Finding the Right Balance Q:My problem is with a '96 Chevy S-10 2WD six-cylinder pickup. There's a vibration in what appears to be the rear of the truck. It becomes noticeable between 60 and 75 mph. First, I had the tires balanced on the vehicle (I was told this is the best way to balance tires). The vibration was still there so I replaced the driveshaft center-support bearing and had the driveshaft balanced while it was out. After all that, the vibration was still there. So here I am $200 into a problem that seemed to be as simple as an out-of-balance tire.
A:There's a great tool out there that may be a necessity in accurately diagnosing your problem: The little lady is known as EVA (Electronic Vibration Analyzer). It's a mandatory tool in a GM service department (J-38792-A) and is manufactured by SPX Kent-Moore Corporation (they should have the part, if your local dealer doesn't). The EVA is an electronic device that can pinpoint the cause of an automotive vibration with the use of vibration sensors placed in the appropriate locations. You can then take it one step further with EVA's ability to balance a driveline when required. Your truck's vibration may stem from a number of different areas. For example, someone may have previously replaced a pinion seal on the rear axle and caused the problem. If the pinion yolk wasn't marked to the pinion shaft before removal and reinstalled in its original position, the assembly may have been thrown out of balance causing a driveline vibration. Improper driveline angles due to chassis damage or improper ride height could also produce a similar condition. Other possibilities include an out-of-balance brake drum, a bent axle, and tires or wheels out of specs even though balancing correctly. Finding a dealer with the proper tool and a technician who knows how to use it should be your next step.
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Half-Ton GM Tranny Gauge Q:I own a 2000 Silverado 1500. It's a great truck, except for one missing item: a transmission-temperature gauge as on the 2500 and 3500 models. From what I've been told, it's an easy change. I can purchase a new, standard instrument panel from GM for a 2500 or 3500 Silverado with the tranny-temp gauge. I'm told the replacement is easy. Then I can have the dealer flash the computer so the truck recognizes the new gauge. Will my truck retain its current mileage? Is the new transmission-temperature gauge a glorified dummy light like the engine-temperature gauge? I don't want to go through all this work and expense if all it's going to tell me is that it's cold, medium, or hot.
A:Mileage memory is stored within the instrument-panel assembly, so whenever you purchase or exchange a "cluster," it has to go through an authorized supplier to recalibrate and maintain the accurate odometer reading. I contacted an authorized General Motor's electronics service provider regarding the swap of the Silverado instrument cluster. The 1500 should have all the appropriate wiring, sensors, and computer programming to support a 2500 or 3500 series instrument cluster equipped with the transmission-temperature gauge. The folks I spoke with have done the job before without having to perform any recalibration of the powertrain-control module. However, the safe way to go before ordering any parts is to ask a Chevy service department to plug in the Tech II scan tool to confirm the presence of transmission-temperature data. The factory gauge is only going to offer minimum accuracy, which is all you need on the highway. As opposed to cold, medium, and hot, most read 100*, 200*, and 300* F. For more precise readings, go with a high-quality aftermarket mechanical or electronic gauge setup from a manufacturer such as Auto Meter Products Inc. (www.autometer.com; 815/895-8141). It can supply you with a quality product at a good price, but you'll lose the factory finish you wanted to maintain.
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The Truth About Parts Q: An independent auto-repair shop replaced the fuel pump on my '96 Chevy Suburban. The new pump was obtained from the Chevy dealer (so we wouldn't have a problem with an aftermarket pump). It turned out to be bad. GM will replace the pump, but will not pay for the redo of the repair unless the job was originally done in a GM shop. I believe it would be a service to your enthusiastic customers to let them know of GM policies, which attempt to steer repairs away from independent repair shops and into the dealership. It's unfair for the customer to have to pay twice for the labor. It's also unfair to expect the independent shops to redo the job without pay. I know that you depend on advertising from auto companies to pay the bills, but you also have an obligation to subscribers to let the truth be known.
A: There's an age-old rule in the automotive-repair industry: the replacement of a defective part, under the part- manufacturer's warranty, doesn't normally include reimbursement for additional labor hours. This, of course, only applies to vehicles no longer under the original manufacturer's warranty. The use of an aftermarket fuel pump in your situation wouldn't have helped because that manufacturer would have also refused to pay labor costs. It's common business sense when you look at all the variables, a chief factor being the strong possibility of misdiagnosis. The first thing that comes to mind when told of a brand new Delco fuel pump that was just installed and doesn't work is to evaluate all other possible causes of the problem. There could be a bad relay, fuel regulator, and so on. There are also circumstances where parts become damaged during installation. When the job is performed at the dealership, and it's confirmed to be a defective part by a GM-trained technician, the labor can then be performed under the manufacturer's warranty on a case-by-case basis. Common sense, once again. I don't see this as a tactic in steering clientele. Keep in mind there's another unwritten law in many quality repair shops, whereas they'll traditionally absorb the loss in repeat labor to replace a defective part. Let's say a similar situation occurred at a Chevy service department after the installation of an aftermarket part. There's a likelihood they'd cover the labor cost if the part turned out to be defective. The expense would, most likely, come out of the service department's and/or technician's pocket in order to maintain customer satisfaction.
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Unsteady Ram Acceleration Q:I have a '98 Dodge Ram, short-bed quad-cab with a V-8. Occasionally, when I take off, the rpm is unsteady. Once I'm in second gear, it's fine. Until then it bounces up and down, slightly, but enough to notice. And, in case you were wondering, my foot is steady. I've checked.
A:There's a wide range of suspect areas to investigate. This includes the engine and transmission. The first place to start is the elimination of faults that have plagued the Magnum engines installed in '94- to '99-model-year Dodge trucks. First, perform the ignition-wire routing modification. The original positioning of the wires form the assembly line that resulted in a crossfire condition, which produces symptoms such as spark knock, various single-cylinder misfire, and/or a surge. Confirm the notorious intake-manifold plenum pan gasket hasn't failed and caused an internal vacuum leak. The symptoms may be one or all of the following: excessive oil consumption, spark knock, misfire from oil-fouled spark plugs, and the check- engine light coming on. The folks at the dealership or any qualified repair shop should be familiar with the repair procedures if these conditions are relevant. After that you'll have to take it step by step down the diagnostic tree.
Transmission Second Gear Shutter Q: I have an '02 Chevy Silverado with about 20,000 miles on it. When shifting between first and second gear, it shudders. The warmer the truck gets, the more and harder it shudders. I took it to the dealership, and it's putting in a new wiring harness from the alternator to the transmission. Have you heard of this problem before? Will the wiring harness fix it?
A:The repair won't require the replacement of a complete wiring harness, but does involve a new connector along with the repositioning and addition of a few wires on the alternator circuit. It seems that the electrical feedback involved with the original routing of the charging circuit interfered with the operation of the transmission-pressure control solenoid. This resulted in a fluctuation in line pressure and produced the shudder from first to second gear, which brought you into the service department in the first place. Chances are it did a quick test to corroborate the diagnosis by simply disconnecting the alternator and taking a test drive to confirm the elimination of the 1-2 shudder. The condition may affect certain '01-'03 Chevy Silverados and GMC Sierras and is documented in Chevy Technical Service Bulletin 02-07-30-030.
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Sticky Throttle Buildup Q:I own an '01 Dodge Ram 1500 4x4 pickup with a 5.2-liter V-8 engine, automatic transmission, and approximately 58k miles. The throttle has been sticking open for less than a few minutes each time. Finally, it stuck open longer, and I took it to a local Dodge dealer to see what was causing the problem. They found a buildup of carbon on the inside of the throttle body and advised me that it could be cleaned to eliminate the problem. Everything seemed fine for a few months until the throttle stuck open again. I took it back to the dealership, and they had to clean the throttle body again and also replace the IAC motor. What can be done to take care of this permanently?
A:Excessive carbon buildup within the throttle body is a common event that can almost be considered a normal maintenance item. The carbon may prevent the throttle plates from seating properly in the idle position and therefore result in a higher-than-normal idle speed, which is ordinarily controlled by the powertrain-control module. I don't see how an undue amount could have accumulated in such a short period of time and require another cleaning. A faulty IAC (Idle Air Control) motor is another possible cause of an intermittent high idle, and perhaps its replacement the second time around has corrected the problem. The IAC is a computer-controlled valve that varies the amount of air bypassing the throttle plates in order to regulate idle speed. If the condition reoccurs I'd suggest a detailed inspection of the throttle body assembly, springs, linkage, the throttle cable, and anything else that may have prevented the full seating of the throttle plates. Abnormal wear of the throttle body itself is a possibility that would require replacement of the entire assembly. Of course, there are lots of other potential causes, ranging from a vacuum leak to an intermittent data sensor signal causing the PCM to raise the idle speed at incorrect points in time.
Two for the Price of One Q:Why does my '96 Ranger with the 2.3-liter I-4 have eight spark plugs? No one seems to know.
A:The Ford "Dual Plug" 2.3-liter inline- four-cylinder engines have been standard equipment in the Ranger since '89. The twin-plug-design cylinder head is used to increase the efficiency of combustion. This provides a faster burn by starting the combustion process from two different angles within the combustion chamber. The result is better performance with maximum fuel efficiency. The system utilizes a distributorless ignition system comprised of two separate four-post coil packs. The system also incorporates a dual-plug inhibit. This limits firing to only the four spark plugs on the right side of the engine during startup and then switches to dual-plug mode after ignition. Similar combustion chamber designs have been used by Alfa Romeo and Mercedes-Benz. Honda has just come out with new 1.2-liter and 1.4-liter engines utilizing a technologically advanced i-DSI (intelligently controlled Dual and Sequential Ignition) system based on the dual-plug combustion chamber.
How To Reach AlexIf 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.
