TO JOE. THANKS FOR YOUR ANSWERS TO MY PREVIOUS QUESTIONS

MYCAR78

MEMBER
2005 CHEVROLET COBALT
2.2L
4 CYL
2WD
AUTOMATIC
140,000 MILES

To JOE. Hey Joe its DAN again. I have a 2005 Chevy Colbolt 2 door coupe 2.2L Automatic.
I want to thank you for you spot on answers about when my check engine light came on with the Codes ( PO 171 and PO 455 ).

I wrote down everything you replied your answers to my questions step by step for my mechanic.
I will be bringing him my car on MONDAY 1/12/15 to fix those issues with my car.

Now I have a couple of more Questions for you JOE.

TODAY ON SATURDAY 1/10/15 I started my car for the first time this morning and I let it warm up for 15 minutes.

Megan I started my car the ( CHECK ENGINE LIGHT WAS STILL ON ) obviously because I haven't yet had those problems fixed yet. However I went to mcdonalds today after I started my car for the first time today. After I was done at McDonald's, my ( CHECK ENGINE LIGHT WENT OFF ).
So I found that to be strange, I thought maybe the ( CODE PO 171 system to lean bank one cleared its self up on its own ). However when I got home, I took my OB2 SCANNER AGAIN AND SCANNED MY CAR AGAIN.

THE SAME CODES ( PO 171 and PO 455 ) still were showing on my OB2 SCANNER EVEN WITH THE CHECK ENGINE LIGHT OFF. So I definitely know that there are those problems that you said there were according to the codes I told you. I will get them fixed on MONDAY 1/12/15.

QUESTIONS.

QUESTION 1--- ( ON MY OB2 SCANNER FOR CODE PO 455 THE EVAPERATIVE SYSTEM I WENT TO THE OPTION WHERE IT SAID ( DIAGNOSIS OF ACTUAL PROBLEM ACCORDING TO TGE CODE IN MORE DETAILED FORMATE.

IT SAID ( EVAP ( VP ) ( H20 ). THEN IT FLUCUATED BETWEEN TWO SPECIFIC NUMBERS.
THE NUMBERS WERE ( 6.082-6.087 ) and they were going back and forth back and forth back and forth.
NOW I ALREADY KNOW WHAT THE CODE DIAGNOSIS IS ACCORDING TO YOUR ANSWER FROM MY PREVIOUS QUESTION BUT LIKE I SAID I WENT A LITTLE MORE IN DEPTH.
SO WHAT DOES ( EVAP ( VP ) ( H20 ) MEAN?
AND WHAT DO THE TWO NUMBERS THAT KEPT ON FLUCUATING BACK AND FORTH MEAN? THE NUMBERS AGAIN ARE ( 6.082- 6.087 ) THOSE TWO SPECFIC NUMBERS KEPT GOING BACK AND FORTH ON THE ( OB2 ) SCANNER WHAT ARE THOSE TWO NUMBERS?
ARE THOSE TWO NUMBERS INPORTANT?
WHAT IS NORMAL AND NOT NORMAL ABOUT THOSE NUMBERS?
ALSO WHAT DOES ( VP ) MEAN AND ( H20 ) MEAN?

QUESTION 2 WHAT DOES THE ( EVAP PURGE MEAN )?
THERE WAS ONE SPECIFIC NUMBER SHOWING ON MY OB2 SCANNER AND THE NUMBER WAS ( 12.9 ).
WHAT DOES THAT NUMBER MEAN?
IS THAT NUMBER NORMAL OR NOT NORMAL?

QUESTION 3---- GOING MORE IN DEPTH AGAIN WITH MY OB2 SCANNER IT SAID ( FUEL SYSTEM 1 -- CLOSED ) ( FUEL SYSTEM 2 NOT APPLICABLE )
WHAT DOES IT MEAN FUEL SYSTEM 1 CLOSED?
ITS THAT NORMAL? OR IS THATCA VERY SERIOS PROBLEM?
NOW IT SAID FUEL SYSTEM 2 N/A NOT APPLIABLE I AM ASSUMING THAT STANDS FOR?

Now when I drive my car everything seems to be running fine and smooth while driving.
Everything also seems to be normal while sitting at a traffic light fully stopped also while ideling.
Nothing seems out of the ordinary, but I know that my mechanic needs to do what you said he needs to check with the CODES.

HOWEVER I DID NOTICE WHEN THE CAR IS IDLING WHILE IN ( PARK ) WHEN THE CAR IS ON THE THE ENGINE IS VERY BOUNCY AND IT'S JUMPING AROUND A LOT WHILE THE CAR IS ON AND IN ( PARK MODE ).

DOES THAT HAVE TO DO WITH THE CODE ( PO 455 ) EVAPARATIVE SYSTEM ( VACCUM LEAK AND A HOSE LEAK )?

AND OR DOES IT HAVE TO DO WITH THE FUEL PRESSURE SINCE I PUT THE INJECTOR CLEANER IN WITH HARDLY ANY GAS IN THE CAR POSSIBLY CAUSING THE FUEL PUMP TO BE DANAGED OR THE FUEL FILTER BEING CLOGGED?

BUT HOW COME THAT ONLY IS HAPPENING WHEN THE CAR IS IN ( PARK MODE WHILE THE CAR IS ON ) AND EVERYTHING ELSE WHEN DRIVING AND SITTING AT A TRAFFIC LIGHT IT DOESNT DO THAT THEN?
BECAUSE WHEN I DRIVE AND WHEN I AM SITTING AT A TRAFFIC LIGHT EVERYTHING FEELS AND SEEMS TO BE NORMAL, NO HESITATION, NO STUTTERING NOTHING LIKE THAT HAPPENS WHEN I AM DRIVING AND WHEN THE CAR IS IN ( DRIVE MODE WHILE IDLING ITS RUNNING SMOOTH?

ALSO WHEN I TURN MY HEAT ON, THERE IS A WEIRD NOISE COMING FROM UNDERNEITH THE GLOVE CONPARTMENT, I CANT EXACTKY DESCRIBE THE NOISE, ITS SOUNDS LIKE A WISSING NOISE WHEN I TURN MY HEAT ON AND THE NOISE IS COMING DIRECTLY UNDERNEITH THE PASSANGER SIDE GLOVE BOX COMPARTMENT.
WHATS THAT NOISE COMING FROM?

PLEASE CONTACT ME BACK AS SOON AS POSSIBLE WITH YOUR EXPERT ANSWERS AND EXPERT ADVISE AND EXPERT ANSWERS TO ALL MY QUESTIONS I PROVIDED TO YOU PLEASE.

PLEASE CONTACT ME BACK AS SOON AS POSSIBLE.

AGAIN THANK YOU VERY VERY MUCH,

DAN

3 Replies

MHPAUTOS

MECHANIC
31,937 POSTS

I will not jump in on this question, but the best way to get in touch with the tech that has been helping you is to re post on the original thread, he will get an in bot to alert him there is another post from you, he may not see the new post.

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Sunday, January 11th, 2015 AT 3:10 AM

CJ MEDEVAC

MECHANIC
11,005 POSTS

MYCAR78

I JUST SENT J & N A MESSAGE

I INCLUDED A LINK TO "HERE"

THE MEDIC

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Sunday, January 11th, 2015 AT 10:55 AM

JACOBANDNICKOLAS

MECHANIC
109,913 POSTS

Dan:

I am so sorry I didn't see this post. CJ emailed me otherwise, I still may have missed it.

Okay. Question 1:

I will try to explain how the EVAP system ties in with the PCM. The PCM commands both the EVAP Purge Solenoid and the EVAP Vent Valve to the on mode when the conditions are met. This is done in order to apply an engine vacuum to the EVAP system. The PCM commands the EVAP Purge Solenoid OFF once the system has reached a predetermined level of vacuum. If a predetermined level of vacuum can be reached, that indicates a leak in the system and the code is set. The lean mixture could be the result of this test that the vehicle does itself. As far as the check engine light going off and then on, the system may have met the requirements needed and turned the light off only to fail again and turn back on. Often times the light can be off but there are codes that are pending, which basically means the system had a code and is waiting to see if it continues to work. Once so many cycles are performed by the PCM, the code will then be gone.

The numbers you referred to I believe are the O2 sensor readings while the engine is running and don't seem too far out of line.

Question 2:

The purge solenoid is basically the item that allows gas vapors to enter the engine. This is usually where the problems start with these systems. If they don't work properly, they can produce a few different codes. My honest belief is the purge solenoid is what is setting the code for the EVAP leak. As far as the 12.9, I believe that is the voltage going to the purge solenoid and that is normal.

Question 3:

As far as the rough idle, chances are that is the result of a vacuum leak which is also causing the lean fuel mixture. An open loop is basically when the car is first started and the oxygen sensors are not warmed to operating temp. In this situation, the computer runs the vehicle based on other factors such as air intake temp, mass air flow sensor. Things basically run on a programmed default setting. A closed loop is when the computer can determine how much fuel to give the engine based on exhaust gasses. The car should use both systems, but when it warms up, it should be in a closed loop.

Question 4:

As far as the noise you hear from under the dash when the heater is used. To me that sounds like yet another vacuum leak. The vent doors in the HVAC system that direct air flow are actuated by engine vacuum. Based on your description, that sounds like what it is.

I hope I answered all your questions. Let me know if you have more and just add them to this post so I get the notification right away. Again, I'm sorry for the delay.

Let me know you received this. By the way, the website policy is that we can't email directly to someone. That is why I had to do it this way.

Joe

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Tuesday, January 13th, 2015 AT 6:32 PM