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2006 chevy cobalt erractic idle
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Clayton1000
New User
Aug 13, 2013, 5:24 PM
Post #1 of 7
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2006 chevy cobalt erractic idle
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Hello. I have a 2006 Chevrolet cobalt, engine 2.2, mileage 110,000. My cars idle fluctuates and sometimes stalls.
This problem has started about 6 months ago and has gradually gotten worse. There has been no trouble codes from the computer. When I press on the gas the car hesitates for a moment and the runs great. I have the Haynes repair manual which which suggests checking the PCV system. It's instructions lacks clarity so here i am asking for help on this forum.
Following the books instructions i removed the PCV hose and checked for a vacuum? Which port? On the engine port or the air intake system port? I put a vacuum gauge to the engine port and I got a very slow pulsating pressure increase which is normal to me as blow by past the piston rings. If there is supposed to be a vacuum at the engine port (in the crankcase?) as the book implied, where is this vacuum coming from? I did not finish this test and will later check to see I have a vacuum at the air intake system port which I think would be normal.
Nothing that has been done to this car has shown an improvement. Here is what has been done in the last couple days. The MAP sensor has been replaced from a junkyard. The MAF sensor has been removed and cleaned twice with a spray can of MAF cleaner. I sprayed the throttle body with a spray can of carburetor and choke cleaner. Here is what has been done in the last 6 months. A new air filter, fuel filter, and spark plugs. If I hit the problem will I see an immediate improvement? Does the computer need to be cleared by disconnecting the battery?
Any suggestions to help me solve this erratic idle problem will be greatly appreciated.
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Discretesignals
Ultimate Carjunky
/ Moderator
Aug 13, 2013, 5:47 PM
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Re: 2006 chevy cobalt erractic idle
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You should take it to a shop that can access datastream information. Looking at datastream information might give some clues as to what is going on. They could also smoke check the engine for vacuum leaks that you may not see using conventional methods.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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Clayton1000
New User
Aug 18, 2013, 11:04 AM
Post #3 of 7
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Re: 2006 chevy cobalt erractic idle
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Thank you for responding!
As I went to complete the testing for the PCV system I noticed that the air intake had oil inside. The engine was sucking oil into the air intake through the PCV hose. I checked the engine oil level and the oil level was above the max mark on the dipstick. The car was taken to a garage that does nothing but change the oil. The car was almost due for an oil change. They said that this engine takes 5 QTS of oil and put 5 QTS of oil in the engine. After the oil change I checked the book and they were right, this engine takes 5 QTS. I checked the dipstick over and over again and the oil level was above the max mark on the dipstick. The next day I drained just over a QT of oil out of the engine putting the oil level on the dipstick ¾ of the way full. I wiped the oil out of the air intake. I took a toothbrush and carburetor cleaner and cleaned OIL out of the throttle body. The car now idles perfectly.
Take care Clayton
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Hammer Time
Ultimate Carjunky
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Aug 18, 2013, 1:26 PM
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Re: 2006 chevy cobalt erractic idle
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This engine takes 5 quarts with the filter. Running it low will do harm to the engine.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
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Aug 19, 2013, 4:57 AM
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Re: 2006 chevy cobalt erractic idle
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Clayton - some questions, thoughts about this: I can't think of anything more important to an engine than proper oil, oil pressure and level. It is TOTALLY worth paying attention to and always was. Changing it on manufacturer's schedule listed in car's manual OR many will suggest 3 months or 3,000 miles whichever comes first.
Seems everyone is pretty sure that 5 quarts with filter is the proper amount.
I'm still concerned that you found oil in the intake. To me that's a terrible sign and worth total investigation as to why. Many PCV systems operate on the same basic ideas for decades on end now. Some blow by is going to happen such that all that fumes in crankcase sealed areas are polluted air with oil mist frequently in it so the idea is to burn that off in a metered manner that a PCV valve does using manifold vacuum. It also should separate out oil mist as a system and pick up filtered air in some manner to replace the vapor removed done in assorted ways but to achieve the same goal.
When/if blow by exceeds what the PCV system is burning off you can get pressure instead of slight vacuum in crankcase sealed areas that are all thru up to the valve cover(s) and any remote oil fill caps and so on. When pressure is there either clogged PCV hose to it or however done many can send the mist backwards ending up in a puddle that you did just spill there.
It's not my place in this world to bash the oil change only places but they haven't had the best history at least local to me when the idea became popular and no argument it's handy for customer's.
The scare is some are advertising how fast they can change oil down to a 10 minute guarantee! WHAT! Have come to find out they are sucking oil out thru dipstick tubes not even touching a drain plug! Now I'm more scared and can't believe that gets all of it or dependable vehicle by vehicle types. Marine engines using automotive type engines did plan on that - different reasons and not this issue.
There's a chance of getting the wrong dipstick IMO with this rat race oil changing. Drain plugs stripped, caps left off. Wrong fluids put in topping things off, leaving an oil filter gasket stuck on engine from old one and the list goes on.
Can you change your own oil at least once letting it drain for a good while, filter too, measure and know you have the exact amount, run engine to circulate then let it sit level for at least 15 minutes and see if it's on the right mark?
I've done that to all (100s over the years) of my own assorted vehicles all used and found many wrong to WAY wrong! Would even purposely only fill to read one quart low and see if that mark is right too. You can't do that in quick change places - no time for it. That was also to check if ones with an oil level warning system really warned you if you were really ONE quart low. Most don't! Has to be more than one quart too low if they work so I don't trust that bull on new or older vehicles.
One more and enough of this novel - sorry. The dipstick is also a seal for the crankcase.
The subject is too important to ignore. Too many perfectly good engines have been destroyed by things going wrong,
T
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Clayton1000
New User
Aug 21, 2013, 4:12 PM
Post #6 of 7
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Re: 2006 chevy cobalt erractic idle
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Thank you all for responding!
Even though I stated earlier that this car is MY car, its not really and I was not the one who regularly checked the fluids. With that being said, I have no comparisons as to whether or not there was an issue with the oil level right after an oil change in the past.
This car has had regular oil changes (every 3000 miles) at the same oil change business. I am suspicious that their oil regulator that they set to 5 qt s may be faulty or the guy in the pit did not let all the old oil drain out and I had not returned there to inform them about this issue. I would suspect that they would have been aware this by now if this has been an ongoing problem for 6 months.
I have continued to check the oil and the oil level is still at 2/3 up to the full mark on the dipstick. When it comes to a choice between the book specification or the dipstick I can't ignore the dipstick. This car was purchased 2nd hand with very low mileage and the previous owner was a car rental business. With this having been said I'm finding it hard to believe that this car has the wrong dipstick. The car has continued to idle perfectly and no oil in the air intake. I have not found a reason to believe that engine coolant is ending up in the oil pan.
The next oil change will be done at home so we can see if there is a problem with the oil capacity.
Here's something interesting to consider!
When I took the car to the oil change place I told them that I'm troubleshooting a rough idle problem and their reply was we see a lot of that with this model.
I was told by employee at an automobile auction that every Chevy Cobalt that passed through there had a rough idle problem.
Take care Clayton
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Tom Greenleaf
Ultimate Carjunky
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Aug 22, 2013, 1:26 AM
Post #7 of 7
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Re: 2006 chevy cobalt erractic idle
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Quote ">>I was told by employee at an automobile auction that every Chevy Cobalt that passed through there had a rough idle problem. <<"
Perhaps the have a propensity was told by employee at an automobile auction that every Chevy Cobalt that passed through there had a rough idle problem. Is this to say they make the same mistakes over and over or are better trained at excuses?
Agreed, the dipsticks are the way to go to be sure but know it's the right dipstick.
BTW - if coolant was getting into oil it would froth up like a milk shake. Fuel can get into oil and make it so thin and too full you get cylinder wash/wear and destroy an engine.
If they have faulty equipment and are not checking it's negligence on their part. Makes you wonder if they are motivated to care,
T
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