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" Q: I have a 1991 Jeep Cherokee with 228,000 miles. It is equipped with a 4.0 liter straight Six. It ran hot so I pulled over to cool it down and filled the coolant. Now when it&amp;#039;s standing still, it will run hot. I put in a new radiator, thermostat and electric fan (Now it has has two). It will get about 240 degrees at standing still, but not into the red zone. There is no oil in the water; it has not lost any power; it doesn&amp;#039;t leak oil or water; and I&amp;#039;ve never had to add oil between oil changes. What&amp;#039;s causing this problem?  A: Replace the water pump. Sounds like the pump impeller is corroded away. Q: I&amp;#039;m puzzled about the logic that Fuel Injectors are &amp;quot;shut off&amp;quot; when I take my foot off the gas pedal. If that&amp;#039;s the case, then what keeps the engine running? We were told that there is no rear pumping action in the transmission to turn the engine with the drive wheels. So, when I take my foot off the accelerator, the injectors receive no electrical signals to open, and no fuel is injected into the cylinders. Yet my tachometer is not at zero. What&amp;#039;s causing the engine to turn? Of course momentum for a few seconds. But after that? Keep up the outstanding work you guys do. Popular Mechanics is absolutely the greatest! Don&amp;#039;t ever change. A: &amp;quot;We&amp;#039;re told there is no rear pumping action in the transmission to turn the engine with the drive wheels.&amp;quot; Wrong. Wrong, wrong wrong. Whoever told you this is incorrect. Regardless of whether the transmission is manual or automatic, the engine continues to rotate because the rear wheels are turning at road speed. Power comes from the rear wheels back to the engine through the transmission. As the car slows down, so does the engine. When the engine slows back to idle speed, the injectors are turned back on. Q: I have a 1999 Ford F150 pickup truck 5.4 with 113,000 miles. I had a few missfires last year, so I finally decided to replace all the COPs and now it runs great. Now I have a P133 (O2 sensor slow circuit response sensor 1 bank 1) showing up in the scan tool. I have an Acctron diagnostic hooked up and see the O2 sensor voltage changing constantly between .2v to .7v. Is the sensor gone? Almost everything I read says the almost never go bad.  A: 113K is well past the design life of an O2 sensor. As these sensors age, their ability to swing their voltage diminishes. Yours has apparently slowed down. Replace it.  Q: How do I check tire inflation? Where are the sensors located and how do they work? Mine seem to be malfunctioning. Every time I start the car the computer tells me to check my tires, but the tire pressure is not low. A: Some cars use discrete, battery-powered sensors inside the wheel. Others use data from the antilock braking system to compare the rolling radius of the tires to each other, without an actual pressure sender. A tire with lower pressure than the others will rotate at a different angular velocity. You&amp;#039;ve neglected to tell me what kind of car you have. If you have wheel senders, they may need to be resynced to the tire-pressure monitor system. If your vehicle uses ABS sensors, you may have a worn or mismatched tire that&amp;#039;s not the same diameter as the others. Q: I have a 1998 Ford Windstar 3.8L Engine with 208,000 miles. It tends to hesitate when I&amp;#039;m stopped at a light while the transmission is engaged, or it feels like it&amp;#039;s choking and wants to stall about every 30 seconds when it&amp;#039;s parked with the transmission engaged. When this happens, I watch my tachometer drop momentarily from normal (approximately 700 rpms) to 500-450 rpms and then back up to normal, 30 seconds later it does it again, and then again. No problems when the vehicle is in motion or when the vehicle transmission is in park or neutral. This problem started at around 170,000 miles. This problem does not cause the check engine light to come on. Can you please assist me in possibly identifying the problem? I&amp;#039;d like to keep the vehicle for another 100,000 miles. A: Dollars to donuts there&amp;#039;s a leak between the manifold airflow sensor and the throttle blades. These aren&amp;#039;t vacuum leaks, but they will cause surging and poor idle. The MAF sensor isn&amp;#039;t seeing all the air that&amp;#039;s going to the throttle, and makes the engine run lean. "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/cars/how-to/a2557/4247550/>