The Truth About Cars » engine computer http://www.thetruthaboutcars.com The Truth About Cars is dedicated to providing candid, unbiased automobile reviews and the latest in auto industry news. Sat, 02 May 2015 17:49:40 +0000 en-US hourly 1 http://wordpress.org/?v=4.0.1 The Truth About Cars is dedicated to providing candid, unbiased automobile reviews and the latest in auto industry news. The Truth About Cars no The Truth About Cars editors@ttac.com editors@ttac.com (The Truth About Cars) 2006-2009 The Truth About Cars The Truth About Cars is dedicated to providing candid, unbiased automobile reviews and the latest in auto industry news. The Truth About Cars » engine computer http://www.thetruthaboutcars.com/wp-content/themes/ttac-theme/images/logo.gif http://www.thetruthaboutcars.com Piston Slap: The Low Oil Pressure Safety Net? http://www.thetruthaboutcars.com/2015/04/piston-slap-low-oil-pressure-safety-net/ http://www.thetruthaboutcars.com/2015/04/piston-slap-low-oil-pressure-safety-net/#comments Wed, 29 Apr 2015 13:00:24 +0000 http://www.thetruthaboutcars.com/?p=1054825   TTAC Commentator r129 writes: Hello Sajeev, My 2012 Impala with 20,000 miles was due for an oil change, something that I was too lazy to do myself, especially in winter weather. I know, I should know better. I went to a reputable quick oil change establishment (if such a thing exists) that uses name-brand dexos1 […]

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2009-dodge-challenger-r-t-digital-oil-pressure-gauge

Not to worry? (photo courtesy: internetautoguide.com)

TTAC Commentator r129 writes:

Hello Sajeev,

My 2012 Impala with 20,000 miles was due for an oil change, something that I was too lazy to do myself, especially in winter weather. I know, I should know better. I went to a reputable quick oil change establishment (if such a thing exists) that uses name-brand dexos1 approved oil. Everything went as expected, until I drove away. Just after I pulled out of the parking lot, the “Low Oil Pressure – Turn Engine Off” warning light came on. Before I managed to safely pull over, the engine stalled out, and I coasted into a parking spot. There were no unusual noises before the car stalled. We are talking a time span of maybe 30 seconds after leaving the parking lot, and a distance of less than a block.

Damn! This is the kind of thing that happens to people on the internet, not to me!

I walked back to the place, told them what happened, and I noticed a trail of oil leading out of the garage door where I exited. They filled up a container of oil, grabbed some items, and we walked to my car. After poking around, they told me that the filter was defective (it looked like someone had punched a hole in it with a screwdriver), but I’ll never know if they just punched a hole in it to cover up some other cause. They replaced the filter, filled up the engine with oil, and tried to start the car a couple of times. Nothing. It didn’t even try to turn over, just a “click” sound. We walked back to the shop, and at this point, I’m thinking that the oil change place is going to be paying to replace my engine. I waited while they called the store manager. I was assured that they would tow my car, any repairs would be covered in full, even if I needed a new engine, and they would provide a rental car.

But wait! The manager suggested trying one more thing. Disconnect the battery, wait 5 minutes, and try starting the car again. The rationale was that maybe the engine had shut itself down into some sort of “safe mode,” and needed to be “reset.” I was skeptical, but we walked back to the car, tried it, and it cranked up. The engine sounded normal, and I drove it back to the shop. They drained the oil, refilled it to the proper specs, checked the OBD codes, and proclaimed that the car was “okay.” I was given a copy of an incident report that was filled out detailing what happened, credited for the cost of the oil change, and sent on my way. I argued that the car should be checked out by a third party to be sure that there is no damage. The manager told me that if there was anything wrong with the car, they would be responsible for the repairs, but if nothing was wrong, they probably wouldn’t pick up the cost of having it checked out. At this point, I just wanted to get out of there after nearly 2 hours, so I left. Everything seemed normal on the drive home, but after scouring the internet for advice, I think I’m supposed to be scared.

Is there any type of safety net that takes effect to prevent serious damage to the engine in the case of a sudden loss of oil? I don’t know enough about it, and Google is not giving me any good answers. If not, why did the engine start up the second time? How worried should I be? Most importantly, should I have the car checked out, and if so, what should be checked? Any advice is appreciated.

Sajeev answers:

Engine computers are a beautiful thing: they “listen to sensors” and are programmed to make decisions based upon sensor’s inputs. Even small engines do this cool trick.

That said, you should’ve insisted on a tow back to their shop: disconnecting the battery to clear the system defeats this safety measure, which could cause more engine wear, if not engine damage. But it sounds like you are fine, just don’t do that again. 

Your Impala is one of the many modern vehicles that turns off the engine when the computer reads troubling information from the oil pressure sensor. And it’s a sensor (detailed information), not a switch (good/bad pressure) like the bad old days of idiot lights. So the computer can notice a significant drop in oil pressure in seconds, cut power to the fuel pump and save the engine (and the car, as it depreciates) to drive another day.

I’m looking for a catchy name for this “low oil pressure engine shut down” technology, but googled nothing. Rest assured, you lost some (not all) of your oil pressure and the system saved you from serious damage. Don’t worry about it. Perhaps next time personally check the oil level before leaving their shop, if that makes you feel better!

What say you, Best and Brightest?

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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Piston Slap: The Fuel Hating Tranny http://www.thetruthaboutcars.com/2013/02/piston-slap-the-fuel-hating-tranny/ http://www.thetruthaboutcars.com/2013/02/piston-slap-the-fuel-hating-tranny/#comments Wed, 20 Feb 2013 12:56:48 +0000 http://www.thetruthaboutcars.com/?p=478193 Eric writes: My question is for Sanjeev Mehta. I purchased a 2010 4 cylinder automatic Toyota Camry LE new and have been using it as my daily driver since. My commute is almost all city driving, so I noticed a quirk about the car right away. During deceleration, the transmission seems to starve the engine […]

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Eric writes:

My question is for Sanjeev Mehta. I purchased a 2010 4 cylinder automatic Toyota Camry LE new and have been using it as my daily driver since. My commute is almost all city driving, so I noticed a quirk about the car right away.

During deceleration, the transmission seems to starve the engine almost to stalling, followed by a downshift and repeated until a stop is reached. This makes for a very jerky process for people like me that like to lightly brake for longer distances before stopping. I asked the dealership about it, they told me it was normal and it will go away after ”learning” my driving habits. Two years later, it still is around. From cruising the web and Edmunds, it seems all of the Camrys with the 6 speed auto suffer from this problem. My question is, why does this happen, why on earth would Toyota put this in their cars, and why has every professional review I’ve read of the car not highlight this problem? Is there anything I can do to alleviate this persistent problem? I had the dealership apply a TSB Toyota released for this issue a year ago, but it has not helped at all.

Sanjeev answers:

Do other TTAC writers have the same common/uncommon name mix up problem too?  What say you, Jake Baruth, Stephan Lang and Derrick Kriendler? But, I know, I know…not everything is about me. So let’s do this thang.

After a bit of Googling, perhaps your dealer applied T-SB-0287-10:

“To improve the shifting performance and smoothness during acceleration, the Engine Control Module (ECM, SAE term: Powertrain Control Module/PCM) and Transaxle Control Module (TCM) calibration has been revised.”

But this link points to something more relevant, and interesting. Many (all?) electronically fuel injected vehicles cut fuel to the engine when “extended braking” in this manner.  They’ve done it since the dawn of EEC-IV fuel injection on my super-precious Ford Fox bodies, that’s for sure.  But ye olde Foxes (5.0V8, 4-speed auto) don’t bog very much at all as they slow down to idle. So what’s the problem?

When you slow down through 6 forward gears, the motor bogs down far more often than older vehicles with only 3 or 4 cogs to swap.  When you combine this EFI program with the lack of low-end torque in modern engines (relative to the low revving engines from yesteryear) and the torque converter’s stall speed (and the computer programming added to it) you have a recipe for a boggy, clumsy downshift. In these “extended braking” situations, that is.

Simply(?) put, there are computer programs designed for maximum fuel efficiency, too many downshifting gears, computer controlled spinning fans (torque converter) and a relative lack of balls in rev-happy modern engines to ensure smooth downshifting. You’re gonna have to live with it.

Or change the way you brake.  Or get a Lincoln Town Car stick shift.

 

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry.

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