New here: ) rough idling problem

Ok so 1st off I have an 88' XJ, 4.0L 5 speed 4x4.
I originally removed the intake and exhaust manifolds to replace the 2 freeze plugs which are located behind them. After I put everything back together (including new intake/exhaust gasket) My Jeep idles really rough, increase the RPM's and it smooths out but there is still a slight miss even at high RPM's. It it running REALLY rich, dumping alot of fuel and because of this there is slight black smoke coming from the exhaust. I have replaced the intake/exhaust manifold gasket twice now and triple checked everything to make sure it is torqued properly. I've replaced the EGR valve and every vacuum line on the engine is now brand new, new cap and rotor button, new spark plugs and wires, and new fuel filter. Does anyone know of anyway to check for a certain sensor? I dont really want to drop the $ to replace the MAP, Coolant temp, and 02 sensors all together when it may only be one, or may not be those at all, any ideas folks? Thanks for any help in advance!

IAC is my first guess. Try cleaning it up
Maybe a TPS?
Both of those would vary your fuel

IAC will not cause rich running. It only affects idle speed.
TPS will not cause a rich condition either.
An overly rich mixture is caused by MAP, CTS, and IAT. In that order. My money is on the fact that the hose from the throttle body to the MAP sensor is cracked, melted, or somehow or another messed up as a result of being disturbed in the repair process.

Search how to test your O2 sensor and test it to identify or eliminate it as a problem. You can get an analog MM from radio shack fairly cheap.

If you have an intake or exhaust leak up stream of the O2 sensor it may be signaling a rich mix.

Check the exhaust downpipe doughnut seal.

1. What injectors are you running? Original OEM? Read this: http://www.jpmagazine.com/techarticles/engine/154_0811_preventing_jeep_engine_fires/

2. Injector 0-rings; cap; rotor; spark plugs; ignition wires; distributor pickup full of carbon dust from old cap & rotors.

You can check coolant and IAT sensors with an ohmmeter. They should not measure meg ohms or open circuit. Readings should be a few k ohms cold and hot reading in the hundreds of ohms.

MAP voltage can be measured by back probing the pigtail terminals with engine running.

cruiser54 said:

IAC will not cause rich running. It only affects idle speed.
TPS will not cause a rich condition either.
An overly rich mixture is caused by MAP, CTS, and IAT. In that order. My money is on the fact that the hose from the throttle body to the MAP sensor is cracked, melted, or somehow or another messed up as a result of being disturbed in the repair process.

Click to expand...

You left out the FPR, Fuel Pressure Regulator, leaking gas into the vacuum line which really sucks, LOL!:wave:

His description sounds like the vac line to the MAP sensor is loose at the throttle body,

or a bad FPR (see if there is any gasoline odor in the vacuum line to the FPR, it is on the front of the fuel rail on the fuel injectors.

A leaking injector, stuck open is also possible, but not as common.

A bad O2 sensor, or heater relay or wires to the O2 sensor damaged is also possible. May be all three!

Ecomike said:

You left out the FPR, Fuel Pressure Regulator, leaking gas into the vacuum line which really sucks, LOL!:wave:

Click to expand...

True.

I know you probably have but did you make sure you didnt crack or have cracks in the intake / exhaust manifold when you pulled it off?