My car idles bad, why?

Question

A few days ago, my car was in park and started to shake lightly. I gave it gas and it was ok. The next day, it did it more. Not when I drive, only when stopped w/out gas. Then I stopped short at a light, and it shook and stalled and the check engine light came on. I went straight to autozone and they hook it to the machine. It said "system lean". The guy said its either plugs and wires(changed'em, same problem) or my O2 sensor. I bought a new O2 sensor but a friend of mine said its not that. He said it was my MASS AIRFLOW SENSOR or MAP SENSOR. What does it sound like? {check engine light on*system lean reading*shakey idle , when car is warm*only shakes or stalls when stopped}

2001 Ford Focus SE

Answer 1

Get and oil change and a transmission flush!!

Answer 2

First of all Autozone only reads codes to sell you parts that you might not need.

Second you have too many systems failing.
The componet that tells the computer that the engine is warm to bring it out of cold "closed loop" is the coolant temperature sensor.

But before you replace any parts take to somebody else and have the alternator and battery tested. When the battery voltage gets low the computer will shut the engine down, or you don't have enough power to run all systems.

In the event you hav added a powerful stereo, you might need to go with a more powerful battery and/or add another dry cell in the trunk.

Answer 3

It could be that the throttle plate isn't closing all the way at idle, due to buildup on the throat where the butterfly plate closes. This causes too much air to be drawn in with not enough fuel, or a lean condition.

Get some carb cleaner and clean up the inside of the throttle body where the plate is. See if that works, and it'll only cost you a couple of bucks.

It could be the O2 sensor as well. This is the reason I own my own code reader.

Answer 4

did you check the air filter? it could be dirty if you haven't done that in a while. It could possilbly be the airflow sensor. It's about the size of a credit card on my truck. The sensor could just be dirty too. The filter is a piece of cake to change, cheap too. The sensor might be harder to find/remove and might cost a few $$ if its.bad.

Only reason I say the sensor is cuz I put in a K&N intake and accidentally put the sensor in backwards and the truck stalled 2 seconds after starting...until I flipped the sensor and bingo--no problems.

Answer 5

Unfortunately, it can be many things on these newer cars these days. Since the advent of "electronic" control, you pretty well have to take the car back to the dealership and have them work on it. Problem could be MAP sensor, O2 sensor, cataletic converter shot, plugs and plug wires, and the damn list goes on and on and so does the price. Even the garage gurus can't give you a definite answer or narrow it down to one item...!! So they replace until they get the right one, at your expense. By a pre-1988 vehicle.

Answer 6

ha ha ha that guy is stupid yea that really is going to make it run right. No honey its most likely mass air flow or the Map sensor. If you want to know which one it is or if it is either of them. Disconect one and drive it see if it makes a difference. If it runs better then its that sensor if it runs crappier or the same connect it and disconect the other sensor. If both sensors seem to be ok I'd check your fuel pump, fuel filter or fuel pressure regulator. good luck with it car is starting to get old.

Answer 7

UGH!
Mine is doing the same thing...
I took it back to the dealer, & they told me it's the air flow...& it needs a new valve for that, to the tune of about $600.00!! (Don't remember exactly what they called it---my ears were ringing after the mention of the cost...!)

So, every time I come to a stop, if it starts to shimmy & shake, I pop it in neutral, then put my left foot on the brake, & gently keep right foot on the gas. Takes some practice & coordination, but I'm getting pretty good at it!
And I look on the bright side---if anyone ever tried to steal my car, they sure wouldn't get too far! LOL!!
Good luck!

Answer 8

actually it could be the o2 sensor because its reading that ur engine isnt running right and trying to fix it there fore making your engine run lean. Try the o2 sensor first.

Don

Answer 9

It sounds like a leaky intake manifold gasket. It will let more air in at low manifold pressures (like at idle) and seal back up at normal engine speeds.