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Wanted to update this thread about my engine problem.
Bought a scanner and recorded live data. Noticed abnormal upstream and downstream O2 sensor voltages and fuel trims. Diagnosis: Faulty O2 sensors. They both had over 100,000 miles on them, so I replaced both (Denso, $28 each at RockAuto.com), and the engine runs nice and smooth again, and fuel mileage is much better.
Don’t forget to chase the manifold threads, and coat the sensor threads with anti-seize lubricant.
Lesson learned: Get a scanner and learn to use it to diagnose problems. The Scannerdanner.com forum was a GREAT help in the diagnosis. Those guys are really helpful and dedicated.
Next: CV axles, oil seals, front brake pads, and rotors!
I hate my life.
MDK22:
– Intake has never been smoke tested.
– I’ll check the cam & crank sensorsI did check the Throttle Position Sensor tonight, and all the voltage and resistance values were good when closed and wide open.
Again, this bogging down problem occurs once the engine warms up, cruising at 65-70 MPH. When I slowly press on the gas, there’s no response for about 1/4″, and then the engine kicks back in, and runs OK, but I’m quickly up to 80 MPH, and I don’t know if it will continue to run OK at that speed, because I slow down – who needs a speeding ticket?
Thank you for your continued help.
MDK22:
– Intake has never been smoke tested.
– I’ll check the cam & crank sensorsI did check the Throttle Position Sensor tonight, and all the voltage and resistance values were good when closed and wide open.
Again, this bogging down problem occurs once the engine warms up, cruising at 65-70 MPH. When I slowly press on the gas, there’s no response for about 1/4″, and then the engine kicks back in, and runs OK, but I’m quickly up to 80 MPH, and I don’t know if it will continue to run OK at that speed, because I slow down – who needs a speeding ticket?
Thank you for your continued help.
UPDATE (response to new comments):
1. The smell comes into the cabin with the windows down, and resembles if you took a sniff of the inside of the valve cover through the oil fill cap – part oil, part fuel, part exhaust. And I only smell it when the problem starts.
2. I’ve been super diligent with oil and filter changes, and just changed them (Castrol GTX 10w-30, Fram)
3. Coolant was changed in July 2011 with new radiator hoses.
4. Radiator fan does kick on and cycles on/off.
5. No squealing belts.
6. No check engine light
7. No diagnostic trouble codes reported to the scanner
Guy at O’Reilly’s mentioned that it might be the Throttle Position Sensor. What do you guys think about that?
Also, as for the extremely rough running, stalling when I left off the gas, and not starting until it cooled down, this was fixed with a new cap & rotor (rotor screw had come out and rotor was flopping around inside).
So, I’m back to the original problem I’ve had for the past 4 years: When cold, it starts right up, idles smooth, and runs great. But, on the highway at 65-70 MPH, as soon as it warms up it starts bogging down and running rough. And if I don’t move the gas pedal, it slows down to 40-45 MPH, and then kicks back in. If I slowly press on the gas pedal, there’s no response for about 1/4″, then it kicks back in, but then I’m going too fast, so I let off the gas to slow down to 65-70 MPH, and the problem repeats.
UPDATE (response to new comments):
1. The smell comes into the cabin with the windows down, and resembles if you took a sniff of the inside of the valve cover through the oil fill cap – part oil, part fuel, part exhaust. And I only smell it when the problem starts.
2. I’ve been super diligent with oil and filter changes, and just changed them (Castrol GTX 10w-30, Fram)
3. Coolant was changed in July 2011 with new radiator hoses.
4. Radiator fan does kick on and cycles on/off.
5. No squealing belts.
6. No check engine light
7. No diagnostic trouble codes reported to the scanner
Guy at O’Reilly’s mentioned that it might be the Throttle Position Sensor. What do you guys think about that?
Also, as for the extremely rough running, stalling when I left off the gas, and not starting until it cooled down, this was fixed with a new cap & rotor (rotor screw had come out and rotor was flopping around inside).
So, I’m back to the original problem I’ve had for the past 4 years: When cold, it starts right up, idles smooth, and runs great. But, on the highway at 65-70 MPH, as soon as it warms up it starts bogging down and running rough. And if I don’t move the gas pedal, it slows down to 40-45 MPH, and then kicks back in. If I slowly press on the gas pedal, there’s no response for about 1/4″, then it kicks back in, but then I’m going too fast, so I let off the gas to slow down to 65-70 MPH, and the problem repeats.
UPDATE:
First off, mucho thanks to all you guys for offering help. I really appreciate it. You are good and decent men. It restores my faith in mankind.
Forgot to mention that the Check Engine light is NOT on, and there are no trouble codes reported when connected to a scanner.
What I’ve done so far:
Replaced fuel filter
Changed oil & filter
Adjusted valve clearances
Checked timing
Checked PCV valve
Checked fuel pump/pressure
Replaced cap & rotor (rotor screw had come out, rotor was flopping around, loose screw was arcing)
Replaced spark plugs
Replaced Coolant Temperature Sensor
Replaced Coolant Temperature Switch
Cussed multiple timesProblem persists.
But, when the engine is cold, it starts right up, idles smooth, and runs real nice.
F me.
UPDATE:
First off, mucho thanks to all you guys for offering help. I really appreciate it. You are good and decent men. It restores my faith in mankind.
Forgot to mention that the Check Engine light is NOT on, and there are no trouble codes reported when connected to a scanner.
What I’ve done so far:
Replaced fuel filter
Changed oil & filter
Adjusted valve clearances
Checked timing
Checked PCV valve
Checked fuel pump/pressure
Replaced cap & rotor (rotor screw had come out, rotor was flopping around, loose screw was arcing)
Replaced spark plugs
Replaced Coolant Temperature Sensor
Replaced Coolant Temperature Switch
Cussed multiple timesProblem persists.
But, when the engine is cold, it starts right up, idles smooth, and runs real nice.
F me.
UPDATE:
Cold engine starts right up and idles smoothly. I let it idle until it warms up to operating temperature. Still runs fine. I turn the engine off, try to restart it…it won’t start. It just turns and turns and turns.
Removed and cleaned the Idle Air Control Valve – a real pain in the ass. Waste of time. Nothing improved.
Also, a friend pulled the dip stick and said it smelled like the oil had gas in it. What the hell?!
HEEEEEEEEEEEEEEEEEELP!
UPDATE:
Cold engine starts right up and idles smoothly. I let it idle until it warms up to operating temperature. Still runs fine. I turn the engine off, try to restart it…it won’t start. It just turns and turns and turns.
Removed and cleaned the Idle Air Control Valve – a real pain in the ass. Waste of time. Nothing improved.
Also, a friend pulled the dip stick and said it smelled like the oil had gas in it. What the hell?!
HEEEEEEEEEEEEEEEEEELP!