Engine Need Help Tracking A Rough Idle On 2003 V6, Not Iac Valve.

[F.D.K]

Need a second opinion on what the issue is. The car is a 2003 V6 mustang isn't anything fancy or have anything fancy on it. Spent last weekend trying to hunt down what I believed to be a vacuum leak. Turns out it wasnt a vaccum leak. Changed IACV after not being able to find any leaks. After that tested EGR valve and that seems to be working. The car itself when put in reverse shakes like high hell. It seems like it will rattle itself apart. Now when put in drive it accelerates decently with a little hesitation when the gears shift. Now once it slows down at a red light, the idle sits at 600rpms, now that's seems about right but it shakes in the brake and if you move it a tad forward the shake goes away. I was thinking something to do with the suspension but that wouldn't explain why I'm also only getting 188 miles per tank and that's highway. A little stumped, timing is right, good acceleration and no shaking when driving. Any ideas?

 

[General karthief]

Have you done a tune up lately, plugs, wires or coils?
Also check the engine/trans mounts.
Checking for codes may help also.

 

[wmburns]

Check out this recent post. The take away from this is how the motor and transmission mounts can affect how it runs.

https://www.stangnet.com/mustang-forums/threads/3-8l-vibration-engine-swap.901933/