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Discussion Starter #1
Okay, its a '93 T-bird with the 3.8 V6. As my title implies, it has a rough idle/shake to it especially at lower rpms. It has never been a smooth car, but it has gotten worse over time.

What I replaced:

-Plugs & wires
-IAC Valve
-PCV valve
-Vacuum lines
- Distributor cap & Rotor
- Fuel Filter
- Fuel Pressure Regulator
-MAF sensor clean

That's all the relevant parts that come to mind right now.

Other Information:

- Run 93 Octane
- Change oil regularly
- No CEL
- Got a code 558 (KOEO) for "EGR Vacuum Circuit Failure"
- Has been dying at idle sometimes, but can this EGR issue really be messing it up like this? I have replaced so much, and it hasn't responded too much to my work. I have yet to find someone who can figure this out, unfortunately. So, does anyone have/know of this? I have no problem fixing this, but id rather not if it doesnt help like everything else. Any and all thoughts appreciated



1,181 Posts
Well I know if the EGR valve gets stuck open it will cause an " internal " vacuum leak and the engine will act the way you are describing . It happened to my wifes Saturn so i pulled it and cleaned with carb cleaner while moving the valve with a small screwdriver and it ran just fine.
You could always make a temperary block off plate just to see if it smoothes out.
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