# What just happened to my Mustang GT? **URL:** \ **Category:** Factual Questions\ **Created:** [January 25, 2013, 3:56pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327 "2013-01-25T15:56:21Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![FoieGrasIsEvil](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/foiegrasisevil/32/16638_2.png) [@FoieGrasIsEvil](https://boards.straightdope.com/u/FoieGrasIsEvil)\ **Post date:** [January 25, 2013, 3:56pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327/1 "2013-01-25T15:56:21Z")
This is a weird issue. I was driving my 2008 GT to work this morning and I was in the left lane doing about 65 in 5th gear. I realized that I was losing ground to the car in front of me as he’d sped up and the car behind me was gaining. So, I give the car a little throttle while still in 5th gear to keep pace with the traffic in front of me. Right after applying the throttle, the car lurched and then the little yellow wrench light (I guess that’s the check engine light in a Mustang? Never seen it on before.) illuminated. For the rest of my commute the car was driving funky. The engine seemed off, reluctant to rev. When I got off the interstate and to a stop at a light I revved the car in neutral and it definitely didn’t feel or sound right. I babied it the rest of the way to work. I shut the car off, waited a few minutes, and started it again. Now the wrench light is no longer on and the car sounds perfectly fine. I rev it hard. Sounds completely normal (badass!). I just drove the thing (now in the snow…worst…snow…car…EVER!) to get something to eat and other than being extremely squirrely in the snow, the car seems totally fine. The only thing I can think of is that I went from 93 octane fuel, which is what I normally put in it even though the manual calls for 87, to regular unleaded in the last two fillups when gas prices spiked upward again. Maybe I got some bad gas or something? I find it hard to believe that gas would be the issue though, but I suppose anything is possible. The car doesn’t even have 40k miles on it yet! Any ideas from our resident gear heads? ---
**Author:** ![I\_Like\_Pie](https://avatars.discourse-cdn.com/v4/letter/i/9f8e36/32.png) [@I\_Like\_Pie](https://boards.straightdope.com/u/I_Like_Pie)\ **Post date:** [January 25, 2013, 4:02pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327/2 "2013-01-25T16:02:24Z")
Why would you be driving your Mustang in the snow? You should really consider getting a second car for inclement weather. Other than that^ I have no input. Maybe it’s the gas. ---
**Author:** ![FrankJBN](https://avatars.discourse-cdn.com/v4/letter/f/f0a364/32.png) [@FrankJBN](https://boards.straightdope.com/u/FrankJBN)\ **Post date:** [January 25, 2013, 4:09pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327/3 "2013-01-25T16:09:27Z")
One guess, one truth: Car could have been in “choke” mode, a richer fuel mix with EFI or was reset to that when you goosed it. On restart, no longer ‘confused’ as to optimum mixture. As to premium, you are definitely wasting money putting 93 octane in a car that calls for 87. Keep running 87, you will find performance will be the same as it was. ---
**Author:** ![FoieGrasIsEvil](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/foiegrasisevil/32/16638_2.png) [@FoieGrasIsEvil](https://boards.straightdope.com/u/FoieGrasIsEvil)\ **Post date:** [January 25, 2013, 4:15pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327/4 "2013-01-25T16:15:34Z")
> [@I\_Like\_Pie](#): > > Why would you be driving your Mustang in the snow? You should really consider getting a second car for inclement weather. > > Other than that^ I have no input. Maybe it’s the gas. I’m thinking of buying a 2001 Hyundai for just these kinds of days. > [@FrankJBN](#): > > One guess, one truth: > > Car could have been in “choke” mode, a richer fuel mix with EFI or was reset to that when you goosed it. On restart, no longer ‘confused’ as to optimum mixture. > > As to premium, you are definitely wasting money putting 93 octane in a car that calls for 87. Keep running 87, you will find performance will be the same as it was. Do later model cars have a choke function? I guess I’ve never heard of it. ---
**Author:** ![Kyrie\_Eleison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kyrie_eleison/32/7682_2.png) [@Kyrie\_Eleison](https://boards.straightdope.com/u/Kyrie_Eleison)\ **Post date:** [January 25, 2013, 4:18pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327/5 "2013-01-25T16:18:57Z")
[Limp mode](http://www.ehow.com/info_12199368_mean-car-goes-limp-mode.html). ---
**Author:** ![FoieGrasIsEvil](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/foiegrasisevil/32/16638_2.png) [@FoieGrasIsEvil](https://boards.straightdope.com/u/FoieGrasIsEvil)\ **Post date:** [January 25, 2013, 4:22pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327/6 "2013-01-25T16:22:57Z")
> [@Kyrie\_Eleison](#): > > [Limp mode](http://www.ehow.com/info_12199368_mean-car-goes-limp-mode.html). Interesting. Unfortunately I do not have the ducats right now to pay for a system diagnostic. I wonder if the guys at Autozone can get an accurate read on what the fault was with one of their code readers, which I think they will do for free. ---
**Author:** ![Chefguy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chefguy/32/138_2.png) [@Chefguy](https://boards.straightdope.com/u/Chefguy)\ **Post date:** [January 25, 2013, 4:23pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327/7 "2013-01-25T16:23:43Z")
> [@FrankJBN](#): > > One guess, one truth: > > Car could have been in “choke” mode, a richer fuel mix with EFI or was reset to that when you goosed it. On restart, no longer ‘confused’ as to optimum mixture. > > As to premium, you are definitely wasting money putting 93 octane in a car that calls for 87. Keep running 87, you will find performance will be the same as it was. Absolutely. There’s a reason why they recommend a particular fuel. You’re not doing your car or your wallet any favors. ---
**Author:** ![FoieGrasIsEvil](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/foiegrasisevil/32/16638_2.png) [@FoieGrasIsEvil](https://boards.straightdope.com/u/FoieGrasIsEvil)\ **Post date:** [January 25, 2013, 4:28pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327/8 "2013-01-25T16:28:14Z")
> [@Chefguy](#): > > Absolutely. There’s a reason why they recommend a particular fuel. You’re not doing your car or your wallet any favors. It doesn’t hurt the car to run higher octane…it’s a muscle car, after all. It’s probably a waste of my money and it’s probably all in my head but the car seems to run smoother with premium fuel. ---
**Author:** ![steronz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/steronz/32/11765_2.png) [@steronz](https://boards.straightdope.com/u/steronz)\ **Post date:** [January 25, 2013, 4:44pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327/9 "2013-01-25T16:44:15Z")
Did it sound like it was running rough? One of your coil packs may be going bad. My guess is that this is going to happen again in the next couple of weeks, and then get more frequent until you fix whatever’s broke. I don’t think the gas has anything to do with it. ---
**Author:** ![GreasyJack](https://avatars.discourse-cdn.com/v4/letter/g/df705f/32.png) [@GreasyJack](https://boards.straightdope.com/u/GreasyJack)\ **Post date:** [January 25, 2013, 4:45pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327/10 "2013-01-25T16:45:17Z")
If the check engine light came on, there will be a code stored in the computer. You should be able to retrieve it at an auto parts store or friend with a code scanner. You mentioned snow… was it super slushy or otherwise wet when it happened? I don’t know if this car has spark plug wires or is coil-on-plug, but the description sounds like a wet ignition system on an older car. ---
**Author:** ![GreasyJack](https://avatars.discourse-cdn.com/v4/letter/g/df705f/32.png) [@GreasyJack](https://boards.straightdope.com/u/GreasyJack)\ **Post date:** [January 25, 2013, 4:47pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327/11 "2013-01-25T16:47:41Z")
> [@FoieGrasIsEvil](#): > > Interesting. Unfortunately I do not have the ducats right now to pay for a system diagnostic. I wonder if the guys at Autozone can get an accurate read on what the fault was with one of their code readers, which I think they will do for free. Oh, sorry missed this before. One thing to add is that if you have a smartphone there’s very cool and quite cheap OBDII to bluetooth adapters you can get that turn your phone into a code reader/engine scanner. ---
**Author:** ![FoieGrasIsEvil](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/foiegrasisevil/32/16638_2.png) [@FoieGrasIsEvil](https://boards.straightdope.com/u/FoieGrasIsEvil)\ **Post date:** [January 25, 2013, 4:52pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327/12 "2013-01-25T16:52:46Z")
> [@GreasyJack](#): > > If the check engine light came on, there will be a code stored in the computer. You should be able to retrieve it at an auto parts store or friend with a code scanner. > > You mentioned snow… was it super slushy or otherwise wet when it happened? I don’t know if this car has spark plug wires or is coil-on-plug, but the description sounds like a wet ignition system on an older car. It didn’t snow until later, and the car is a 2008. I assume the little yellow “wrench” light is the check engine light on this car. I’ve never seen it come on before, and every other car I’ve owned either had a little picture of an engine or a little box with “check engine” or “maint required” messages on them. ---
**Author:** ![steronz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/steronz/32/11765_2.png) [@steronz](https://boards.straightdope.com/u/steronz)\ **Post date:** [January 25, 2013, 4:58pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327/13 "2013-01-25T16:58:04Z")
On cars I’ve owned, Check Engine and Maint Req’d are two different indicators; the later usually either tied to a set mileage or to an oil-life algorithm, to indicate that the car needs an oil change or some other regularly schedule maintenance. The wrench means something’s broke, and the code should still be in the computer even though the light is off. Also, if the wrench is ever flashing, that means stop driving ASAP. I think they got rid of the little engine-looking light because people don’t know what an engine looks like. Also, the “engine” usually had a fan mounted to the crankshaft and a circular air cleaner on top, both of which are relics of the past. ---
**Author:** ![Edward\_The\_Head](https://avatars.discourse-cdn.com/v4/letter/e/ce73a5/32.png) [@Edward\_The\_Head](https://boards.straightdope.com/u/Edward_The_Head)\ **Post date:** [January 25, 2013, 5:05pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327/14 "2013-01-25T17:05:55Z")
> [@FoieGrasIsEvil](#): > > It didn’t snow until later, and the car is a 2008. I assume the little yellow “wrench” light is the check engine light on this car. I’ve never seen it come on before, and every other car I’ve owned either had a little picture of an engine or a little box with “check engine” or “maint required” messages on them. I don’t have a more modern Mustang but I do have an 07 Ford Escape and owned lots of other Fords. On all of the Fords I’ve seen the engine light looks more like a box engine, says Check Engine in it and is red. Could it be the low pressure sensor for the tires? ---
**Author:** ![FoieGrasIsEvil](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/foiegrasisevil/32/16638_2.png) [@FoieGrasIsEvil](https://boards.straightdope.com/u/FoieGrasIsEvil)\ **Post date:** [January 25, 2013, 5:06pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327/15 "2013-01-25T17:06:14Z")
> [@steronz](#): > > Did it sound like it was running rough? One of your coil packs may be going bad. > > My guess is that this is going to happen again in the next couple of weeks, and then get more frequent until you fix whatever’s broke. I don’t think the gas has anything to do with it. Yes, it did run rough for the last half of my commute. Is it common for a COP to go bad so early in a car’s life (mileage speaking)? I don’t think it’s the gas either. Is it possible for a car to have a computer glitch that can adversely affect performance? > [@steronz](#): > > On cars I’ve owned, Check Engine and Maint Req’d are two different indicators; the later usually either tied to a set mileage or to an oil-life algorithm, to indicate that the car needs an oil change or some other regularly schedule maintenance. The wrench means something’s broke, and the code should still be in the computer even though the light is off. Also, if the wrench is ever flashing, that means stop driving ASAP. > > I think they got rid of the little engine-looking light because people don’t know what an engine looks like. Also, the “engine” usually had a fan mounted to the crankshaft and a circular air cleaner on top, both of which are relics of the past. You are right about the “maint req’d” light. That’s a “get your oil changed” reminder light. ---
**Author:** ![FoieGrasIsEvil](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/foiegrasisevil/32/16638_2.png) [@FoieGrasIsEvil](https://boards.straightdope.com/u/FoieGrasIsEvil)\ **Post date:** [January 25, 2013, 5:07pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327/16 "2013-01-25T17:07:16Z")
> [@Edward\_The\_Head](#): > > I don’t have a more modern Mustang but I do have an 07 Ford Escape and owned lots of other Fords. On all of the Fords I’ve seen the engine light looks more like a box engine, says Check Engine in it and is red. Could it be the low pressure sensor for the tires? No, that’s actually happened before and that display is in the instrument cluster readout. ---
**Author:** ![jasg](https://avatars.discourse-cdn.com/v4/letter/j/f0a364/32.png) [@jasg](https://boards.straightdope.com/u/jasg)\ **Post date:** [January 25, 2013, 5:19pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327/17 "2013-01-25T17:19:32Z")
> [@FoieGrasIsEvil](#): > > It didn’t snow until later, and the car is a 2008. I assume the little yellow “wrench” light is the check engine light on this car. I’ve never seen it come on before, and every other car I’ve owned either had a little picture of an engine or a little box with “check engine” or “maint required” messages on them. google says the ‘wrench’ is maintenance required ---
**Author:** ![FordTaurusSHO94](https://avatars.discourse-cdn.com/v4/letter/f/f07891/32.png) [@FordTaurusSHO94](https://boards.straightdope.com/u/FordTaurusSHO94)\ **Post date:** [January 25, 2013, 5:31pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327/18 "2013-01-25T17:31:54Z")
A bad COP feels like a slight stumble. Is it possible a vacuum hose is loose or has a hole in it? That will make it act funky. Also, until you tune the car for 93 octane, it will run best and make the most power on 87 octane fuel. The lowest octane you can run without pinging is the best fuel for your engine. ---
**Author:** ![Spud](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/spud/32/347_2.png) [@Spud](https://boards.straightdope.com/u/Spud)\ **Post date:** [January 25, 2013, 5:35pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327/19 "2013-01-25T17:35:36Z")
> [@FoieGrasIsEvil](#): > > It didn’t snow until later, and the car is a 2008. I assume the little yellow “wrench” light is the check engine light on this car. I’ve never seen it come on before, and every other car I’ve owned either had a little picture of an engine or a little box with “check engine” or “maint required” messages on them. The wrench is actually the Electric Throttle Control (Limp Mode) light. Per the owners manual for my 06 GT it says to “report this fault to the dealer at your earliest convenience.” Check Engine (actually Service Engine Soon) is a little engine. ---
**Author:** ![Kenm](https://avatars.discourse-cdn.com/v4/letter/k/bc79bd/32.png) [@Kenm](https://boards.straightdope.com/u/Kenm)\ **Post date:** [January 25, 2013, 5:42pm UTC](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327/20 "2013-01-25T17:42:41Z")
Turn the ignition on but don’t start the engine. With GM, all the warning icons illuminate, at least for a few seconds, so the driver knows whether they all work. Ford likely’s the same. [Next page](https://boards.straightdope.com/t/what-just-happened-to-my-mustang-gt/648327.md?page=2)