BACKYARD MECHANIC: Cold-air intake may not be such a hot idea

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This article was published 08/06/2012 (5108 days ago), so information in it may no longer be current.

QUESTION: I am working on a 2004 Pontiac Grand Prix with a 3.8 V-6. It has 145,000 kilometres on it. I put magna flow mufflers on it last year, and I was told it would be good to put a cold-air intake on to allow more air into the engine. My question is, will that affect the way the mass airflow sensor works and will it help my fuel economy? I have an old cold-air intake pipe that is three inches in diameter and a Ractive cone filter I can modify to fit, but I don’t want to mess anything up. I would appreciate your thoughts on this matter.

 

ANSWER: A cold-air intake will work with your mass airflow sensor, as the sensor measures mass of air — not just volume. Cold air is more dense than warm air, so it will give you more power, but only if you are demanding power such as full-throttle conditions. Under cruise conditions it will make only a slight difference in power and virtually no difference in fuel economy. One thing the factory engineers design into the factory air cleaner is a water-separation system, so water won’t enter the air intake during normal operation, such as driving in heavy rain or splashing through an average puddle. Consider this when installing a cold-air intake system. If enough water enters the engine, it can destroy the engine in a single revolution. Place your intake so water can’t get in easily, but remember, placing the air intake in the engine compartment allows it to pull in warm air. Installing a modified intake system is always a compromise.

 

QUESTION: I have a 2006 Pontiac Grand Prix with about 128,000 km. My car’s ABS kicks in sometimes on dry pavement and stopping while turning left (parking in a spot for example). I noticed the problem for a week. The problem started when I plugged in the carMD my dad ordered from TV as well as it read a pending code U1000. Please help me as I am worried since this is my daily driver.

 

ANSWER: The pending code U1000 indicates that there has been a communications error between computers on your vehicle. It is listed as a “pending” code because the problem has occurred once but has not occurred again and has not turned on the MIL (Check Engine light). I am unfamiliar with the exact protocols for the carMD device when communicating with the vehicle computers. The carMD is a code reader that will display trouble codes. Often, these devices will take priority over message traffic on the data lines between other modules and this can cause a communications error code to show. It isn’t a problem, other than the code should be cleared.

You don’t mention an ABS or Red Brake warning light on, so I will assume they go out as they normally would after startup. If there were a communications error from the ABS module, these lights would be on, so I don’t think the U1000 code has anything to do with your ABS activation problem.

The most likely cause of your ABS activation is the drop out of a signal or an erratic signal from a wheel speed sensor. The front sensors are the most common problem area. The wiring for these sensors flexes as the wheel travels over bumps and it twists when the front tires are turned for corners. A code may not be set for the particular sensor that is at fault because the erratic signal occurs for such a short time period that it is interpreted as a wheel locking up. The ABS then activates prematurely.

A scan tool can be used to monitor the wheel speed sensor signals and detect an erratic signal. As the problem gets worse, eventually a code will be set and then the code reader can direct you to the problem area. You can take the car to be scanned at a repair shop, but you may also be able to see the problem on the ABS sensor wiring harnesses. Look for rubbed or chaffed marks on the sensor wiring inside the front wheel wells. The wires can’t be repaired so the faulty wiring or sensor would have to be replaced.

 

Jim Kerr is an experienced mechanic, instructor of automotive technology, freelance journalist and member of the Automobile Journalists’ Association of Canada.

kerr.jim@sasktel.net