# New car manual craziness **URL:** \ **Category:** Factual Questions\ **Created:** [May 10, 2001, 8:12am UTC](https://boards.straightdope.com/t/new-car-manual-craziness/64973 "2001-05-10T08:12:53Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![sethdallob](https://avatars.discourse-cdn.com/v4/letter/s/e36b37/32.png) [@sethdallob](https://boards.straightdope.com/u/sethdallob)\ **Post date:** [May 10, 2001, 8:12am UTC](https://boards.straightdope.com/t/new-car-manual-craziness/64973/1 "2001-05-10T08:12:53Z")
So I just bought a new entry-luxury car (woohoo!), and I’m reading through the manual… Under “Starting the Engine”: “In the summer, when restarting the engine within 30 minutes after it has been stopped, keep the accelerator pedal fully depressed while starting.” What the hell? What does that do aside from flood the engine? ---
**Author:** ![Rue\_DeDay](https://avatars.discourse-cdn.com/v4/letter/r/41988e/32.png) [@Rue\_DeDay](https://boards.straightdope.com/u/Rue_DeDay)\ **Post date:** [May 10, 2001, 11:23am UTC](https://boards.straightdope.com/t/new-car-manual-craziness/64973/2 "2001-05-10T11:23:37Z")
It doesn’t flood the engine. Depending on which entry-luxury car you have, the computer that runs the whole gas/air mixture show just opens up the air intake (since there’s fuel vapor already in the cylinder) and lets the car start. ---
**Author:** ![sethdallob](https://avatars.discourse-cdn.com/v4/letter/s/e36b37/32.png) [@sethdallob](https://boards.straightdope.com/u/sethdallob)\ **Post date:** [May 10, 2001, 3:29pm UTC](https://boards.straightdope.com/t/new-car-manual-craziness/64973/3 "2001-05-10T15:29:56Z")
But why do I only have to do it under the conditions above? I also don’t understand why I won’t redline myself as soon as I crank the engine (it’s an Infiniti I30). ---
**Author:** ![Joe\_Cool](https://avatars.discourse-cdn.com/v4/letter/j/ecb155/32.png) [@Joe\_Cool](https://boards.straightdope.com/u/Joe_Cool)\ **Post date:** [May 10, 2001, 4:20pm UTC](https://boards.straightdope.com/t/new-car-manual-craziness/64973/4 "2001-05-10T16:20:56Z")
> [@](#): > > \*Originally posted by sethdallob \* > **But why do I only have to do it under the conditions above?** Under those circumstances, starting the car can be harder due to vapor lock. Those steps are to avoid it. > [@](#): > > \*\*I also don’t understand why I won’t redline myself as soon as I crank the engine (it’s an Infiniti I30). \*\* Because you (hopefully) have the sense to let go of the pedal after it is started, and before you get to redline. ---
**Author:** ![Rue\_DeDay](https://avatars.discourse-cdn.com/v4/letter/r/41988e/32.png) [@Rue\_DeDay](https://boards.straightdope.com/u/Rue_DeDay)\ **Post date:** [May 10, 2001, 4:57pm UTC](https://boards.straightdope.com/t/new-car-manual-craziness/64973/5 "2001-05-10T16:57:19Z")
I couldn’t find the cite I was looking for, but I found [this](http://www.pelicanparts.com/914/914QA/914Q_engine_starting_step_on_gas.htm). It’s for a Porsche, but the important part… > [@](#): > > If the car is hot and won’t start, you press the pedal all the way down without pumping it until it starts. Giving the car gas doesn’t necessarily give the cylinders more gas, it just allows more air to flow through the throttle body. was pretty much what I was thinking of. If you _pump_ the gas, you’ll flood the sucker. And when I previewed, I saw Joe\_Cool’s post…yeah, what he said. Openning the throttle body breaks the vapor lock. When it’s cool, the vapor condenses back to liquid gas and it’s not a problem. Sometimes the redline problem is circumvented by the engine computer, it won’t _let_ you redline on startup. I wouldn’t test it though. I’d just take my foot off the gas when the car starts. ---
**Author:** ![cornflakes](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@cornflakes](https://boards.straightdope.com/u/cornflakes)\ **Post date:** [May 10, 2001, 8:17pm UTC](https://boards.straightdope.com/t/new-car-manual-craziness/64973/6 "2001-05-10T20:17:31Z")
You can’t flood a modern fuel injected car; the injectors don’t open until the spark plugs are firing. They probably want you to open the throttle because the engine doesn’t know how it is running until it begins to run. To make sense of that last statement, the engine control module (or ECM) adjusts the air/fuel ratio based on the temperature of the coolant in the engine (along with a lot of other things.) But the coolant temperature is really supposed to represent the temperature inside the cylinders. The insides of the cylinders cool off faster than the coolant does, so the ECM probably adds a little more fuel than is necessary when when you start the engine warm. Opening the throttle allows the engine to draw in more air, evening things up. Once the engine is running, the ECM can make adjustments based on how the engine is running. Personally, I’ve never had a problem starting an injected car with my foot off the throttle, whether the engine is hot, warm or cold. ---
**Author:** ![Rue\_DeDay](https://avatars.discourse-cdn.com/v4/letter/r/41988e/32.png) [@Rue\_DeDay](https://boards.straightdope.com/u/Rue_DeDay)\ **Post date:** [May 11, 2001, 11:43am UTC](https://boards.straightdope.com/t/new-car-manual-craziness/64973/7 "2001-05-11T11:43:55Z")
> [@](#): > > \*Originally posted by cornflakes \* > **You can’t flood a modern fuel injected car; the injectors don’t open until the spark plugs are firing.** If by “flood”, you mean “fill the carburetor with gas, so the engine can’t turn over”: then no, you can’t flood a modern fuel injected car. No carburetor to fill with gas. If by “flood”, you mean “pump too much gas into the cylinder, so it’s hard to start”: yeah, you can do that. The fuel injectors are not open yet, but there’s a wave of gas right behind them. When the plugs fire and the injectors open, too much gas squirts through (A very little extra gas from the very little extra pressure. We’re talking gas vapor in the cylinders, just a little extra and it wouldn’t combust so well) and it’ll take a couple of “cranks” till the engine “catches” well. And a few seconds till the engine gets enverything back in working order and runs smoothly again. It’s not the classic “flood” where your carb’ sloshes around with liquid gasoline and you’re stuck till the stuff evaporates, but you’re still “flooded” in that too much gas is keeping your car from running properly. When was the last time you “dialed” a phone with an actual dial? My assumption is: a 1996 Honda Civic DX Hatchback (Silver) qualifies as a “modern fuel injected car”. Been there, done that, bought the t-shirt. sethdallob, the important part of the whole “keep the accelerator pedal fully depressed while starting” deally is to open up the airflow. When your car is still hot, the engine conditions don’t match the baseline the computer uses to start your car. More air in the fuel mix lets the car start easier. Call it “vapor lock”, “flooding”, “stupid ECM”, whatever. Depressing the throttle all the way helps to start your car when it’s hot and won’t start right by giving the engine more air. It might not do anything really, it could be something for you to do while you’re trying to get your car started so you feel like your really doing something to help the process along. It could be Detroit Voodoo. Hopefully you’ll never have to find out because your car will always start the first try. Just don’t pump the gas. ---
**Author:** ![cornflakes](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@cornflakes](https://boards.straightdope.com/u/cornflakes)\ **Post date:** [May 11, 2001, 3:51pm UTC](https://boards.straightdope.com/t/new-car-manual-craziness/64973/8 "2001-05-11T15:51:19Z")
> [@](#): > > If by “flood”, you mean “fill the carburetor with gas, so the engine can’t turn over”: then no, you can’t flood a modern fuel injected car. No carburetor to fill with gas. Are you referring to a hydraulic lock where the cylinders fill with gas? I learned that a flooded engine is one that will not start due to a too rich condition, not one that is slow to start. You’re right, it is a matter of degree, but I have never had an injected car flood out and not start. I think my post implied that the open throttle might help the car start faster. > [@](#): > > If by “flood”, you mean “pump too much gas into the cylinder, so it’s hard to start”: yeah, you can do that. The fuel injectors are not open yet, but there’s a wave of gas right behind them. Why wouldn’t any pressure waves in the fuel lines pass through the bypass regulator and back into the tank? Browsing around, I did find a reference to [“the clear flood mode”](http://www.chevythunder.com/fuel%20injection%20troubleshooting%20pg%20a.htm) (page down twice.) > [@](#): > > When the ecm sees the engine being cranked, and the throttle angle is more than 80%, the ecm will shut off the injectors, or lean the mixture out to approximately 20:1 to help start the vehicle. This further leans out the mixture (_which I think we all agree is a good thing_.) Pumping the throttle while cranking the engine would limit this mode of operation. Pumping the accelerator with the engine off of course makes no more difference than pressing ctrl-alt-del on your PC with the cord unplugged. The system is powered off, and doesn’t read the input. > [@](#): > > My assumption is: a 1996 Honda Civic DX Hatchback (Silver) qualifies as a “modern fuel injected car”. I added the phrase to rule out odd stuff like Hillborn injection, where fuel flow is directly controlled by the accelerator. > [@](#): > > …When was the last time you “dialed” a phone with an actual dial?.. > > …Been there, done that, bought the t-shirt… **…**