Car repair mystery

malibu
chevrolet

#1

So I’ll start from the beginning. This has been a long winded problem but I still haven’t found the solution. It started a couple months ago when I was driving home from work. I made it to the stop sign just outside of my work building and my car just stopped. The engine quit and wouldn’t restart, followed quickly by the battery dying. So I pushed the car back into the parking space and took the battery in to be tested/replaced the next day, hoping that would be the end of it. Nope. Not even close. After replacing the battery, the car ran fine for about a day or two. No problems at all. Then, once again, the car died on the way home from work but this time it was a little different. The power didn’t die, but the engine wouldn’t turn over. It would try, but would never quite make it. So I had it towed to my mechanic friends shop. He ran a scan on any codes going off and it turned out the MAP sensor had gone bad. So we replaced that. Again, the car ran fine for about a day and a half and the exact same thing happened. The car sputtered out, RPMs fluctuated and then died out and wouldn’t start up again, but power never failed. So we tried replacing the alternator. Same deal again. Runs fine, dies, power remains, won’t restart.
So we tried something else. The next time it died I removed the negative cable from the battery and put it back on about 10 seconds later and then the car would restart and run fine again for the rest of the day. This problem still persists. The car is a 2010, under 100000 miles (91,000), oil changed regularly and the transmission has been entirely replaced once at 72,000. Any ideas would be appreciated. My mechanic is at his wits end.


#2

You mean it wouldn’t crank? At all? I think your car’s ECU is the type that the ignition-crank position is just a command to set the car into a “crank until start” sequence. In other words, you can turn the key for just a small moment and the car continues to crank until it starts (or it stops based on error codes or a time-out) no matter if you hold the ignition into the “crank” position or not. If that is the type of ECU you have, that may be your problem right there.

This acts like a temperature related electronic failure. Drive a while, get hot, die, do “something” that takes time, car restarts and runs fine for a while. It would be great if you could duplicate this with the mechanic IN the car holding a scan tool watching to see that it isn’t something simpler. Like a crankshaft or camshaft position sensor failure. These are sensors that tend to exhibit these heat related intermittent failures.


#3

It doesn’t SEEM to be temperature related, by which I mean the failure seems to be completely random at any point during the drive. It’s happened 1 minute into a drive, it’s happened 40 minutes into a drive. It’s not terribly consistent. The temp gauge never goes above what would be normal either.


#4

Its not that the engine is overheating, just the components get warm from operation and stop working properly.

Your reply reinforces my thoughts that is may be an ECU problem. Since it can occur in as little as one minute, a ride with a mechanic with a scan tool is a good idea.

One bright point. It is very unlikely to get better, most likely to fail completely so then the mechanic can diagnose it.


#5

Remove the positive battery cable bolt and check it for corrosion.

This is a common problem with the GM side mount battery cables.

And if you find this corrosion, replace the cable assembly.

Tester


#6

Thanks for the tips. I’ll contact my mechanic and get him to do a ride along if the bolt isn’t the problem.


#7

Mr Tester has your answer. When most battery cable connections get corroded, they are able to carry the current to run the lights, radio and such, but not the heavy draw that it takes to turn the starter and engine over.
Sometimes you get lucky and they carry the heavy load until you hit a bump in the road and they lose their connection.

I’d do as tester said and clean the terminal face on the battery and both sides of the terminal on the cable. If those bolts/studs that Tester is shown holding are corroded or rusted badly…new ones can be bought at any autoparts store.

Yosemite


#8

So the car seems to be running ok, then suddenly the engine sputters and stalls. After that it won’t crank. Will it ever crank once it gets into the no-crank mode? I ask b/c you say this same thing has happened again and again. So how do you finally get it to crank and run again? Just by disconnecting the battery?

hmm … and you’ve replace the alternator and the MAP sensor? On guess, there was nothing wrong with the MAP sensor. Those rarely fail. So be sure to keep the old one. It’s probably still ok. They make for good diy’er barometers and altimeters for amateur scientists if nothing else. The code for the MAP sensor was probably caused by the electrical power problem.

I think what I’d do if I had this problem is have the work done for the battery cables as described above, then battery and charging system tested, then charge up the battery and test for phantom current drain when the engine is turned off.