I have a 2002 Dodge Durango with a V8 Magnum engine with 89,000 miles that has an engine surging problem. The engine tachometer surges at idle from approximately 500 RPM’s to about 1800 RPM’s usually in the morning but at other times also. Recently, when driving with the cruise control on, the engine will start surging and the cruise control will shut off and the car starts bucking. A few weeks ago the car started stalling and eventually would not start. The dealerships have cleaned the throttle body a couple of times, replaced a vacuum hose and also cleaned something else related to the throttle body that they said had carbon deposits. Each time the car runs fine for a few days and then develops the same symptoms again. We have had it to 2 separate dealerships a total of 5 times in the last 4 weeks. Any suggestions?
In the throttle body are the Idle Air Control valve, and the throttle valve. The PCV (Positive Crankshaft Ventilation) valve releases into the air intake tube, which leads into the throttle body. How CAN the throttle body get dirty since there is an air filter to filter incoming air? The PVC is laden with carbon dust and oil as it does come from the crankcase which gets there as blow-by from the cylinders. Poorly sealing piston rings (worn) will allow excess blow-by, which goes into the throttle body, which fouls the IAC and throttle plate. The condition of the piston rings can be gauged by vacuum and cylinder compression tests. If those tests show a problem, a knowledgeable mechanic can tell you the NEXT step.