Expert Advice: September/ October 2008 Edition

Ford Battery Woes
Q: I just changed out the electronic control module, distributor cap, coolant fan, and battery, and installed a new alternator (second one in three days) on my 1993 2WD Ford F-150 with the six-cylinder engine. When testing the battery and the alternator, the alternator isn't getting excited enough and my battery keeps draining. I've soldered and shrink-wrapped the leads from the alternator, and the battery light indicator on the dash display is still on.   |   expert Truck And Suv Advice ford Battery Woes A: Ford ran into trouble with multiple alternator failures on this vintage F-Series, and it wasn't due to a bad batch of alternators. The first failed alternator produces excessive heat in the alternator circuits, damaging the terminals in the connector between the wiring harness and the alternator. This damage produces excessive circuit resistance, which can trash a brand-new alternator shortly after installation, and the next one, and so on. Always inspect the wiring-harness-to-alternator connector for corrosion, distortion, and cracking before replacing a failed alternator. Ford's complete connector kit, part number E5AZ-14305-AA, can help. If this connection wasn't where you soldered and shrink-wrapped, if it wasn't done correctly, or if you did it after the current alternator was a goner, that may be where your problem lies. If everything looks right, take it to a technician with the appropriate charging-system diagnostic tools and wiring diagrams to figure things out. Tracking Down Vibrations
Q: My regular-cab 4WD 1999 Silverado vibrates and shudders when it reaches speeds of over 50 mph, which gets worse as speed increases. The tires are brand new, and balancing and alignment were done. The same thing occurred with the old tires. The symptoms stop when I let off the gas.   |   expert Truck And Suv Advice tracking Down Vibrations A: A highway speed vibration stopping when you let off the gas almost always indicates a problem in the driveline, as opposed to the wheels and tires--almost always. It can also be an unusual reaction to the changing load on a tire, wheel, or bearing, or a suspension problem not dampening normal vibrations as it should. You also want to determine if the vibration is coming from the front or rear. If it's in the front, you'll typically feel it in the steering wheel, and if it's based in the rear of the truck you'll feel it in the seat of your pants. Once you determine its basic location, inspect the applicable driveshaft and everything attached. Make sure the truck's ride height is correct and there isn't any crash damage that may have thrown the driveline out of line. Verify that the transmission and transfer-case mounts are 100 percent. And you may also want to have the driveshaft balance checked. Here's a list of other issues that may or may not be related, and you can check with your local Chevy service department for additional information. Some of the steel wheels installed on this line of GM full-size truck may be cracked, causing air-pressure leaks and vibrations. Wheel and tire out-of-round and radial force variation can cause vibrations and have a significant effect on ride quality, even though the tires (new or used) look good and balance correctly. Qualified shops have the equipment to diagnose and sometimes correct these conditions. There have been suspension issues on this platform that require replacing the steering rack (and a bunch of other stuff) to dampen normal road vibrations transmitted through the chassis. There also were problems with pinion bearings in the front axle locking up, causing vibration and smoke. Silverado Sensor Solutions
Q: In my 1996 Silverado (with the 5.7-liter), the SES light is either on continually or it flashes intermittently. The diagnostic tool says the engine's running rich. I've changed the plugs, wires, and air filter. What usually causes this issue? The forums I've read talk about a temp-control sensor, but if it's the same one that reports the engine temperature to the instrument cluster, that works just fine. A: The temperature-gauge reading on the instrument panel and the coolant temperature data received by the powertrain control module (PCM) come from two different coolant temperature sensors. So whether the gauge works correctly is irrelevant to how your engine's running. Trouble codes stored in the PCM's memory indicating a rich condition don't pinpoint the cause of a problem; they alert a symptom that needs to be further diagnosed--in this case, that there's too much fuel in the air/fuel mixture. A failed oxygen sensor can incorrectly indicate a lean condition, so the PCM will unknowingly send a rich command to the fuel injectors to compensate. The same thing goes for a coolant-temperature sensor reading incorrectly low, or a stuck open thermostat actually keeping the coolant temperature below normal--the system adds more fuel accordingly. If the sensors are fine, this is a genuine rich condition, such as a failed fuel-pressure regulator leaking unwanted fuel into the intake manifold. The injectors on the CSFI fuel system have been a problem area, and fuel regulators, oxygen sensors, and mass airflow sensors are known to fail fairly often, potentially inducing a rich condition. In your case, take the truck to a hands-on technician before going any further.   |   expert Truck And Suv Advice ABS Computer On The Fritz Abs Computer On The Fritz?
Q: The ABS and brake icons come on sporadically in my 1999 GMC Sierra SLE 1500 4x4. When I start the truck they come on, but if I shut it off and restart it they don't. Some days they won't come on at all, and other days they come on each time I start the truck. I've been to three mechanics: (A) My local GMC dealer cleaned the ABS sensors. That cost $400. (B) My mechanic friend said the ABS circuit board under the dash needed to be treated with a specific cleanser. That cost $340. (C) My brother's mechanic said the problem is with the on-board computer. He did some diagnostic work with his handheld unit and proclaimed it cured. It wasn't, and cost $200. Do you have any suggestions? All three said that when these icons are on, my ABS doesn't work. A: As a safety default, the antilock brakes won't function when the ABS warning indicator comes on due to a failure in the system. You still have fully functional standard brakes, though. In this particular system, the ABS and brake warning indicators are essentially wired together and controlled by the Electronic Brake Control Module and the Body Control Module. Go over the simple stuff first. Check the brake-fluid level and parking-brake adjustment. They can each activate one or both warning lamps. Low brake-fluid level in the reservoir is often an indication that your brake linings are worn and in need of replacement. Never top off the reservoir unless there's a known leak; if you do, there will be a major overflow when new pads or shoes are installed. There were numerous issues with speed-sensor corrosion and installation on this model Sierra, published in several recalls and TSBs, so that's an area to double check if all else fails. There have been instances of a loss of communication to the EBCM, the ABS warning indicator coming on, and various trouble codes being stored in the EBCM memory--all due to a poor ground connection. The EBCM is mounted under the truck, near the driver door on the inboard side of the frame rail, and the ground should be in the same area or further up near the front axle. The EBCM ground should be the terminal at the end of a heavy 12-gauge wire. Thoroughly clean the terminals and where they contact the frame, down to shiny metal. GM suggests reattaching them with a special new nut, bolt, and washer, then spraying it with undercoat. Also make sure the negative battery cable ground is clean and tight. How To Reach Alex
If you have a technical question regarding your pickup, SUV, or van, feel free to contact Alex, a master technician with the National Institute for Automotive Service Excellence. Send a letter to him in care of Truck Trend Garage, 831 S. Douglas Street, El Segundo, CA 90245, or e-mail us at trucktrend@sourceinterlink.com. Please include the VIN with your question. Due to the volume of questions received every month, we cannot guarantee that everyone's question will be personally answered or will appear in the magazine.

Can't wait for help with a problem you're having with your Truck or SUV? Ask the expert we trust here at Truck Trend Garage--visit Alex Steele at www.RealWorldAutomotive.com. Do-It-Yourselfer Advice
Q:Regarding the Q&A about the TrailBlazer with no air coming out of the air-conditioning vents: There is a fix for this problem, and it took me one hour to do after purchasing Kent Moore tool GE-47676, which pulls the mode door actuator. (The problem usually involves a random clicking noise from the actuator.) It requires a $40 actuator part, five screws, and the Kent Moore tool for $30 from eBay. I'm not a mechanic and I wouldn't call it a tough repair. Here's the rub for non-mechanic types: A dealer will charge $500 to replace this part because the techs will tear the whole dash apart to get to it. Why? Because the dealers don't know (or won't tell you) about a TSB that uses the new tool to eliminate the need to tear the dash apart, which would make the repair a mere $150. But the dealer usually won't mention the TSB. It's a total scam. A: GM only publishes warranty labor times--how much the automaker will pay a dealership technician to do a specific warranty repair. When a customer pays, dealerships and independent repair shops use outside sources for "cash" labor times, which are always significantly higher than warranty. The TSB specifying a reduction from 3.2 hours to 0.6 hour for HVAC mode door actuator replacement, thanks to the new special tool, is referring to warranty labor time. That same 3.2-hour warranty job would be closer to 5.1 hours in a cash labor time guide. Many folks believe cash labor time to be too high, but trust me, most warranty times are ridiculously low. Some outside labor time guides haven't been updated with the new mode door actuator replacement procedure and significant reduction in labor time. I don't know of many technicians who would object to a high-paying job if there's an established labor guide supporting the time, regardless of how long it takes him to complete the repair. There's a TSB on the new tool and labor time reduction, another on the appropriate GM service manual updates, and one more on the "mode door actuator clicking noise." Looks like a glitch has cost a few GM SUV owners some money. How Long For Gear Lube?
Q: I bought my GMC Sierra 2500 HD Duramax 4x4 with a six-speed standard gearbox new and now have 98,000 miles on it. Over the years, I always made sure the maintenance was done as per the owner's manual, but something bugs me. Nowhere in the scheduled maintenance does it talk about changing the gearbox oil. It covers the engine oil, coolant system, and all kinds of minor items, but it never talks about the standard transmission, transfer case, and rear and front differentials--and what about the power steering and hydraulic clutch? How many years can we go without replacing the oil in all these components? I understand they use synthetic oil these days, but are synthetics good for the life of the truck? A: I scanned through several related GMC pickup service schedules, specifically the Duramax diesel owner's manual supplements, and I see where you're coming from. According to General Motors, there's no need to change the six-speed manual-transmission fluid or the transfer-case fluid (unless you have an automatic), and you should periodically check or top off, but never replace, the front and rear axle fluids. Engineers believe that under normal operation, synthetic lubricants will hold up indefinitely, or at least for the predicted lifespan of the truck. The advanced lubricity and thermal resistance of synthetics outweigh those of petroleum-based products, and the manual transmission, transfer case, and axles are sealed (or nearly sealed) components which limit or eliminate incoming contaminates--such as dirt and normal blow-by gases into engine oil. Drivetrain technology also has lightened the load on lubricants by reducing internal friction. As far as brake-fluid, clutch-fluid, or power-steering-fluid replacement, nowadays they're not typically part of a manufacturer's maintenance schedule. With all that said, if it's my truck and I want to keep it for a long time, I wouldn't want any drivetrain fluid to go far beyond the 100,000-mile mark. Of course, this is my opinion. If you agree, be sure to use the correct replacement fluids. There may be updates since your owner's manual went to print. And it's common practice for dealership service departments' maintenance schedules to differ from those of the manufacturer. Dodge Ram Idle Drop
Q: I bought a new 2008 Dodge Ram with the 4.7-liter V-8 and a six-speed manual transmission. When I shift, the electronic throttle maintains the rpm for two seconds or so. It doesn't return to idle rpm between shifts. Can this be adjusted? It's annoying and hard on the clutch. Also, why do manufacturers put such light springs on throttle pedals? I always have to add a heavier one. A: I've heard similar comments in reference to manual transmission shifts in Electronic Throttle Control-(ETC) equipped trucks. I relayed the question through Dodge communications to one of their powertrain calibration engineers. According to Dodge, engine speed not dropping down to idle immediately after letting off the gas between shifts is due to a 200-300 millisecond delay between your foot and the electronically controlled throttle plate. Interestingly enough, in this situation, a long cable with a springloaded throttle body at the other end is faster than the latest drive-by-wire technology. Dodge's engineer stated, "We [the engine systems community] have implemented a few things to help this problem, but it cannot be completely eliminated. It's just the nature of ETC." He also indicated that driving style determines whether this delay in throttle response is seen as an issue. There's no way around the problem with your truck at this point but, if technological trends hold true, these systems will get faster as time goes on. It appears ETC advantages outscore this glitch in driveability. Electronic throttle control enables traction control, stability control, and cruise control, and assists in additional powertrain control functions. Example: ETC is being incorporated in the reduction of driveline "clunk" (a common question sent to "Truck Trend Garage") by cushioning the contraction of driveline slack with controlled on- and off-throttle application. As far as the spring tension at the accelerator pedal is concerned, that's a personal preference. I'd imagine engineers are attempting to keep ETC pedal tension similar to what we're used to with a cable and standard throttle body. I don't see any danger in adding a heavier spring at the pedal. Then again, you never can tell. Electric Vs. Clutch Fans
Q: Why don't common truck manufacturers use electric cooling fans for pickups instead of the clutch fans? I could see having the clutch fans in addition to the electric fans as a necessity if an owner wants to do a lot of towing or heavy hauling, but if the government is getting serious about the fuel mileage issue, then electric cooling fans would be a good start. I have one more question: I'm thinking about purchasing a different pickup. I'm looking at a Sport Trac 4x4 with the 4.0-liter V-6. Would it void the factory warranty if I took out the clutch fan and installed either a large single or a double electric cooling-fan system? They've been using these fans in passenger cars for quite some time with much success. A: I spoke with the technical department at the automotive division of Flex-a-lite Performance Cooling Products, which designs and manufactures electric and belt-driven coolant-fan systems. According to Flex-a-lite, the number one reason you see mostly clutch fans on truck applications is capacity. The size, pitch, location, and torque of a belt-driven fan bolted to a water pump will outperform an electric fan fixed to the radiator. The cost of speed-controlled mechanical clutch fans is lower, and overall system durability and reliability are greater. Trucks aren't always used as designed, but they are built for heavier-duty applications than passenger cars. When we're talking power and fuel economy, yes, the belt-driven fans will cost you. In some applications, going by Flex-a-lite's product testing, you can save as much as 15 horsepower by switching to a complete electric coolant-fan system. If power gains count but cost doesn't, then why not make the switch? Will you make up for the money spent on the electric fans with cash saved at the pump? I'm not so sure. And if you're a serious four-wheeler, you may side with the durability of the belt-driven setup. About the 2008 Ford Sport Trac: It does use a belt-driven fan, but did you know that its fan-clutch is electronically controlled by the engine's PCM? This makes the system more efficient by taking into consideration temperatures of the engine coolant, oil, transmission fluid, and intake air, and air-conditioning status, before commanding the appropriate fan speed. Just installing an electric coolant fan shouldn't void the manufacturer's warranty, but if the system ever failed and caused engine damage, you're buying the engine. And dealing with the new Sport Trac, disabling the electronically controlled fan may turn on the "malfunction indicator lamp" light, set a trouble code, and affect the overall efficiency of the powertrain control system. I wouldn't mess with it.