Hello again and thanks in advance for any advice.

My 2004 MT (~42k miles) is having engine death as I am coming to a stop. The car is pretty much stock except for a K&N air filter. Regular maintenance has been done and it got a new engine at ~30k miles from Mazda.

I replaced the battery yesterday to a Duralast Gold (640 cold cranking Amps (800 cranking Amps), so we should be well above the power needs. Hooray for summer heat.

The car starts up fine in no more than 2 seconds. After a few minutes of driving, the battery indicator on the dash will either flash or stay lit when I am coming to a stop, always when I am very close to actually stopping. If it just flashes, the idle is a bit rough but I'm ok and can continue to drive. If the led stays lit, all four lights in that column light up, including the CEL and the car is dead. I can then start the car normally. Lather, rinse, repeat. During this driving around I have the A/C and radio shut off to minimize power draw.

I limped over to where I bought the battery and they checked the power system. The whole system, including the alternator, checks out. The thing is that the CEL is not on and there are no codes in the computer.

Any ideas on where to start? I don't see any blown fuses and everything under the hood looks normal.

EDIT: I did search, but everything I saw was related to the CEL actually being lit.

 

You mentioned the K&N - is it the panel type or the whole 'intake' model?

S

 

Its just the panel type to drop-in replace the factory air filter. Nothing fancy.

 

sounds like a loose ground wire to me, since the alternator is generating juice and the battery is fresh yet your having electrical issues. Not hard to accidentally leave a ground loose in a modern car with a bazzilion grounds under the hood alone. Could also be a faulty cable or other connection. How does the car act with the head lights on?

 

Thanks for the input. Shouldn't the ground wires either be part of the battery cables or fairly obvious around the battery holder? I'll double check around there that I didn't nudge a cable off.

I did a reset of the firmware and it seems to be better. It is still idling rough, but that could be from the computer relearning. I drove around at lunch for a good 10 minutes with many stops without a stall/death. We'll see how it goes on the way home. Surely the firmware would have been reset by the battery switch. Maybe it did a bad reset to defaults or something like that.

I'll see how it does with headlights on after work.

 

Actually could be a compression issue as well, both of my previous engines started stalling before dieing completely and right when it would die the alternator light would flash. i never got a CEL before either engine lost compression.

If you can borrow a Scangauge or something that can monitor voltage while driving to rule out and electrical problem. Does this only happen when the engine is hot?

 

At this point the firmware/software reset I did yesterday morning seems to have fixed it. The car hasn't died with or without A/C, radio, headlights, etc since then. My only guess would be that while hooking the new battery up I disconnected it while the computer was resetting back to defaults and the controls got all messed up. Who knows.

I sincerely hope its not a compression issue as the new engine doesn't even have 13k miles on it. As for relating it to heat, its been in the mid- to upper-90s the last few days so its always hot. Regarind the engine warmup, it was at all levels.

A somewhat related question since I'm a bit of an electrical noob. Would the material of the bolt holding one of the battery leads onto the battery post affect anything? I had a bolt snap during the installation and had to use a random 10mm bold to finish up the job. Theres no arcing or anything like that, but could it mess with the ground?

 

The bolt shouldnt matter as long as it fits, fits tight, and makes the connection tight.

 

Yea remove and clean battery connections. Sometimes grease or whatever can get on there. If that does not work take
the battery back. When I used to work parts counter we had some bad batteries come back that where new.

 

Sometimes the alt check out and is actually bad.. Try removing the negative cable and see if it stays on or off...

 

Take the car to your local auto parts and have them check your altenator!, it should be free and fast; it is for me at advanced auto parts.