I have had my 03 for a few years now and ever since I got it (30k + miles ago) it always felt tired/lethargic. I used to have a 96 Sable with the same Duratec engine and it had much more pep. My 03 also will stutter/hestitate after a complete stop (60% to 70% of the time especially when warmed up). I am trying to figure out why.
Over the past 3-4 years I have:
1) Replaced the coils and spark plugs (good stuff I think OEM
2) Seviced the transmission in 2014 (guy said it was likely not a trans problem, but who knows).
3) Swapped the air filter and cleaned the MAF
4) Cleaned the IAC
5) Replaced the intake manifold gasket
6) Replaced the fuel filter
7) Kept up with maintence (oil/filter, brake changes)
8) Replaced the oil pan gasket
9) Added sea foam and fuel injector cleaner to the gas often (sometimes helped it a little, but only temporarily)
No check engine lights, just runs sluggish and studders. I am thinking it could be one of two things.
Maybe a vacuum leak (previous owner looked for one but could not find one). But I would think a vacuum would trigger a running lean check engine code. Also it does not idle poorly and has steady rpms
Or more likely it has bad fuel injectors, which I am considering replacing this week. On a side note it burns a good amount of oil so I hope it is not just dying. Just wanted to know what you all think, or if you had similar issues