rebuilding my '93 4.0

[exploder_dude]

im having some serious issues trying to get this thing running right
i had to replace the bottom end so i got a '98 motor. i know its a little different but it wasnt my idea
we got it all put together and this is what we got
'98 bottom end
'98 intake manifold that is ported and polished
'93 heads and everything else is '93 like all the wireing
when i start it up it idles very roughly and has very late throttle responce, it wont rev past 2000 rpm's and the engine will die from rough idle. the check engine light also comes on. theres either a major air leak or something doesnt match up with the computer and sensor stuff
does anybody know if i did something wrong or what it might be???

 

[exploder_dude]

ask questions if you need more info

 

[exploder_dude]

oh yea, and i have the '98 fuel injectors

 

[BrooklynBay]

Welcome to this forum! Check the intake manifold gaskets, and find out what the code numbers are.

 

[1Aauto]

welcome to the site

 

[exploder_dude]

i dont care about being new to the site. just help me out haha

 

[exploder_dude]

i replaced a few sensors and it runs now but not full power. its running lean and it miss fires or something once it passes 2,500 rpms

 

[Ronin8002]

well for one, 93 heads on a 98 won't work well together. The 98 pistons have a bigger dish in them than the 93 motor did. Since you kept the 93 heads (which have larger combustion chambers than the 98) you basically dropped your compression ratio down to 8:1 (stock is about 9:1)

You need to get heads from a 95 or later motor to get stock compression back.