AMDanBailer

Mustangs just take a long time to warm up. If it's doing it on the stock tune and the Bama tune, then it's definitely just not warm enough.

Next time you let it sit overnight, turn off the Defrosters and/or A/C, so the compressor isn't on. Let the car warm up to half or 2/3ds of operating temperature and then drive it. Getting a car to operating temperature before driving it is always recommended. When the car is cold, it's not ready to be driven hard or shift gears quickly. Letting it warm up before driving should solve your problem.

If not, check the fuel filter, fuel pump, injectors, and for any possible vacuum leaks. I would bet it's just because it's not warmed up (hence why you don't notice it when it is warm).

Wpipes

I have the exact same issues as described by BrockGrimes. Stock automatic 05' GT with 20k miles, and according to my uncle (of whom I bought it from) it was the only issue he had as well.

It will happen even after the car is warm (after driving for maybe 15 minutes), I'll stop at a light and if I try to make a slow steady acceleration it bogs like it's going to die before it lets me accelerate at all. It will occasionally die after shifting into reverse and back to drive as well.

ski

I agree with your latter statement, but respectfully disagree with the former one.

Allowing a car to warm up for extended periods before driving is not recommended for the following reasons:
- It wastes gas.
- It increases the amount of time for the engine to warm up to normal operating temperature, because it's not operating under a load. This in turn extends the amount of time the engine is fed a rich fuel ratio, which not only dilutes the protective oil coating on the cylinder walls that can increase the possibility of the walls getting scored by the piston rings, but it also contaminates the oil due to extra gas and water vapor seeping by the piston rings. Plus, it increases emissions.
- It extends the amount of time for the catalytic converter(s) to heat up to normal operating temperature, which also causes increased emissions and possible premature converter failure.
- It causes larger amounts of water vapor in the exhaust gas to condense and accumulate inside the exhaust system causing metal components to corrode quicker.

AMChrisRose

Ski,

GT's from 05-09 (earlier 05-06 specifically) have had known issues in the past with VCT being noisy and uncontrollable until the car warms up and oil temperature is high enough. This obviously has a direct impact on power, and is why Ford had a redesigned cam phaser and TSB. This is also why you need to run 5w20.

When the car starts, the air/fuel ratio is going to be controlled by the front oxygen sensors. They'll be warm much more quickly than the engine, and keep the air/fuel ratio at 14.64, or stoichiometric - which is fine, and won't cause any issues with catalytic converters or cylinder walls.

Actually, it's quite the opposite. It's when you drive (depending on your driving habits / throttle position / engine load) that the car will dump fuel by using a cold base fuel table which commands a rich air/fuel ratio until your car hits operating temperature. Even at that, though - part throttle will still maintain stoichiometric air/fuel ratio.

Sitting and letting your car warm up is a pretty good idea.

Chris

ski

I originally thought the ECU remained in OL mode after a cold start by ignoring the O2 sensor's signal until the coolant temperature sensor signal indicated the coolant has risen to a specified temp. That's apparently no longer the case in order to more quickly minimize emissions.

However, it appears internal viscous forces will cause the engine to stall if it went into CL mode only a short time after start up, and long before the oil had a chance to warm up. To prevent that from happening, my observations indicate that the ECU runs the engine at higher than normal idle rpm's for a much longer period if my car is not immediately driven after start up. And that just wastes ga$, and spews more emissions.

Another observation is my GT's engine does not reach a partially warmed up state in cold weather(30 F +/-) until it's traveled for at least 5 miles or more(approx. 10-15 min. in my area) after a cold start. Test results show it takes twice as long to do the same when it sits and idles in my driveway. More wasted ga$, and more emissions.

And as I mentioned in my previous post, the cats do not operate at optimum efficiency until they are at normal operating temperature, which takes a much longer time if a car idles at a standstill. And that also increases emissions.

IMHO, I still believe it's best to drive a vehicle immediately after it's been started, and to drive conservatively until the engine is at least partially warmed up to maximize mpg and minimize emissions.

BrockGrimes

My issue drives me crazy due to the fact it's intermitent and seems to happen around 1500-2000rpm. It's no the fuel pump TSB issue that's after hopping of the interstate. This is a first thing in the morning startup, it's the slow pull off from a dead stop is when I get it. One of the ford mech's said those fuel pump modules arestupid sensitive to voltage and that could be the issue. But I would expect it to happen all the time not just 1-3rd gear slow going in the morning. It also doesn't matter in the ac, heat, fan, etc are on or off. I've combed more threads than I can count on this subject but no one has a solution. I hate going to the stealership as more of the f-tards seem to just guess rather than really hunt for the problem.

I even installed a new tps and cleaned out the intake from the filter to the throttlebody with maf cleaner. BTW stock air cleaner setup.

Wpipes

I'm right there with ya Grimes. I'm hoping when I purchase my new CAI/Tune it will help (if the issue has something to do with the air filter or intake). The TPS replacement was my next step so it bums me out that it didn't work for you as that kills my hopes for a solution there a bit.

The only other thing I can think of is a problem with the fuel line?

BrockGrimes

Mine had it before and after the tunes so I'm leaning toward fuel related issue.
Maybe that fuel pump controller module wtf it's called.

AMChrisRose

In 2010-down Mustangs, the car does start in open loop, but goes back into closed loop very quickly, even from a pretty cold start. There, you're absolutely correct. It will, if you want to nitpick, consume fuel and raise emissions by idling higher, etc. for a few moments. But that's never ever going to be noticeable to most people.

There are a few temperature points - one, the front O2 sensors. They need to heat up after turning the car on to allow the car to go back to closed loop. This could take... 30 seconds, lets say. Then, there's the temperature you have to get to before you will use most "standard" tables in the tune and not "cold" tables. This could be set to anything, but typically ~150 degrees. I guess what I'm getting at is that you only have about 30 seconds of the car being "a fuel hog" before it's fine. Yet, you could have 2-3 minutes of the car being a "fuel hog" when you actually start driving. It makes sense to stay put.

When you're talking about how much more gas you use or emissions you put out, we're talking about idling for like a few minutes or so, here. Just to get it to a reasonable temperature so that the front o2 sensors are warm enough to be as accurate as possible, the engine oil temp is as high as you can get it in that few minutes, so that VCT doesn't go nuts, etc. The car will idle higher, and the idle will come down as temperature rises. Even if you got into the car and started it and hit the throttle immediately, most people have driveways, stop signs, traffic lights, etc. before they get to a main road. They're going to spend plenty of time at idle during that trip. And it's still going to idle higher and you're still going to be at higher RPMs for the majority of the time, thus making more emissions.

At this point, we'd be debating about things that people would see in tests and datalogs in controlled environments, etc. If we circle back to the everyday Mustang owner, starting their car for a few moments will never make a noticeable difference in gas mileage or raise emissions enough to be a concern. They'll do more harm to the environment with one 10 minute blast in an off-road x-pipe than they will with 5 winters of starting a car a few moments before driving it.

Now 2011+ Mustangs always operate in "closed loop" because they have lambda sensors, but we'll ditch that from the conversation.

There's the lab and the engineering board, and then there's the actual environment. In the real world, these cars have to be built to withstand the guy who turns the car on and goes. However, it's in many ways better to let most applications reach operating temperature before driving the car.

BrockGrimes

Anyone got suggestions on this hesitation thing?
Believe me if I figure it out everyone will know.

I've got the texas mile coming up in march and I'm worried how a top speed run will be
if this turns out to be bigger than just a hesitation.