Ever since I messed with my timing, when I crank my truck up it cranks and revs up to about 1200 rpms then drops to 500 and it does this about 3 or 4 times then when it finds an idle point it shakes at idle

 

As they say, "The devil is in the details"......

So what did you do when you "Messed with your timing"? Step by step, please.

 

500 rpm warm curb idle it too low. You don't care to share any info about your truck, engine or transmission type, so I cant tell you what it should be. But for a 302 w/ A/T it should be 650-675 rpm.

Suggest you remove, clean, then reinstall your IAC. Then test it per instructions on this link: http://www.fordfuelinjection.com/?p=39

Error code scan result's would prove helpful!

 

Did you remove the spout when you timed it?

 

Sorry I have a 94 f150 302 MAF with a 4r70w tranny. When I bumped the timing I unplugged the spout, marked my stock timing, loosened the distributor up, turned counter clockwise until I could see maybe a centimeter of clean metal then tightened it back up, cranked her up used the timing light to see the timing, killed the truck and put the spout back in. I had to put it back to stock timing using the same method and now when it cranks the idle bounces a couple times and then settles down

 

Clockwise. Not counter clockwise

 

What is your warm curb idle RPM????

Clean then test your IAC.

Read link: http://www.fordfuelinjection.com/?p=39

 

What is warm curb idle? And can someone please show me where the IAC is located?

 

Normal operating temp. Drivers side of air intake manifold, right after where the rubber intake air hoses boot.

 

A cylinder/tube looking thing bolted to the drivers side of the throttle body right behind where the intake hoses attach to the TB. I don't know how to check the idle without a tach though....so hopefully you have one.