Vehicle: !998 Ford F150 4.6L. p0171. p0174. commented Aug 27, 2017 by inspector (101 points) yes by not properly controlling egr due to and or venting vacuum ; all of this while engine running. can also cause ac to deflect to defrost vents in some older explorers / mountaineers. If this cooler fails or the coolant passages become clogged (a common occurrence on the 6.0L), it may reduce flow to the EGR cooler, or create a sludgy oil/coolant mix that won’t flow through the cooler. If your engine has fuel issues, it can increase the amount of soot in the exhaust which will then coat and often plug your EGR cooler zombie1969. Check if the PCV valve is working properly.A plugged PCV or collapsing vacuum hose will cause excessive crank case pressures and blow oil from every seal or gasket. "Suddenly is has some serious blowby and at both the oil filler tube at the front of the intake manifold and from the road draft tube at the rear of the block. ". Problems That May Cause a Lean Condition. A bad oxygen sensor; Vacuum leak (possible symptoms: rough idle, stalling or fast idle) Bad engine coolant temperature sensor; EGR valve leaking into the intake manifold; Faulty mass airflow (MAF) sensor; Faulty fuel pressure regulator; Dirty or clogged fuel filter; Dirty or clogged fuel injector If you would like to boost your automotive knowledge, keep reading. This article outlines three common causes of EGR valve problems. 1. Faulty Temperature Sensor. As discussed above, the most important goal of the exhaust gas recirculation system involves reducing nitrogen oxide levels. Check the engine light. When the fuel to air ratio is high, you will have the check engine light coming on. The engine control module controls all the sensors, and if a sensor in your car misfunctions, it will light up the check engine light on your dashboard. 2. Fuel smell from exhaust. Exhaust Gas Recirculation (EGR) Valve. First, The Exhaust Gas Recirculation (EGR) Valve, is a mechanical device. And, just like valves and the throttle body, it can develop carbon buildup. And, most often that prevents it from, closing fully. When that happens, the (EGR) valve, allows exhaust flow at idle, which causes a rough engine idle Some of the likely causes include, Faulty injectors – stuck open. Worn piston rings or cylinder glazing. If equipped with glow plugs, could be faulty plugs or module. Remember, if you have an older engine with really low compression and bad timing or low injection pressure, you are more likely to have white smoke. I had the same issue with my 04 civic. it's a common issue. it's actually the plastic plug on the side of the valve cover. you have to take the EGR valve off to get to it. so you need to order the plastic plug and an new egr gasket. the hardest part was getting the egr valve off as it's a bit of an awkward angle. Clogged PCV Valve. When a PCV valve stops working, pressure builds up inside the valve cover. This pressure can cause a number of problems for the engine, including an oil leak, particularly at the valve pan gasket. Clogged PCV valves may make an engine run poorly, decrease gas mileage and increase vehicle emissions. BGZflDK.