I have a 97 kia sportage. I think i have a exhaust leak. can that have the check engine light on? AND is that the manifold that need to be fixed?

It is important too identify the following:
1) The source of the exhaust leak
2) The source of the oil leak.
The exhaust leak could turn out to be a bad exhaust gasket, a cracked or loose exhaust manifold, a cracked cylinder head or bad gasket, or related parts. The oil leak could turn out to be the valve cover gasket. A dried out valve cover gasket can cause oil to sit on the spark plugs and have oil leaks. Be sure not to over-fill the oil. A machine shop can find cracks in cylinder heads. If these problems turn out to be ok (and one of those stethoscopes may be helpful) then you could procede to check fuel delivery. (there will be pressure in the lines) A lot of times connectors get corroded. I noticed on this model the sensor for the engine cooling mounted near the thermostat is very sensitive to variation. Same for the air sensors if left loose.

O2 or HO2S
that is the question
O2 sensors are after the cat converter/s where as HO2S sensors are in the exhaust manifold before the cat converter/s and report exhaust gas composition to the ECM so that the air /fuel mixture can be adjusted
May be you replace the wrong sensors

flywheel'flexplate 73 ft lbs Exhaust nuts 31 foot lbs Exhaust bolts 18 ft lbs
You say pressure plate, is this manual transmission?

Spray around the intake manifold with carb cleaner. If the engine smooths out or revs up, fix the leak. It sounds like a leaking intake manifold gasket.

Please don't forget to rate! Thanks a bunch!

Trouble Code P0171---Fuel System Too Lean (Bank 1)

Trouble Code Conditions:
Engine running in closed loop at a speed of over 5 mph for 2-3 minutes, and the PCM detected the Lambda correction value exceeded the "high" Threshold limit, condition met for 200 seconds.

Possible Causes:

• Air leaks in intake manifold, exhaust pipes or exhaust manifold
  
• One or more injectors restricted or pressure regulator has failed
  
• Air is being drawn in from leaks in gaskets or other seals
  
• O2S element is deteriorated or has failed
  
• A "fuel control" sensor is out of calibration (ECT, IAT or MAP)
  

The O2 sensors on these are a common issue as well as the "pre cat" bolted onto the exhaust manifold. Remove the coil packs and plug wires and look for white tracking indicating an electrical leak. This is also common on these models. Look for oil leaking into the holes of the spark plugs. If you have a severe lack of power and low exhaust flow, it is probably the "pre catalytic converter". If everything else checks out, I would disconnect the exhaust at the cylinder head and pull it back about 1/2"(inch) and see how it runs. Let me know and I will walk you through the rest.

code po170 fuel system too rich or too lean bank 1. this is 5 possible causes 1. air leaks present in the exhaust manifold or exhaust pipes.2.air being drawn in from leaks in engine gaskets or other seals. 3.incorrect fuel pressure or one or more fuel injectors has failed. 4.front ho2s element is contaminated or has failed. 5.a fuel control sensor is out of calibration- baro sensor - ect sensor - iat sensor.

Fix the leak at the emissions system first. There is a small leak that the PCU detected. That could be the cause of the P0116 problem. Also the PCU detected a lean gas mixture because it is getting more air to the fuel system than gasoline. Start with the leak , then the Engine temperature sensor. I think that fixing the lek will "fix' the othe 2 problems. but it could be either one or all of them.

you'd have to remove the engine its on the back.

Ok I think you meant code P0171, this means the fuel trim is always lean, you need to check for a engine vacum leak, maybe a cut or damaged PCV hose or any other hose that is in the vaccum system, I have read other Kia owners (Kia Forums, you should join one) reports of this same code, most found it not to be the O2 sensor but a vacuum leak.