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Rough Idle and I am stumped??

3K views 7 replies 6 participants last post by  360ci 
#1 ·
I am have very rough idle issues on my 02 Taurus 3.0 U motor. Car bounces at very low RPM until it dies, but seems to run fine while driving. I had codes pulled at AutoZone and it showed lean on bank 1 and 2. Misfire on 2, O2 sensors and MAFS. I have since replaces plugs, wires, MAFS, coil and had recently replaced the fuel filter and IAC. Im not sure what else could possible cause this problem. Would a bad O2 cause the car to idle horrible but run fine? It is dumping fuel into the oil like no tomorrow and I have noticed a milky substance inside the the tube connecting the air filter to the throttle body. I would appreciate any assistance.
 
#2 ·
For all the money you've spent on parts so far, you could have bought a decent scan tool. What you really need to see at this point is live data from the computer telling you what the "fuel trim" is at and what the oxygen sensors are reading. When the computer sees a lean condition, it adds fuel. But the computer max's out at 25% additional fuel. If your fuel trim is at 25%, that's a dead giveaway for a vacuum leak. A vacuum leak would show up more at idle than at higher RPMs. A vac leak can be anything from a broken vac hose to a stuck open EGR valve, to a bad intake or head gasket.

Read the post below on engine misfires to get the whole picture.

Engine misfire codes
 
#3 ·
Wouldn't I notice antifreeze in the oil if the head gasket was blown? I had a vehicle in the past that had that problem and the oil had that "milky" color to it. I checked all the vac hoses and they all appear to be in good condition. I had the vehicle scanned at AutoZone and was given codes for lean on both banks, O2 sensors, MAFS and misfire on cylinder 2. I guess I should take it to a shop for a decent diag scan? Thanks for the input!! I will step back and punt!!
 
#5 ·
Dumping gas into the oil could be a ruptured fuel pressure regulator. Most likely.
Milky white substance in the air tube is condensation. Engine not getting hot enough or
car run on very short trips not getting the engine up to temp. or lack of proper oil changes soon enough. The later is usually the problem. Excess gas getting into the oil is called a wash down. In laymans terms also called " going to need a new engine soon "
if not fixed NOW. Yes a head gasket can blow and not get water in the oil. Common. You
don't have that problem. Without know the history of your car it seems to me your engine has been short of maintanance. Neglected. You should NOT find moisture in the air tube.
Just my opinion.
 
#8 ·
Cheap fix...at a dealer??? NO SUCH THING. Well, only if they don't charge labour out of respite for what you told them you spend already trying to fix it....

thanks for the update!!
 
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