My brother's lude idles rough and runs very rich. I pulled the codes but nothing. So I was searching online and i think that his map sensor is shot. When i test it there are 3 wires; 1 is ground which is good 12v, the other supplies 5v which is good too. The signal wire reads 3v with Key on Engine off but with engine idling -1v? i have read it should be less than 1v but i got negative (-1v)

 

All the negative means is that you got the leads backwards. It's basically 1v. The map sensor will normally only be bad if it throws a code.

If it's running rich you can seafoam it to see if it has an exhaust leak.

 

My ecu is chipped and the O2 is disabled. I just took a map sensor from the junk yard still no change.

 

it needs a full tune by a professional

 

we had it tuned already when we chipped the ecu last April. It was running great. It just happened few days back.

 

check for codes and post back what you find.
then do a valve lash adjustment, followed by a compression test

 

How long since plugs, cap, and rotor were replaced ?

 

plugs new. cap and rotor almost 2 years.

 

So you say you pulled the codes and nothing, does the check engine light work as it should, i.e. light up when the key is turned on, but go out once running? Did it come on at all while running? Might have to let it run for a bit to actually get the code to come up.

Until that is ironed out, follow what motoxxxman said, but I would add one more thing, check the timing belt, and ensure that the cams and crank are still in proper alignment. Easy to do while the Valve cover is off for the valve lash.

 

yes, that too, good idea