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" Senior Editor Mike Allen answers readers&amp;#039; car questions. Q: I have a 1991 full size 4-wheel 5.7 GMC Jimmy with 131,472 miles on it that has everyone stumped. When I first start it up in the morning it runs rough and wants to stall. After a short time it clears up. When I stop for a light it idles rough and wants to stall. Other than that it runs well. I replaced the I.A.C.-T.P.S.- E.G.R. sensors and had a complete tune up with a new distributor and a new throttle body gasket installed. The injectors were cleaned out by the the repair shop and it still did not correct the problem. Any help will be appreciated. JOE SROCZYL A: .I&amp;#039;d start chasing an air leak, either a vacuum leak or a metered-air leak (between the MAF sensor and the throttle body. Q: I&amp;#039;m shopping for a used car. I want one with ABS--is anti-lock brakes the same as ABS? How can I tell if a particular car is so equipped? Is it possible to lift the hood and find the special valving used for ABS in plain sight? FRANK A: ABS is the acronym for Antilock Braking System. Most cars have the ABS controller mounted underhood, although a very few park it elsewhere. Q: I have about 100,000 miles on my 1996 Ford Crown Victoria. I drive about 25 miles per day at 55 to 65 miles per hour. If we take a trip somewhere, and travel the interstate, we travel at about 75 miles per hour. Very normal driving habits. The oil is changed every 3000 to 4000 miles. The only repair under the hood was to replace the intake manifold after a hose under the intake began to leak, and the manifold was warped and had to be replaced with an aftermarket part. My husband is retired from owning and operating an automotive machine shop, so he does most of the repairs on our vehicles. He thinks that the spark knock problem may be because of carbon build up in the heads. Before we go into the engine, I want to know if there is a way to eliminate this spark knocking without having to do this. This is the best, most trouble free car I have owned. The only thing is the spark knocking. When accelerating, at about the speed when the automatic transmission shifts, there is the spark knocking. I back off the speed a little, and the noise lessens, and as highway speed is finally achieved, it is almost gone, but returns just as bad when I accelerate up the next hill. LAVERNE MIXON A: I&amp;#039;d take really close look at the EGR (Exhaust Gas Recirculation) system before I pulled the heads. Even if the EGR valve is operating properly, the passages in the manifold may be plugged or restricted. Q: I have a 2001 Chevy 2500 HD Silverado with the 6.0 L engine. It has a problem with a super fast idle after being driven for 20 to 30 minutes at highway speed. When the clutch is pushed in and the transmission taken out of gear, the engine wants to run about 3,000 RPM until it is shut off. After being shut off for a few minutes the engine slows back down to the proper idle speed. This never happens in stop and go driving. The GM garage told me it was because of a faulty EGR valve that was making the Check engine light come on. I replaced the EGR and is still does it. What is wrong? A: I&amp;#039;m not buying the EGR being the issue. I&amp;#039;d look either for an intermittent partially stuck throttle, a bad throttle position sensor, or a bad idle air controller. What code was it setting before they replaced the EGR (the mechanic should have written it down on the repair order), and what code is it setting now? Q: I have a well maintained 1999 Buick Regal 3.8 LSE with 81,000 miles. The car runs great in the city with good gas mileage. The problem is when I&amp;#039;m driving on the highway. After travel for about 20 to 30 miles, the car starts to hesitate(a/c on or off). I can feel the jerking and the tachometer goes up and down. After a few more miles the hesitating stops. Sometimes it starts again other times it doesn&amp;#039;t. This has never happened when driving under 60 mph. WILL BENNETT A: Get a scan tool in flight recorder mode to capture data while it&amp;#039;s hesitating. Q: I have a 1996 Astro Van. The a/c heater fan will no longer go on High. The first 3 positions work. I have been told it is a burned out relay, a fuse (which I cannot find) a resistor, or the switch. What do you think? CAREY A: Go to PM&amp;#039;s November 2005 Auto Clinic.  "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/cars/how-to/a754/3468061/>