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2005 Malibu 4Cyl Idle Issues

28791 Views 15 Replies 4 Participants Last post by  Mrfixit

When starting car the idle runs rough and then will eventually die. Will die at stop lights. If I press the gas while at a stop I can keep it running by shifting to neutral or going to park.

Err Codes: P0300, P0442

What I have done since(with no resolution):
1. Cleaned Throttle Body
2. Cleaned the Mass Air Intake Sensor(in front of air filter)
3. Replaced Ignition Coil
4. Replaced Spark Plugs
5. Replaced wireset
6. Replaced Ignition Control Module
7. Checked the Fuel line pressure and is registering 58-60psi.

My ideas are

1. The Throttle Position Sensor(TPS) is bad an thus will need to replace the entire throttle body.(Autozone does not have the Throttle Body).
2. Intake Manifold leak/vacuum issue

I am not a mechanic, fast learner, trying to resolve this.

Any help is very appreciated.
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Welcome to the forum.:) It sounds like an air leak. How did the spark plugs look? Do you have freeze frame data to go along with P0300? Did this problem suddenly show up? Accident history, current mileage, aftermarket modifications?
You can use any carburetor or throttle body cleaner spray cans (they come with a thin plastic nozzle). Read a pharagraph or two at Also, ask if she got some gasoline at a service station that's not her usual one. Sometimes all that's needed is a bottle of fuel system cleaner and full tank of fresh gas.
The old spark plugs don't seem to be fouled (no carbon on the insulator, no soaking oil residue), as far as I can see.

There's no PCV valve on the 2.2L, just a PCV hose that goes between the camshaft cover and the intake manifold. See^5L61^6.gif. You can try taking the hose off of the intake manifold nipple and plug it (the nipple, not the hose, of course) to see if the PCV plumbing is the source of the air leak.

If unplugging the MAF sensor made a difference, maybe there's a wiring problem (although usually there should be one or more DTCs with the malfunction indicator). Try feeling for a soft spot along the MAF/IAT sensor wiring with the engine running. If you're lucky, you may hit a spot where the idle problem gets better/worse. You can also check each wire/terminal separately with a multimeter. See the powertrain wiring diagrams:

BTW, these are for 2005 Malibu with 2.2L, not Malibu Classic.
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Shoot, something was bothering me and I just realized what it was. The PCV hose you see is the breather side. If you try unplugging the PCV hose, you'll want to plug both the hose and the nipple or you'll create a huge source of air leak.:(
Are you sure? I guess I dodged a bullet since I've never needed a 5-point star torx tamper proof security bit. And, I've got my share of tools I bought and used once and only once.:eek: Anyway, the reason I mentioned the wiring problem was because everything was fine with the MAF/IAT sensor connected and then the problem returned while driving (vibration).
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