Depends on the car, and the particular gas you are using.
First of all, octane rating says absolutely nothing at all about energy content or fuel quality. Octane rating is just how much you can compress the gasoline before it spontaneously combusts. You want higher octane gas? Dump some alcohol into it. Your gas mileage will go down, but your octane rating will go up. This is just one example, but it clearly shows how higher octane gasoline can make your car run worse by lowering the energy content per gallon.
The octane rating also says nothing about the burn rate of the fuel. What often happens though is that the higher octane fuels burn slower, which can make the burn in the cylinder less efficient if the engine wasn’t designed for it.
The engine in my Cadillac requires 89 octane and runs better on 91 octane, but it’s designed for the higher compression ratio. The Toyota Camry that we used to own ran on 89 octane and ran worse on 91 octane. Poking around online, it looks like your Mustang is designed to run at a lower compression ratio. If you think that it is running better on the higher octane, it’s probably one of two things. Either you are fooling yourself, or the quality and energy content of the higher octane fuel at the gas station you go to happens to be better than the energy content of the lower octane fuel that they sell. This is one of those cases where literally YMMV. At other gas stations the exact opposite may be true. Depending on how exactly they boost the octane rating, the higher octane gas can end up with either a higher or lower energy content. There’s no way of telling which one you’ve got just from the octane rating, and gas stations don’t advertise energy content.
No. Chokes are for carburetted engines; fuel injected engines don’t need them because they actively vary the fuel/air mix already. “Choke mode” just means an injector is currently at a higher fuel/air ration than normal, and presumably Frank is saying it got stuck that way.
Well that wouldn’t be good. I don’t know if one of those would be considered covered under my powertrain warranty, which I have through Ford up to 5 years, 50,000 miles and then for life through the dealer I bought the car from provided I take it to them for my routine maintenance.
Higher-octane fuel, quite simply, has more resistance to preignition. It does absolutely nothing to run higher octane gas in an engine than it’s designed for. If you’re buying quality gas, any octane rating should be equivalent in all other ways (additives, filtration, etc.) If your engine isn’t detonating under acceleration, premium fuel will in no way improve the way it runs.
The only reason to ever put different grades of gas in a car is if the engine adapts to octane, which some do. A knock sensor controls ignition advance, and if you use higher octane, it can advance further and get slightly more power (and often slightly better mileage) than when running 87 or 89. I’ve had three cars that did so and it was usually a wash between higher mileage at higher fuel cost and vice versa. Only when I was towing or hauling a full load would I go out of my way to put 89 or 91 in.
Premium/91/93 etc. is not “better” gas except in one technical way. You really are wasting your money if your Mustang doesn’t require it.
Which typically means “Eh, nothing really wrong.” A yellow light on most cars nowadays means it threw a code to the computer (typically throttle position or engine misfire) but doesn’t detect an ongoing problem. They usually clear once you shut down and restart. You can go to the dealer or Autozone, or maybe ask around if you’ve got a car-savvy friend since most of us have at least a cheap Autozone code-reader around (mine was $15). I look up the codes and clear them at least once - if it keeps recurring, then I worry and start working on it.
A red light on the warning console typically means shut down and have it towed.
2007 V6 owner here. Your baby went into Limp Home mode, which IIRC, means it cut off half of your cylinders, hence the loss of power. It indictes either TPS or throttle body problem.
Mine did it this Monday, which I attributed to the very cold day. I goosed it around a parking lot turn (having fun) and it kicked on. Turned it off and back on, stayed off. Checked and it didn’t throw a code. Everything is fine now.
BTW, I have dedicated snow tires on and 120 pounds of sand in the trunk and she goes great in the snow.
Regarding the higher octane, I know if I want to get ethenol free gas around here I can only find it at certain stations and only at the premium level. I’m not sure if it makes any kind of difference with a car but I’ve read it’s better for the lawnmower.
Most cars that have any problem with ethanol have already caught fire and burned, or had fuel system components upgraded to accommodate alcohol. It does lower your mileage a bit.
As for small engines, the big problem is that it can etch and eat through the raw aluminum of float chambers and carburetors. Most newer equipment can handle it (plating on the carb parts, and alcohol-safe tubing, I believe) but some older mowers, blowers, etc. and some on the cheaper end might still be susceptible.
My snow blower salesman simply suggested switching off the fuel flow and running the carb dry when we store it for summer, so there you go.
Well, things gave turned for the worse. After the “wrench” light came on and the car ran fine without doing anything other than turning the car off that day, more trouble today.
Upon reaching the light at the end of an offramp on my way into work this rainy morning, the car started to judder pretty bad at idle. The check engine light came on (which IS a little picture of an engine on this car). It sounds and runs horribly in the lower rpm range, although strangely it smooths out a lot above 2,000 rpm. But the idle is incredibly bad, often dipping below 500 rpm and then jumping up to 1200 or so as what I assume is the computer compensating so it doesn’t stall.
Anyway, I took it to Autozone and they read the codes for me.
They are:
Camshaft position sensor “A” lost signal to ECM
Cam sensor condition
Cylinder misfire detected-random cylinders
Crank sensor condition
Variable cam timing over retarded-bank1
Variable cam timing over retarded-bank2
So now I am obviously taking it to the dealer. My questions are: how fucked am I? The car is still under it’s 5/50 powertrain warranty…are these components likely to be covered? The service tech at Ford (where I am dropping it off this afternoon) said if those readings were accurate then they likely would be. Not definitely…likely. That worries me, as he then proceeded to tell me that he didn’t think throttle bodies were covered and things like the alternator are definitely not covered.
Also: I have to drive this thing about 30 miles (almost all interstate) to drop it off at Ford. It seems to run okay at speed. It is just really rough at low rpm’s and idle. Is it safe to drive the thing to the dealership, or should I tow it?
WAG says the culprit is “Camshaft position sensor “A” lost signal to ECM.” Your symptoms are pretty close to what my SRT-4 did when the cam sensor went bad.
ETA: IIRC, engine management stuff is covered under the mandatory 8/80 emissions warranty.
“Camshaft position sensor “A” lost signal to ECM” would be my guess as the primary cause. Either a bad sensor, bad ECU, or bad wiring between the two. I’d agree with the tech that it’s likely covered under the warranty, but it somewhat depends on what it went bad.
The cam/crank sensor conditions are caused by a mismatch between the cam and crank sensors, understandable if one of the cam sensors isn’t working. The misfire and retard warnings are a result of it running like crap due to the bad cam sensor.
I’d probably just drive it if it were my car, but I don’t think towing is out of the question. If the repair is covered under warranty, they may cover the tow as well. Or they may arrange the tow for you; it’s worth asking.
Thanks jz…that’s good to know about the warranty. I will be sure to mention that if they try to stick me with a bill for that if that is indeed what’s wrong. Now I can’t help but wonder if these two issues (the “limp mode” wrench light in my OP versus what happened today) are related or are in fact two separate issues.
FTR, the car has been sitting for several hours and I just went and started it up. Runs perfectly fine now, though the check engine light is still on. Still taking it in for service.
I have AAA so my tow is already paid for. I’m probably just going to drive it to save time though. Time is going to be kinda essential as I need to meet my girlfriend (who’s been driving my other car as she totalled hers on Christmas Eve!) at the dealership and I need to be able to pick my sons up from school. I’d rather not wait around on AAA. Sometimes they can take an hour or more to get to you, seemingly no matter where you are.
And after about 10 minutes of driving it to the dealership from work, the same issue resurfaced. The way the car is idling it felt like it was going to blow up. It was really bad. But at highway speeds, or any engine speed above about 1800rpm the car seems normal. But ye gods, that idle! The whole car shakes and sputters and shudders like it’s about to die.
As an aside, I wonder how many people are aware of the 8/80 warranty that jz mentions that’s apparently federally mandated and how many people get screwed into paying for something that should have been covered under that had they known about it or stood their ground on it?
Ford called today and said that the car was ready. They replaced the camshaft solenoid (don’t know if that includes a sensor or whatever). They said they only had to test drive it to make sure it checked out but that it was no longer throwing error codes.
I get there after work, and the guy tells me the mechanic noticed a “slight hesitation” upon acceleration and asked me if I would let him keep it overnight again. I thought to myself “slight hesitation? Maybe I will just keep it over the weekend and see how it goes and bring it back if there’s a problem” as it is in fact covered under my warranty.
So I arrange to pick up my girlfriend (whom has been borrowing my 2nd car that I am now driving with the Mustang being in the shop), drive her to the dealership so she can drive my Hyundai home and I get into the Mustang. I get about three city blocks away from the dealership, car seems okay, I stop at a red light and the car immediately starts idling all horribly again, exactly as before. It stalled out on me and I had to limp it back to the dealer so they can look at it again tomorrow. It did not however, trigger the check engine light, which I thought was weird since the symptoms are the same.
How in the world did they not notice this? Slight hesitation my ass!
