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I bought this car (second 2003 GLX 2.8 [typo in title and can’t change] wagon) last year with 90k miles. It’s run well, but has been using oil. I just changed my oil last week and have heard a loud clunky sound twice when trying to start. It’s a horrible sound, but then the car starts easily the second try. My dad said this is because I’m starting on the compression stroke. Now the car is starting to idle rough. It’s always had an Evap code, but nothing else. Timing belt was changed at 80k and I’m just about to hit 100k. Wondering if I have bad rings...


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It seems like that thread refers to the codes, but nothing about the rough idle. That’s what I’m really concerned about. I’ve always had a check engine lights for Evap leaks and vacuum leaks. Never really concerned about that. But it definitely seems like the car is running rough right now.

My try throwing some seafoam in the engine to see if it helps.


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Vac leaks will cause a rough idle. Cleaning the throttle body will usually do a lot more than Seafoam. As for oil, make sure all of the leaks are repaired, if it's still a problem, the valve seals are more likely to be an issue than rings at that mileage. I did valve seals as part of a head rebuild at 92K and it drastically cut my oil usage on my V6.
 

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Vac leaks will cause a rough idle. Cleaning the throttle body will usually do a lot more than Seafoam. As for oil, make sure all of the leaks are repaired, if it's still a problem, the valve seals are more likely to be an issue than rings at that mileage. I did valve seals as part of a head rebuild at 92K and it drastically cut my oil usage on my V6.
Cool. I’ve got some throttle body cleaner and will give it a go. Any tips on telling of the valve seals need to be replaced?


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Unbolting the throttle body is the best way to clean it (it's also a pita). A good clean and working PCV might reduce some of the oil burning. I did not notice any symptoms from the valve seals, I burned oil on long highway trips (1L every 1000-1500mi). I suspect the cats burned it all off as there was no smoke or smell. In local driving, it might have burned 1L in 5K. I only had the heads rebuilt after a idler roller failed after 18months/22K. The oil burning on trips dropped to 1L per 3K or less and locally to .5L per 5K.
 

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rough idle could also be from leaking valve cover gaskets, and misfires because of it, but you would normally get codes for the misfires.

If its plowing through oil you could be losing oil via the VCGs, you could also be losing oil through camshaft / camshaft sensor seals.

Any tips on telling of the valve seals need to be replaced?
Check your spark plug tubes and see if there is any oil in there.

PCV "hoses" may also be clogged.
 
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