Have a 2006 TB with the 4.2L engine. It has 120,000 miles, and has started to run rough at idle after a few minutes. The symptoms are:
1. Somewhat rough idle after thorough warm-up. Idle is at about 650 rpm.
2. When cold, and idling at about 650 rpm in gear, it runs smooth.
3. There is no misfiring at idle or when driven on the road.
4. There are no stalling problems.
5. It has good power.
6. After extended highway speed driving for several hours, I noticed when I stopped and allowed the engine to idle that it took several minutes before the rough idle would begin. Idle would be at about 650 rpm.
The engine maintenance history is:
1. Oil changes every 3k~4K since new with 5W-30 Valvoline natural oil and AC filter.
2. Spark plugs changed at 60,000 and 119,000 using AC spark plugs as listed in the owners manual.
3. Throttle body was removed and cleaned with CRC throttle body cleaner at 30,000, 60,000, 90,000, and 120,000.
4. The intake manifold was removed at 106,000 and the manifold gaskets, the valve cover gasket, and the fuel injectors were replaced. By the way, the manifold bolts were loose from the factory and I torque tightened them per the specification listed in the Haynes manual.
5. The spark plug coil tubes were replaced at 106,000.
6. The variable valve timing solenoid was replaced at 99,500 as a precaution against the oil screens over the ports loosening at traveling through the oil circuit. All screens were intact on the old VVTS.
7. Thermostat was replaced at 106,000.
8. Alternator was replaced at 102,000.
9. MAF sensor has been removed and cleaned over the years at regular intervals with the last cleaning occurring last summer.
10. Installed new rubber plug on intake manifold port to replace age-cracked plug.
11. Inspected the brake booster valve and brake vacuum hose and both appear to be good and functional.
Any hints as to what might be causing the rough idle? I have not checked fuel pressure or the exhaust air injection system. I'm not sure if the air injection system would contribute to this problem. Also, I don't see an underhood sticker for vacuum hose routings, or I would have checked them too.
1. Somewhat rough idle after thorough warm-up. Idle is at about 650 rpm.
2. When cold, and idling at about 650 rpm in gear, it runs smooth.
3. There is no misfiring at idle or when driven on the road.
4. There are no stalling problems.
5. It has good power.
6. After extended highway speed driving for several hours, I noticed when I stopped and allowed the engine to idle that it took several minutes before the rough idle would begin. Idle would be at about 650 rpm.
The engine maintenance history is:
1. Oil changes every 3k~4K since new with 5W-30 Valvoline natural oil and AC filter.
2. Spark plugs changed at 60,000 and 119,000 using AC spark plugs as listed in the owners manual.
3. Throttle body was removed and cleaned with CRC throttle body cleaner at 30,000, 60,000, 90,000, and 120,000.
4. The intake manifold was removed at 106,000 and the manifold gaskets, the valve cover gasket, and the fuel injectors were replaced. By the way, the manifold bolts were loose from the factory and I torque tightened them per the specification listed in the Haynes manual.
5. The spark plug coil tubes were replaced at 106,000.
6. The variable valve timing solenoid was replaced at 99,500 as a precaution against the oil screens over the ports loosening at traveling through the oil circuit. All screens were intact on the old VVTS.
7. Thermostat was replaced at 106,000.
8. Alternator was replaced at 102,000.
9. MAF sensor has been removed and cleaned over the years at regular intervals with the last cleaning occurring last summer.
10. Installed new rubber plug on intake manifold port to replace age-cracked plug.
11. Inspected the brake booster valve and brake vacuum hose and both appear to be good and functional.
Any hints as to what might be causing the rough idle? I have not checked fuel pressure or the exhaust air injection system. I'm not sure if the air injection system would contribute to this problem. Also, I don't see an underhood sticker for vacuum hose routings, or I would have checked them too.
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