BACKYARD MECHANIC: Dishing the dirt on fuel-injection cleaners

Hey there, time traveller!
This article was published 05/11/2010 (5538 days ago), so information in it may no longer be current.

QUESTION: One item you have touched on in the past, but to my memory, not specifically this question, is additives — fuel-injector cleaners. I’ve received conflicting opinions on the matter even from reliable sources. Our gasoline has a blend/mixture of ethanol, up to a 90/10 per cent. I have been told it is not necessary to add fuel-injector cleaner as the ethanol acts as a cleaner. I generally added the fuel-injector cleaner just prior to an oil change (applied the cleaner at every 4,500 kilometres). May I have your view on the matter, please? — Don

ANSWER: Ethanol will clean out the varnish and gunk inside a gas tank, which can then plug fuel filters, but doesn’t really clean dirty injectors. Dirty injectors are not really plugged with dirt. Rather, they become gummed up and sticky so they don’t open and close properly or spray the fuel in a fine mist. The gum deposits are formed as liquid fuel at the injector tip evaporates when the engine is shut off, leaving varnish behind.

Vehicles that operate mainly on the highway have higher fuel-flow rates through the injectors that help keep injectors clean. Slow-speed driving, idling and short trips will cause deposits to build faster. Gasoline does contain injector-cleaning additives, but many contain only the minimum amounts specified in the standards. Others contain much more. Shell fuel, for example, contains three times the minimum specified amount of injector-cleaning additive in their fuel.

Even so, there are times when adding fuel injector cleaner to the gas tank can be beneficial. If your fuel economy starts to drop, if the engine takes more cranking to start, or if you feel a slight hesitation when accelerating, you may benefit from adding an additive to the fuel tank. One container of additive to a full tank of fuel is enough. Don’t add more, as too high a level of cleaner additive could damage fuel-system parts. You can add some with each fill, or only occasionally. Some owners never add any and rely on the additive in the fuel.

Driving patterns, engine design and fuel-system design all have an effect on the amount of injector deposits that form. Concentrated injector cleaner can be run through the injectors using professional equipment at repair shops, and sometimes this is necessary if the injectors are badly gummed-up, but adding some to your fuel tank on an occasional basis will help keep them flowing properly.

QUESTION: I have a ’02 Monte Carlo with a “whump-whump” noise in the front at 60 to 70 kilometres per hour. It has a V6 engine. When I turn left the sound goes away. Turn right and it gets louder. The ABS light and traction-control lights are on in the dash. An OBD 2 scan tool says “no trouble codes stored in the computer.” I replaced the right outer tie rod, had a four-wheel alignment and replaced the right wheel bearing-hub assembly. It still has all the same symptoms. Any advice? — David

ANSWER: The symptoms sound like a wheel-bearing problem. You were on the correct track when you replaced the right wheel bearing, but you should have replaced the other side. You should think of the load changes on the vehicle during a turn to diagnose this problem. When you turn right, the weight transfer is towards the left side of the vehicle, placing more load on the left wheel bearing, and the noise gets louder. When you turn left, the weight transfers to the right side of the vehicle, taking the load off the left wheel bearing, so it becomes quiet. Replace the left wheel bearing and the noise should be gone.

As for the ABS and traction control warning lights, a bad wheel bearing can cause an irregular wheel speed signal. This will cause the warning lights to come on but not necessarily set a code. If you are using an OBD2 code reader, most only read emissions codes, not ABS codes. You need a scan tool that will read ABS systems to see if there are any codes in that system. When you fix the wheel-bearing problem, the wheel speed signal problem should be corrected, too, and the warning lights will go out the next drive cycle.

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

kerr.jim@sasktel.net