No brakes in the morning. It will definitely wake you up more than coffee.

Last night I started up the car to do the vacuum leak test and the engine stumbled a bit and almost stalled out and notice the check engine light on. New codes! P2279 Intake Air System Leak and P0507 Idle Control System RPM Higher Than Expected. Petrified.rabbit I can already sense your head shaking at me lol.. This is the first time these codes came up. I continued with the propane torch on all the vacuum lines and wouldn't you know it there was no change in RPM! It did accelerate on it own tho. I thought I found a leak but the engine stayed at that RPM and didn't come down. I went over a few more times over the PCV hose, the two small vacuum hoses and the booster hose. No change or fluctuations in RPM. I'll try it again this evening when I get home. As for the brake booster this was replaced for the same problem I've been having. This was replaced back in April and bought at the Chevy dealership AC Delco brand. Of course the problem continued as it did with the old booster. This later was led by the replacement of the master cylinder. Again, same problem and symptoms. Master cylinder was diagnosed by the tech at the dealership who said that was the issue. Of course it was not and even purge the system twice for air. The problem that this car has been having is sudden loss of braking power. Like as if the booster didn't have vacuum or something. The brake pedal would go stiff and your need extra effort to stop. But it doesn't always happen. It's random and no real pattern to it other than it used to happen in the mornings when you start the car. After driving about a block braking works like always and quick to stop. I drove the car for a week and it never happened to me except for once when I was backing out of the drive way and the pedal got stiff for a 2 seconds and returned back to normal braking. Even the tech at the dealership could not replicate the issue even after leaving the car sitting in the lot all day. But with these new codes we are getting closer I hope.

Also I forgot to note that back in April I did have the throttle body replaced at the dealership. The problem there was the engine was idling fast. Sometimes it would idle up to 2000 RPM and stayed there. Even if I step on the gas a bit it wouldn't come down. The tech checked it out and said someone had messed with it and adjusted a screw on the throttle body. Got it replaced and solved that problem. Car is idling as it should since then but now it's acting more like a vacuum leak which is confirmed by the new codes now.

Think there is a rubber tube / hose that connects the air filter box to the throttle body . Look at that tube / hose ( maybe 3" diameter ) . Common fault for AVEO and Sonic to develop cracks / splits .

I think this is the revised GM part # for the Sonic ?

Chevrolet GM 12 15 Sonic Air Intake Outlet Duct 94537633 | eBay

Not sure for the part # for AVEO ?

God bless
Wyr

Yours is a 2005 AVEO ? Rockauto.com seems to have it .

2005 CHEVROLET AVEO 1.6L L4 Air Cleaner Intake Hose | RockAuto

If it is the duct ( what they are calling it ) , the idle air control problem may disappear when you replace the duct ?

God bless
Wyr

Hi WyrTwister! I forgot to mention that duct was replaced at the same time along with the throttle body last month. The old one did have a crack in it. So it's pretty much new everything between the intake manifold to the air filter box. Well not the small hoses of course. Throttle body came with a new IAC too. But I will check again just to be sure and check the bolts on the throttle body. I feel like i'm rebuilding the car a piece at a time lol..

Check to see if the TB and every thing is secure . I think maybe the small hose may supply filtered air ( before it reaches the MAF sensor , to the engine . If so , that air circulates through the engine , purging fumes from the engine & is in turn pullet out through the PCV valve and into the intake manifold . All other air should be measured / sensed by the MAF sensor before it enters the throttle body .

If you have a air leak past the MAF , it is called Pirate Air , since it is not measured / sensed by the MAF & the computer does not " know " about it . This messes up the air fuel mixture , which the O2 sensor should pick up . The computer tweaks the idle air control valve and the air fuel mixture to try to correct , based on the info / data from the O2 sensors .

Or , something along these lines .

Check any electrical connectors on the IAC valve & TB . And any other parts that were disturbed .

How many miles did you say you had on the car ? Does sound like you are rebuilding the car 1 part at a time . :-(

Ours is a 2015 Sonic . I hope , long term , it has fewer issues than the AVEOs .

God bless
Wyr

PS Check the hose clamps on the duct and any others you see . Check to see if any duct or hose has slid off its respective connector . Or sensor .

Quote:

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Originally Posted by WyrTwister

Check to see if the TB and every thing is secure . I think maybe the small hose may supply filtered air ( before it reaches the MAF sensor , to the engine . If so , that air circulates through the engine , purging fumes from the engine & is in turn pullet out through the PCV valve and into the intake manifold . All other air should be measured / sensed by the MAF sensor before it enters the throttle body .

If you have a air leak past the MAF , it is called Pirate Air , since it is not measured / sensed by the MAF & the computer does not " know " about it . This messes up the air fuel mixture , which the O2 sensor should pick up . The computer tweaks the idle air control valve and the air fuel mixture to try to correct , based on the info / data from the O2 sensors .

Or , something along these lines .

Check any electrical connectors on the IAC valve & TB . And any other parts that were disturbed .

How many miles did you say you had on the car ? Does sound like you are rebuilding the car 1 part at a time . :-(

Ours is a 2015 Sonic . I hope , long term , it has fewer issues than the AVEOs .

God bless
Wyr

PS Check the hose clamps on the duct and any others you see . Check to see if any duct or hose has slid off its respective connector . Or sensor .

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The Aveo has 166k on it so it does need a little tender loving care. Body of the car is intact and no rust but then again here where I live we never get snow. Well we did once back in 2005 for about an hour. lol.. If I don't find any leaks with the propane torch then it's time to build my own smoke machine!

Attachment 10347
The little Aveo I am working on... and yes, it has red painted calipers and drums. lol..

Quote:

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Originally Posted by jamesd

The Aveo has 166k on it so it does need a little tender loving care. Body of the car is intact and no rust but then again here where I live we never get snow. Well we did once back in 2005 for about an hour. lol.. If I don't find any leaks with the propane torch then it's time to build my own smoke machine!

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Jamie, did you put a gauge near the booster? And tried breaking when cold? You don't have to be moving just see if it maintains the same vacuum as a warm setup.

Quote:

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Originally Posted by xintersecty

Jamie, did you put a gauge near the booster? And tried breaking when cold? You don't have to be moving just see if it maintains the same vacuum as a warm setup.

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No I haven't yet. I don't get home until 8pm so by then it's dark to see what I am doing. I am hoping to do that with what little light there is in the evening.