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Old 09-09-2010, 04:35 AM   #1
A1y50n
Scooby Newbie
 
Member#: 130194
Join Date: Oct 2006
Chapter/Region: SCIC
Location: SoCal
Vehicle:
2007 Impreza 2.5i SW
Newport Blue Pearl

Default Searched through threads, please confirm findings

Hello all,
I should have done my research before purchasing an intake system. My bad.
So I have a car that won't idle properly when I press the clutch while slowing down. Here's what I've found regarding this problem.

1. I need to check for vacuum leaks
My understanding is that there are 3 vacuum lines connected to the intake system, 2 that go into the engine near the spark plugs (1 on each side), and 1 that is connected to a white plastic sensor thingy that goes into the engine around the middle area.
I also understand that my 07 2.5i does not have the idle air control valve so it does not concern me.


2. The MAF is not at fault.
If it were, I would have CEL codes, which I do not. (By the way, as I was cleaning the MAF sensor with the CRC spray, I noticed that the tip of the electrode bulb is amber/brown. Is that normal?)


3. I need to rescale the MAF map.
No matter how much I let the stock ecu learn the new settings, it will not be able to compensate for the intake and continue to have un-idleable AFR. Tactrix is on it's way and I am eager to look at the current afr values and hopefully figure out how to scale it properly.


4. The O2 sensors are not at fault.
Though a faulty o2 sensor can give incorrect data to the ecu and cause the engine to stall, it will always throw a CEL. Since there is no cel, the o2 sensor can be assumed to functional.

This is information I've found so if I wrong, please let me know.


Question 1.
Since our ecu detects the afr through the amount of oxygen read in the exhaust O2 sensors, why am I not getting a CEL for running too rich if that is in fact what's causing the engine to stall?

Question 2.
I've read that not the engine should idle even without a working MAF sensor. If this true? The implication would mean that my engine is not idling because of a reason other than the afr.

Question 3.
Why does the engine stall only when I depress the clutch? Is there a separate idle controller for the 07s (that physically sets the idle) or is it all based on a map in the ecu (software)?

Any help or pointers are appreciated.
I'd like to drive my car to and from work without turning the ignition or roll starting the car three dozen times.
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Old 09-09-2010, 06:30 PM   #2
kewlboxer2
Scooby Newbie
 
Member#: 161322
Join Date: Oct 2007
Chapter/Region: Tri-State
Location: Galeton, PA
Vehicle:
06 2.5i
Regal Blue

Default

Mine did that when the MAF scalling was crazy off. After a couple days it sorted the idle out. An intake will not make the car rich. It will make lean in 2 ways.

1.) More air flow.

2.)With no Snorkus you WILL be lean in lower RPM's this has been documented by Williaty. He "invented" the hybrid intake to care of that issue.

The car will run with no maf. Ive done it before when I took my maf out overnight to clean and the dog used it as a chew toy($300).

There is an Idle speed control valve on the throttle body, but usually letting it idle for 15 min after a ecu reset will fix low idle, unless the maf scaling is bad.
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Old 09-09-2010, 08:42 PM   #3
formula91
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Member#: 102984
Join Date: Dec 2005
Chapter/Region: MWSOC
Location: Northbrook, IL
Vehicle:
2005 2.5RS 4EAT
Platinum Silver

Default

Quote:
Originally Posted by A1y50n View Post
Hello all,
I should have done my research before purchasing an intake system. My bad.
So I have a car that won't idle properly when I press the clutch while slowing down. Here's what I've found regarding this problem.

1. I need to check for vacuum leaks
My understanding is that there are 3 vacuum lines connected to the intake system, 2 that go into the engine near the spark plugs (1 on each side), and 1 that is connected to a white plastic sensor thingy that goes into the engine around the middle area.
I also understand that my 07 2.5i does not have the idle air control valve so it does not concern me.


2. The MAF is not at fault.
If it were, I would have CEL codes, which I do not. (By the way, as I was cleaning the MAF sensor with the CRC spray, I noticed that the tip of the electrode bulb is amber/brown. Is that normal?)


3. I need to rescale the MAF map.
No matter how much I let the stock ecu learn the new settings, it will not be able to compensate for the intake and continue to have un-idleable AFR. Tactrix is on it's way and I am eager to look at the current afr values and hopefully figure out how to scale it properly.


4. The O2 sensors are not at fault.
Though a faulty o2 sensor can give incorrect data to the ecu and cause the engine to stall, it will always throw a CEL. Since there is no cel, the o2 sensor can be assumed to functional.

This is information I've found so if I wrong, please let me know.


Question 1.
Since our ecu detects the afr through the amount of oxygen read in the exhaust O2 sensors, why am I not getting a CEL for running too rich if that is in fact what's causing the engine to stall?

Question 2.
I've read that not the engine should idle even without a working MAF sensor. If this true? The implication would mean that my engine is not idling because of a reason other than the afr.

Question 3.
Why does the engine stall only when I depress the clutch? Is there a separate idle controller for the 07s (that physically sets the idle) or is it all based on a map in the ecu (software)?

Any help or pointers are appreciated.
I'd like to drive my car to and from work without turning the ignition or roll starting the car three dozen times.
Answer to Question 1:
Your assumption about the O2 Sensors not being at fault are not completely true. Once O2 sensors become inaccurate enough, they will throw a CEL. However, they were most likely going bad weeks or even months before the CEL would even show up. However, as O2 sensors go bad, they report a lean condition, therefore your car will mistake your normally stoich/target AFR, and then you car will in actuality be rich.

A to Q2:
Your car can run without an MAF. Your CEL will be on and you would not be able to rev past 3k. Just take the connector off your MAF and see.

A to Q3: I'm not quite sure as to why, but have you checked your fuel filter?
The other possibility is the Occam's Razor -> Your clutch is the problem. Your clutch might need to be adjusted. If it stalls when pressing brakes, it could be the vacuum booster.


Some other stuff.
Your car is able to adjust for the intake... somewhat... there is a set maximum to it, but it can adjust so long as the values are not so different. The intake can cause problems beyond that of which the ECU is able to adjust fueling for. This only affects closed-loop fueling, and NOT open-loop. Open-loops will be subject to the full range of problems. Therefore, your problems may be more pronounced when you really step on it or go WOT.
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