[SkyKnight]

This is kinda hard to explain but here ya go....In the mornings when I start the car, it starts instantly as it has since new in 2006. Immediately after approx. 3-5 seconds, the engine strains and the valves chatter as if it is loaded severely. This actually started during the winter months although it seldom gets below 32 degrees down here in Houston. I took it to a dealer but I think they were just trying to sell me a car. My car has >180k miles. Later I've noticed as the weather warmed, the problem had gone away but recently returned a couple days ago. btw....this only happens after the has car sat overnight. After my 20 mile drive to work in the morning, it starts just fine the remainder of the day.

I suspect there is some kind of sensor failure happening; sort of like the old stuck choke plate in carbed engines back in the day. The straining only happens momentarily, like 1-2 seconds, not long enough to shut down the engine. The car otherwise runs and drives just fine. The dealer tried to convince me it is the timing chain since the car is old with high mileage. I think if it was a timing chain issue, I would be experiencing other power issues as well and and a constant occurrence. The check engine light is not illuminated either.

Hopefully somebody out there may have some info to help me out.

Much appreciated,
~alan

 

[RyanY]

I think the dealer may be correct, unfortunately. Around 117k my 07 started to chatter for a second or two on cold starts and then was fine the rest of the day. New chains and tensioners solved it.

 

[SkyKnight]

OK. Thank you. I will wait until the cold weather gets here. It happens every morning when it is cold outside which leads me to believe it is some kind of sensor that would change the fuel setting on cold starts. Since I wrote this post, I've been starting the car with veyr light pressure on the gas pedal causing it to rev a little over 1k rpm. Doing so seems to work.

 

[SkyKnight]

Well I have some good news! I think my problem was solved inadvertently. The straining problem has been plaguing me for quite some time to the point that I bought another car, an ATS Coupe. Well, as I mentioned in my initial post, this problem started in the winter. That is an apparent coincidence. I always change my oil and rotate the tires every year during my holiday break just for convenience. The repair shop I had been using for the past 3 years has been falling short on our service issues; on my other cars. I had been taking all 3 vehicles there but recent and consistent return visits caused me to seek a different service facility. Upon doing so, I requested my usual oil change and tire rotation at the new shop. As I pointed out, I do this annually regardless of mileage before I reach the expiration reminder notice. To much of my surprise, anticipation and preparation of the startup straining, it hasn't returned! It has been 1 1/2 months now and the car is its' old self again! Day or night, long or short intervals between operation, warm or cold, no more issues. In light of the other repair issues (not on this car) I had been dealing with from the other place, all I can surmise is the new facility is using the correct oil and maybe the other place was using the wrong type (other than Mobil 1). like i said earlier, I think the dealer was trying to sell me a car siting my complaint was consistent with service history of the 3.6 V-6 engine and mileage. A note on mileage, I am now at 206k. I thought it was odd they didn't give me a service report or summary for their diagnostics, just the service manager's verbal summary. Even the salesman I was working with was giving me the same theory of diagnosis. I also asked my original repair shop to diagnose the problem, even though I was growing unhappy with their service but was trying to still believe in them. They gave me the same theoretical diagnosis that the dealership did as if they possibly read a service bulletin.

Anyway, my best guess is the new shop is using the correct oil and the old shop was using something else. That is the only change made and the problem has gone away.

~alan
Once again happy CTS owner and new ATS owner!