is original or if it has been replaced as I'm not the original owner.

Absent documentation, you can be sure the previous owner hasn't replaced anything. While I'm not suggesting you don't consider all possibilities, the likely answer to a timing chain code is . . . worn timing chains. At 120K miles you're due for some maintenance, as you would be for any make of car with that mileage. Fortunately the CTS is a worthwhile car. Likely you'll need timing chains, water pump, shocks, control arms, motor mounts, alternator and eventually a driveshaft. Not necessarily in that order.