Drive it forever: Starting procedure can prevent problems

Dear Mike: In a recent column, you mention that warming up a car fully before driving it isn’t necessary. I agree with this completely, but I disagree with your statement that “Shutting down an engine that hasn’t reached operating temp will have zero short-term effect.” My experience with two cars (Nissan Sentra and Ford Focus) has been disastrous when I shut down these cars after running them for less than one minute and then starting them up some time later. Both cars flooded severely, even though they’re both fuel injected. The cars had to be towed away and undergo a ton of service. If you think about it, it’s pretty hard to flood a fuel injected car, no?

A: Unlike carbureted cars that generally required a single press of the accelerator pedal to set the choke, injected cars are usually best started by not touching the pedal at all.

Fuel-injected cars normally have a regime called “clear flood” mode built into their firmware. If the car is flooded (which, as you say, is tough to do), depress the gas pedal all the way to the floor. This tells the computer to crank the engine with spark but without pulsing the injectors and injecting any fuel. When the engine starts on the excess fuel, simply remove your foot from the pedal and release the key.

The issues with both your cars sound more like one or more leaky injectors. Start up the engine, and immediately shut it down and the fuel in the rail and accumulator can drain down into the cylinder, and then past the rings into the crankcase. If the engine is warm, the fuel will vaporize instead of draining as droplets. The fuel vapor will then be trapped into the engine’s evaporative emission system and purged the next time the engine is started and warmed up.

Dear Mike: I have a 1996 Explorer, and yesterday its anti-lock braking system light came on, and it won’t go off. What is causing this?

A: This is a classic type of question that I get. I’d like to answer: “I have no idea.” But I won’t.

Here’s a question for you: How long is a piece of rope? Tough to answer that one, eh? It’s the same with your question.

The ABS light is on because the ABS controller has determined that something is wrong. Actually, that’s not correct, come to think of it. The ABS controller is getting data from one of its sensors that it doesn’t know how to interpret. Your vehicle has four tone wheels, mounted on the end of the axles that look like gears, and a sensor is mounted next to these wheels. These sensors count the teeth on the tone wheels to tell the ABS controller how fast the road wheel is rotating.

So, a) a tone wheel could be missing some teeth; b) a sensor could be bad, or improperly adjusted; c) the wiring to the sensor could be broken or shorted; d) there might be some internal problem in the ABS controller’s solenoids or pumps (like a hydraulic pump that has failed and doesn’t respond when the controller does its power-on self test when you turn on the key); e) or 30 or 40 other things.

What you need to do is to find a mechanic who has a scan tool that can interface with your ABS controller and have him poll the controller for the error code. The error code will at least tell you where to start looking.

Dear Mike: Are fuel additives a waste of money? I think Sta-bil works, but what about the others — the ones that claim to “clean” the carburetor and valves and give you better mileage and enable the fuel to burn more efficiently? Have you, or anyone you could direct me to, done any testing on this?

A: Sta-bil is one brand of additive intended for engines (lawnmowers and chain saws and other stuff that go into storage). There are others, and I recommend using them. Sta-bil sure keeps the carburetors in my Ducati from gumming up over the winter.

Fuel injector cleaner (I prefer Chevron’s, but STP and a couple of others are good, too) can restore some performance and mileage if the fuel system and injectors are dirty.

For diesels, you should use an anti-gelling additive during cold weather to keep flakes of wax from clogging the filter.

But any additive that claims to improve mileage or performance — beyond what it was when the car was new — won’t.