98 Grand Am GT 3.1 engine Very high idle when started. Sometimes you can shut it off and restart it and it will idle fine. Also using lots of gas. Have changed TPS, Iac, and EGR valve. No vacuum leaks can be found. Only codes thrown was a Random Multiple Misfire code. Could the Mass Airflow sensor cause this, or is it more likely a ECM problem?

The most common causes of this are a engine vacuum leak and a sticking idle speed control air bypass valve.

have the alternator checked. if the alternator is not charging the vehicle is only supplied with what power is stored in the battery. once the battery is dead there is nothing to charge it

It runs fast because the choke and or high idle are set. This is normal, after it warms up, give it a little gas and let off, it should idle down.

I would have to say the fuel/water separator filter is clogged up. The filter will remove water and crud from the gas. It looks more like a small can under the car. If the car set up with a low tank of gas, water will condensate inside and once the new fuel sloshes around it gets all this junk off the walls of the tank and that gets sucked in the filter. Try and replace that first..

Have you ever changed the fuel filter? If it's not that, and it's not a vacuum leak, it is probably your idle air control valve.

You have a cold start injector. It basically primes the fuel into the engine.
It`s like the old type `choke` systems.
Get it checked at an auto electricians.

i recommend cleaning the throttle plates. they are located unter the intake hose form the engine to the air filter housing. if you open them with the engine not runniong you will see they will be covered in carbon. use a good carb cleaner and a rag to wipe them clean

Here is the most common cause of surges and stalls and low idle rough idle, it is the idle speed control air-bypass valve and throttle valve (IAC for short), they get full of gunk over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.

Here is the most common cause of surges and stalls, it is the idle speed control air-bypass valve and throttle valve, they get full of gunk over the miles and cause idle issues (stalls) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.

it all depends on what yr the ford is b/c my grandmas car dose it a lot when you go to shut the car off make sure it is in park and it is in a idle then when you start it it should be fine if not go under the hood and see if it accelator can be lossened a littel bit if so it will save you on gas and the idle wont be as high. if that dose not work then dont worrie about it it wont harm the car any and dont pump the gas pedall while the car is not running