Tom's Corner Garage: Stalling When it Rains
This weekly feature for Edmunds Daily about car repair and maintenance is written by Tom Torbjornsen, the popular host of America's Car Show on satellite radio.
Dear Tom,
I own a 2003 Ford Focus with a 2.3L engine that stalls (and sometimes shuts off) when it rains hard, so I took the car to my dealer. They told me it would cost $95 an hour for diagnostics and a whole day for the technician to find the problem! Needless to say, I drove the car back home. The job would cost me several hundred dollars or more and that's not including the parts. I need your advice!
Lynda from Wilmington, DE
Lynda should try spraying water on the sparkplug wires with the engine running. This should duplicate the conditions that cause the engine to stall. If it stalls then you know the wires are bad and need to be replaced. Also, take the car to another dealer. The price you were quoted is way too high.
What causes spark plug wires to go bad?
When the spark plug wire insulation gets old and worn from heat exposure, moisture is allowed to penetrate the wires and cause cross firing when it's wet outside. Wires that lay close to each other tend to exchange voltage, which results in cross firing.
Why does Lynda's car stall only in the rain?
When excessive environmental moisture is present electrical problems tend to crop up because moisture provides an easy path to ground for a voltage leak. That's the reason why electrical plugs are sealed from the factory with dielectric grease or silicone, to protect against moisture. My suspicion is that Lynda's car has bad spark plug wires that are cross firing when it's wet outside.
Can I test this theory myself?
Yes. Wait until dark and then raise the hood. With a spray bottle in hand, start the engine and spray water on the wires. If they're leaking, you will see sparks jump between the wires. It will be quite an entertaining light show.
$95 an hour and a whole day for a tech to find the problem?!
If we found ourselves in this situation, we would question the service writer because, according to Ford's diagnostic labor outline (below), a pinpoint test of each component or circuit of a system takes four-tenths (0.4) of an hour. In addition, if a repeat final quick test is performed, it takes another two-tenths (0.2) of an hour. And a road test takes a half-hour (0.5). These quotes are for the services of a skilled Ford Tech. Sounds like Lynda better find another shop. Even if the shop charges an initial hour's worth of labor in addition to the costs quoted in the table below, the charges would still be significantly less than what she was quoted.
Can I change the spark plug wires myself?
Yes. Buy a set of wires for your vehicle/engine application. Then change one wire at a time, measuring each new wire against the old ones to make sure you have the correct length. Also make sure you only pull one wire at a time to make sure you plug into the correct voltage tower on either the distributor cap or coil. And success to you!
'Til next time...Keep Rollin'
- Posted by
- Ron Montoya October 28, 2009, 11:00 AM
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- Car Maintenance
Glad to see you guys included a section from the Ford labor guide.
Part of me would be tempted to take that excerpt to the Service Manager and ask him/her why it takes their techs 8 hours to do the same diagnostic. In reality, unless I otherwise felt good about that dealership, I'd be tempted to take my business elsewhere. I'd definitely take it to another Service Adviser.
Lynda, while it's a great place to start, it's not certain that that's the cause of your problem. At the same time, changing the wires is inexpensive and not a bad thing to do anyway. Certainly worth a try. If you haven't already, replace the plugs too.
The internet is full of instructions on how to do it:
http://www.ehow.com/how_4484618_replace-spark-plugs-ford-focus.html
If you don't feel comfortable doing it yourself, any trusted light duty shop can easily handle the task.