Rick's Free Auto Repair Advice

Posts Tagged: rough idle

P0172 trouble code and fuel in oil plus rough idle and engine run-on

GM has a fix for a P0172 trouble code and fuel in oil, rough idle, and engine run-on GM has issued a service bulletin #PIP4783B to address a P0172 trouble code and fuel in oil, rough idle, and engine run-on the GM vehicles listed below. Before you perform any diagnostic tests, pull the engine oil dipstick, and check for the presence of fuel. GM has determined that a P0172 System Too Rich (Bank 1) may be caused by a defective high-pressure fuel pump that’s leaking fuel into the crankcase when … Read More

P0505, P0506, hard start, rough idle

Fix P0505, P0506, hard start, rough idle on Ford vehicles Fix P0505, P0506, hard start, rough idle Ford has issued a service #12-7-4 to address trouble codes P0505, P0506, hard start, rough idle on the vehicles listed below. The vehicles may also store enhanced trouble codes P2111 and P2112 after the keep alive memory has been cleared, the battery has been disconnected or the vehicle has a dead battery. On vehicles with over 10,000 miles the problems may be caused by sludge buildup in the electronic throttle body. That causes … Read More

Rough idle – Ford

Why do I have a Rough idle – Ford Ford has issued a service bulletin to address a rough idle problem on 2009 Ford Escape and Mercury Mariner vehicles with the 2.5L engine and six-speed automatic transmission built before 3/5/09. The rough idle appears when first started after an extended soak. The bulletin says that the rough idle usually happens with the transmission in Drive and the engine loaded (like when AC is on). As is more common these days, the problem is due to faulty software. Before you spend … Read More

How does an idle air control valve work

What is an idle air control valve Many people are confused about how idle air control valves work. An idle air control valve literally bypasses air around a closed throttle plate so the engine can get air at idle. Because it bypasses air, it’s also called an air bypass valve. Back in the days of carburetors, idle speed was adjusted by way of an idle speed screw. In fact, on many carburetors there were two idle speed adjustment screws; one for hot idle and another for cold. Turning the screw … Read More

Transmission slips – GMC Safari

Transmission slips – GMC Safari Rough engine and slipping transmission on 2004 GMC Safari van with the 4.3L V-6 engine. Before you even think of adding anything to your engine or transmission, clean your mass airflow sensor (MAF) sensor. It’s one of the known causes of engine and transmission issues. The MAF sensor is located in the air duct between the air filter box and the throttle body. The sensor contains heated wire elements that are cooled by the inrush of fresh air. The sensor measures how much power is … Read More

Rough idle Mazda 3

Rough idle Mazda 3 Rough idle, bad gas mileage on Mazda 3 with the 2.0-litre engine A vacuum leak can cause both a rough idle and poor gas mileage. And on this vehicle the positive crankcase ventilation (PCV) valve hose can leak and be very hard to diagnose. Even professional shops with smoke machines have a hard time finding this one. The hose is located under the intake manifold. Since new hose is cheap, try replacing it and the PCV valve and see if the condition improves. I’m betting it … Read More

Rough idle, high idle

Rough idle, high idle Both a rough idle, high idle can be caused by a vacuum leak or carbon buildup in the throttle body. Diagnose and fix a car has rough idle condition Any time you see a rough idle  or hunting idle (idle speeds up and slows down), suspect a vacuum leak. Extra air leans out the exhaust mixture, which is detected by the oxygen sensor and reported to the powertrain control module (PCM). To correct the lean condition, the PCM adds fuel. As the engine speeds up, the … Read More

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