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Respect The Tech: When Art Does Not Reflect Real Life

We are an industry very focused on our own image. But, sometimes we need to step back to get a global perspective on the issue. Shutterstock.com is a website where photographers can sell stock photographs online for magazines, advertisements and billboards....

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Consistently Selling Maintenance Boosts Customer Satisfaction, ­Retention

While seasons change, your maintenance strategy should be consistent year-round. For this edition of ­Maintenance Chronicle, we take a snapshot of the maintenance sales of an 11-bay shop in ­upstate New York during a two-week ­period. What did...

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Documenting Inspections: Are You Leaving Maintenance Dollars On The Table?

How do you translate scribbles on a ­repair order into sales? There is no magic trick involved — the key is to document the vehicle ­inspection process. The more you know about your customers’ vehicles, and the more you are able to document...

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Audi: Transmission Does Not Shift Due To Cabin Air Filter

Model: 2001 Audi A6 Avant Quattro, 2.8L Complaint The customer states the transmission does not shift. Cause Confirmed the customer’s complaint and found the transmission did not shift. Inspected the automatic transmission fluid level and condition...

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Kia Driveability Diagnostics: Chasing Intermittent Gremlins

This month, we find ourselves looking at a 2004 Kia ­Sorrento that the owner says is losing power and stalling with no established pattern. It will run well for days or even weeks at a time without a problem, only to then act up without warning,...

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Mercedes-Benz: Noise in Front of Vehicle/Dash Area

Affected Models: Model 203.052/054/092/056/087 Model 209.356/365/372/375/376/377/456/ 465/472/475/476/477 If you receive customer reports of noise from the center of the dash area in the above-listed vehicles, this may be caused by a portion of...

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Ford: Low-Speed Strut Noise

MODELS: • 2006-2009 Fusion • 2007 Zephyr • 2007-2009 MKZ • 2006-2009 Milan Some vehicles built before 8/5/2008 may exhibit a popping, rubbing, grunting, squeaking, crunching or creaking type noise from the front strut mount when going over...

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Honda Civic Alignment Spec: 2006-'11

Built on a high-rigidity unit-body platform, the 2006-2011 Civic has a MacPherson strut front ­suspension and a multi-link rear suspension. The eighth generation switched from a high mounted to a low mounted steering rack and significantly increased...

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False ABS, ESC Activation Causes and Cures

The first mass-produced anti-lock braking systems (ABS) were introduced in 1985. By 2008, almost every passenger vehicle came standard with ABS. Next, electronic stability control (ESC) became a mandated safety feature for the 2012 model year. Along with...

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Equipment and Tool Institute Launches an Important Market Research Study on New Car Buying Preferences of Consumers

In an effort to assist its members in having the latest market information and bringing new and improved equipment and tools to the marketplace, The Equipment and Tool Institute (ETI) has launched a series of Market Research Projects. The current...

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Redline Detection Names 2015 Redline Rock Star Performance Award Winner

Redline Detection has announced the winner of its 2015 Redline Rock Star Performance Award. Rob McNees of Truck Centers, Inc. (TCI) was selected by the Redline Technical Advisory Board as the winner and received more than $4,000 in cash and prizes from...

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Rivet Bonding Comes Full Blast

By Mitch Becker for BodyShop Business   By now, most of you have heard the news that Ford has mainstreamed rivet bonding with the introduction of the 2015 F-150. This has forced many shops to look into some new equipment, such as self piercing...

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Home Engine Diagnostic Dilemmas: Servicing Quadrajet Carburetors

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src=”/wp-content/uploads/Articles/05_01_2008/39766Carb4jpg_00000021239.jpg” border=”0″ ” align=”right” alt=”photo 4: float level can easily be measured on the quadrajet.”/>can be measured by inserting a special Kent-Moore float level gauge into the bowl vent located just aft the choke valve. See Photo 4.

Measuring the distance from the top of the bowl vent to the float and then subtracting the dimension from the bowl vent to the cover gasket can also determine the float level. If a repair manual with adjustment specifications is available, refer to the float level specifications listed for the model number stamped vertically on the driver’s side of the carburetor main body or on a tab attached above the primary throttle shaft. Although most Quadrajet float levels are set at 3/8”, the specification can vary from 5/16” to 1/2”.  Last, the metering rod piston can stick in its photo 5: metering rod travel can be easily checked by inserting an applicable tool into the front float bowl vent. bore, causing a lean air/fuel condition. The metering rod travel can be checked by inserting a screwdriver or punch into the bowl vent hole in front of the choke valve to see if the metering piston spring returns the metering rods to a raised position with the engine off. Spraying some penetrating oil into the bowl vent and tapping on the metering rod hanger with a screwdriver or punch can often loosen the metering rods. See Photo 5.

Quadrajet Adjustments
  The Quadrajet has a number of critical adjustments that make it perform better. The initial adjustment for idle mixture screws on most Q-jets, for example, should be lightly seated and then photo 6: metering rod travel can be easily checked by inserting an applicable tool into the front float bowl vent. backed out three turns. Initial idle speed can be obtained by seating the primary throttle plates and then turning the idle speed screw in about two turns.

photo 7: the secondary metering rod height adjustment should be checked to ensure delivering a correct secondary air/fuel ratio.Primary jetting is most easily corrected by increasing the jet size in two-step increments. To remove the primary metering rods, lightly tap the metering rod hanger with a screwdriver handle. Spring pressure will pop the plastic retainer from the main body casting.

  Before installing any Q-jet, make sure that the secondary throttle plates are seated and that the secondary throttle linkage is adjusted to specification. A tab on the primary throttle shaft actuates the secondary linkage. This tab determines the open position of the secondary plates. When the tab contacts the secondary linkage, the linkage pushes against the upper part of the secondary throttle shaft lever. At that point, the linkage should be located mid-point in the slot located below. See Photo 6.

photo 8: use a 3/32” hex wrench to loosen the lock screw on the air valve spring preload adjustment. On the topside, the secondary metering rod hanger should be adjusted to ideally achieve equal metering rod height and to allow both metering rods to touch the bottoms of their respective wells. This adjustment is done incrementally to avoid binding the rods in their hanger and to avoid damaging the hanger itself. See Photo 7.

 Secondary air valve adjustment is critical to Quadrajet performance because correct secondary air/fuel metering requires a constant depression or vacuum in the secondary venturis. If a repair manual with adjustment specifications is available, begin with the applicable spec. If a specification is not available, preload the air valve spring adjustment one-half turn, Photo 9: Make sure the secondary throttle lockout disengages when the choke valve opens.  then road test the vehicle. If the engine stumbles as it accelerates, increase the spring preload in one-half turn increments until the stumble disappears. See Photo 8.

Last, always make sure that the choke valve lockout is allowing the secondary throttle plates to open. Some Quadrajet models incorporate the lockout at the upper choke housing linkage while others locate the lockout  at the secondary throttle shaft. In either case, the choke valve linkage keeps the air valves closed until the engine warms up. See Photo 9.

Quadrajet Wrap-Up
When serviced correctly, the Quadrajet will prove to be a very responsive and economical carburetor to use for many street driving and racing applications. Although Quadrajet is very dependable, it pays to clean the external choke linkage and air bleeds with an aerosol cleaner. When changing the fuel filter, remember to replace the plastic gasket located on the end of the fuel inlet housing before reinstalling. Cross threading the inlet housing can be greatly reduced by cleaning and oiling the housing threads before installation. If the threads are seriously damaged, aftermarket kits can be used to replace the factory housing. In virtually all cases, a well-maintained late-model Quadrajet will maintain exhaust emissions within legal limits for collector and street rod vehicles while providing a full-bore performance experience.

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Gary Goms

Gary Goms is a former educator and shop owner who remains active in the aftermarket service industry. Gary is an ASE-certified Master Automobile Technician (CMAT) and has earned the L1 advanced engine performance certification. He also belongs to the Automotive Service Association (ASA) and the Society of Automotive Engineers (SAE).
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