Hello all,

I have a 2007 Mazda 6, 4 cylinder, abt 30k miles. I bought it new in May 2007 and began having a somewhat obnoxious problem starting April/May 2009.

If I let the car sit all day in the sun (or possibly just with hot temps), the car will fail to start. I turn the key a little bit and I get electrical power and can open the windows, run the fan, play music, etc. I turn the key farther to start the ignition process and hear the first part of the startup (a sputtering sort of sound) as long as I keep the key turned - but the engine fails to start.

I've tried to fix and workaround this problem, but it persists and is obnoxious. Here's additional information.

The problem doesn't occur if the dash thermometer reads about 82 deg F or below (the dash thermometer doesn't really report ambient temperatures correctly and reads high temperatures after sitting in the sun). I'm guessing the threshold temp for this to occur is 83 or 84 deg F.

If I put my fan on high for 3 to 10 minutes, I can almost always get the car started eventually. 3 mins is if the temperature is lower. Today the car temperature reading was 92 degrees and it took 7 mins of running the fan before I could successfully start the car.

I've tried using fuel line cleaner with no success. Still happens on empty and full gas tanks.

I've taken the car to the dealer, but they haven't been able to duplicate the problem (presumably because once whatever cools off, it takes quite a while to heat up again). So, under cool temperatures, this problem is impossible to find with whatever current diagnostics techniques mazda dealers use.

Anybody have an idea what is wrong?

Thanks

 

How about a new battery? My battery on my 06 mazda6s was last less than 2 years. I am not sure the battery on 4 cy is same as v6.

 

I have considered the battery and I don't think I can rule it out entirely. However, if the battery were failing, it would seem strange that it fails in warm weather instead of cold and has been failing for such a long time. Also, the electronics such as windows, radio, and fan work just fine all the time.

 

Have a load test done on your battery. If it is still the Mazda OEM battery in your car, those have been known to be junk.

-Sheldon.

 

The battery failed the load test so I bought a new one. That means my battery lasted for less than 3 years - miserable reliability. I haven't had any recurrence yet but it hasn't been hot out either so I'm hoping this took care of it all.

Thanks for the help!

 

As it turns out, the battery is an issue independent of the starting issue. Once conditions warmed up again, the car had trouble starting again.

 

My daughter has a 2007 Mazda 6. Exact same problem. Have been to the dealer numerous times. They replaced fuel pump and computer. It also starts up fine most of the time. But finally noticed the no-start when hot. Have not checked the temp on the dash-good idea. Has been towed to the deaaler several times but always starts fine when it gets there. I don't understand why they cannot diagnose the problem. They have never found any codes either. Did you ever find out what the problem was? She is considering selling this car which she loves and has 39,000 miles which has never had any other issues, but it is unnerving to have a car that is unpredictable! Thanks!

 

I had a load test done on the battery at a Batteries Plus which indicated that I need a new battery. I bought one and the problem disappeared for a year but has since returned.

For one, I think there might be a faulty temperature sensor somewhere as my dashboard thermometer is pretty wonky. However, I suspect that it is actually my driving patterns that is killing the battery and then the heat somehow keeps the battery from producing enough juice to start.

Driving pattern consists of a lot of short trips of no more than a mile during the week. If I'm starting my car a lot and not giving it a chance to recharge the battery, the battery will wear out rather fast. I'm not sure why the car getting hot in the sun triggers the no-start behavior but I've always been able to leave my fans running for 5 mins or so, maybe put the car in neutral and get it in the shade and pop the hood to cool it off, and then I can get it started.

Also, after long trips where the battery can recharge as much as possible (of course its ability to recharge is reduced by all the wear and tear from short trips) the car seems to be temporarily relieved of the problem as long as it doesn't get reallly hot in the sun.

my suggestion is to get a battery with a good warranty so if you have a driving pattern like mine you can get it replaced after a year. don't take it to the dealer... they can't diagnose intermittent faults easily, especially if it doesn't leave a code in the computer.

 

Try this. Our gasoline today is so bad. The oil companies have a summer gas and a winter gas. Try the higher octane. Be sure you get most of the old gas out. The unleaded has a lower boiling point due to the crap they add to the gas, otherwise known as filler. that should help. also Chevron has other addatives that help

 

I will add that summer 2010, after replacing the battery, my startup problems ceased until early summer 2011 when it finally got hot here again. Only happened a few times and not at all in a couple months, even though it has been hot. This may have been due to a stretch of making very short trips where the battery did not have time to charge.

I have tried fuel line cleaner in the past but no other additives or higher octane fuel. So I can't really rule out something like vapor locking or a problem with the fuel or fuel pump, although that seems unlikely. However, it would be a relatively cheap solution to test. If the car starts acting up again I might give that a shot.