I have a 2000 1.6-liter Honda Civic with 110,000 miles. Recently a valve lifter began to clatter on start-up. It's quiet for 15-30 seconds then clatters for up to a minute before quieting down. After warm-up the engine runs quietly. I had the valves adjusted per the manual but it didn't get better. My mechanic thinks oil gets wiped off the lifter in the first few seconds so the clattering begins. Then as the oil warms and flows to the lifter, it quiets down. Do you have any thoughts or suggestions?
There is some logic to your mechanic's thinking, particularly in light of Honda's recommended oil/filter change interval in "severe service" conditions — every 3,750 miles! Some type of varnish or sludge buildup may be restricting oil flow to the valve train.
But here's my thinking. The lack of oil on the cam lobe/lifter face wouldn't change the clearance between valve and lifter — thus is not likely to be the source of the clatter. Valve clatter is generated by excess clearance between the valve and lifter.
A sticking valve may be causing the temporary clatter. On cold start-up, residual oil on the valve stem is drawn down the valve guide and burned. Wear and carbon buildup on the valve stem and valve guide may be sticking the valve until enough oil flow and heat reaches these parts to allow full valve movement. Adding half a can of SeaFoam Motor Treatment to the oil can help remove varnish and sludge, and I've actually removed valve covers to pour SeaFoam directly down the valve stems on a warm engine to expedite the cleaning process.
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I have a 1998 Ford Expedition with a 4.6-liter engine and 241,000 miles. This winter I've started having a throttle icing issue. After driving for 15-20 minutes on the freeway, the throttle butterfly freezes and sticks at 1,500 to 2,000 rpm. I pulled the air intake off and found an ice buildup in front of the butterfly on the bottom of the throttle body. I also get a moisture buildup inside the oil filler cap. I pulled the positive crankcase ventilation (PCV) valve after the car had sat overnight — it was iced up.
I replaced the PCV and put some cardboard in the grille to see if I could keep the engine a little warmer. After 150 miles the problem hasn't happened again yet. I think the moisture is coming up the small tube connecting the driver's side of the engine block up to the front of the throttle body because that tube was full of the white gunk. I've found Ford technical service bulletin 01-21-5 that describes a "PCV service kit" for this problem. Can you tell me what the service kit is and if it's worth giving it a shot?
The kit upgrades the PCV valve to a heated PCV valve. The new valve has connections for coolant flow from the original engine coolant temperature sensor to the new valve, then a new hose is installed to carry the coolant from the new PCV valve back to the ECT sensor. By keeping the PCV valve hot, moisture won't condense, freeze and block PCV flow or ice the throttle plate.
From the work you've done, I'm sure you can install this upgraded PCV system yourself. I found the kit available online for less than $50.
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I have a 2002 Chevy 1500 with the small V8 engine. It no longer gets the 20-plus miles per gallon it used to. The truck has about 125,000 miles on it. Any recommendations to restore the mileage?
Have your shop check the front oxygen sensors' "cross count" rate. These measure how fast the sensors react to changes in the percentage of oxygen in the exhaust. As these sensors age, they slow down. A lower cross count rate prevents the electronic control module from fine-tuning the air-fuel ratio as efficiently, and mileage suffers. At 125,000 miles, it may be time for fresh oxygen sensors.
Paul Brand, author of "How to Repair Your Car," is an automotive troubleshooter, driving instructor and former race-car driver. Readers may write to him at: Star Tribune, 425 Portland Ave. S., Minneapolis, Minn., 55488 or via email at paulbrandstartribune.com. Please explain the problem in detail and include a daytime phone number.
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