4.0 Running Rich

Ok, thanks for the information. Do you think the plugs have anything to do with it being rich because I definitely need to change them and what do you think about the antifreeze loss?


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Plugs don't cause a rich fuel mixture problem. Can't say what's causing the coolant loss. Leaking water pump, blown head gasket, radiator, hoses, you're gonna have to look around. If there are no obvious leaks ya gotta lean towards a blown head gasket.
 
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Jerry Bransford said:
Plugs don't cause a rich fuel mixture problem. Can't say what's causing the coolant loss. Leaking water pump, blown head gasket, radiator, hoses, you're gonna have to look around If there are no obvious leaks ya gotta lean towards a blown head gasket.
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I was leaning toward a blown head gasket, but the oil isn’t milky, there is no white smoke, and the exhaust smells like exhaust. I smell antifreeze along the radiator seam by the rad cap, so I’m thinking a bad radiator or the radiator cap is allowing the coolant to evaporate. I was thinking maybe a plug wasn’t firing, but that wouldn’t cause the abnormal fuel consumption. I don’t see any hoses leaking either and the water pump looked dry. I’m at a loss with these two things. Most likely time to take it to a mechanic.


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I'd probably change the IAT sensor first. When you unscrew it it may even just be covered in soot. If it is cleaning the soot off may help.
 
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So I pulled the IAT and it was a little sooty, so I cleaned it off and it looked like it was in good shape. The Jeep is still getting 9 mpg and smells rich. I replaced the plugs and they were definitely due. When I walk behind the Jeep when it is off, it smells like gas bad around the tank. Idk what to due. The temperature readings are right too.


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I drove all town miles this past week and only went 30.8 miles. I drive very easy and don’t let it rev above 3000 rpms, but I don’t lug it either. I got 7mpg. I looked at a gas mileage thread and people get over 200 miles per tank and I can’t even get 150 per tank. One week I was on the highway a lot and I got 9.9 mpg. Something is seriously wrong. Any other suggestions?



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Bumping this up to see if OP ever found his issue. Im having similar fuel issues. Smells rich, getting 10 mpg. New NTK O2 sensors. new plugs, new coil, new cap and rotor, new injectors. Ran great for about 2 weeks after changing all that and now its back to running rich with a strong exhaust smell. Engine temp is right at 210. Getting my scan tool back this week to check my IAT readings. No CEL but could possibly have some DTCs. Wont know till I get my scanner back from my friend on Thursday. Could a bad cat cause this issue?
 
Not to throw this off course, but I had a similar problem on a 96 Nissan. I must have been getting like half the milage I was expecting when I got it. It turned out to have a tiny leak just above the fuel pump. Right where all the dirt and mud collect. When you step on the gas it would let some fuel pass out into the dirt above the tank. But if it was just idling it wouldn't. So every time I'd be searching for any fuel problems it would just put like a kitten.
This may be non-aplicable to this thread, but throwing it out there in case it helps someone.
 
Brian83 said:
My issue was a failed cat.
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I'm going to try a few things. O2 sensor, try to get a new canister and Mopar sensor, check O2 sensors, maybe replace cat and then injectors if that doesn't work. man, i hate to spend that money. haha

I don't believe the canister would cause it to run this rich.
 
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