aveo stalls on restarts only after it is warm

[drewd]

hi...new to the site ...but i have been searching for an answer for my 2004 automatic aveo....couple of years ago it started stalling ...but this happens only when it is warm....and only after i have turned it off for a few minutes...like going shopping....when i return ....car starts right up ...but when i accelerate it will not shift into the next gear and will die.....the only way i can save it from doing this is by shifting into neutral and revving the engine.....once it does get going it will not show these symptoms unless i turn it off and wait a few minutes......so again....never stalls when starting cold..only after it is warm....will start and idle fine...but if i accelerate it will go to about 25-30 k rpm and then lose power....only way to stop it from stalling is to shift into neutral and rev it pass those rpms....then it is fantastic for rest of the drive....never dies at lights etc
problem is worse in the summer than in the winter

other facts
gets between 22-28 mpg depending on season..i was hoping for better when i bought it
ive changed spark plugs
cleaned throttle body

ive tried to clean the iac valve but couldnt get it off

replaced air filter
no codes ..no check engine lights


any ideas from the pros out there?....im not very car savvy....thanks for any futre help w/ this drew

[avguy]

A couple of years is a long time for something like that to keep on happening without getting worse. Not a pro, but it sounds like a bit of vapor lock. But the fuel lines are away from the exhaust, so unless some customization was done which moved them into closer proximity, that doesn't seem too likely. A temporary exhaust block would do the same thing, but it's hard to imagine that happening with a stock exhaust system.
Most of the other things that come to mind as possibilities all seem like they should get worse over such a long time period. Why weren't you able to remove the IAC? It's a tight space, but the 2 screws should never be rusted, and will turn out easily if the right tool is used.
Have you tried reving it way up and let it drop down to normal rpm a few times after warm starting, but before trying to drive? Does anyone you know own a real-time scanner that you could borrow? They can sometimes provide data which enables you to zero right in on the problem.

[drewd]

thanks for the quick reply...
ive tried to take iac myself but screws were facing to the back and it looked like i would need a special tool or take out alot of other stuff that i didnt feel comfortable about...
.i have a generic scan tool and can hook it up but could you tell me specifically what data i should be looking for?
i have tried the revving on start up but it doesnt seem to work...maybe because i have in park instead of neutral?
another fact i forgot to add....i found the watchmacallit from my air filter to throttle body was ripped right open...who knows for how long...but i had it fixed...but no change in issues

[Aveo5_boy]

i found the watchmacallit from my air filter to throttle body was ripped right open

Air Intake Hose.

[drewd]

Air Intake Hose.

there you go

[avguy]

I used a mini 3" handle ratcheting driver with a #2 bit to remove the IAC on my '05. If you need to buy something this looks like it would do the job nicely.
8 Piece Right Angle Screwdriver

AFA the real-time data goes, fuel trim would always be of interest. Because it's running well other than the stall, the data values would probably not be abnormal. I'm thinking that if anything in the data stream changes just prior to the stall, that might be helpful information in diagnosing the problem.

[enflux75]

hi...new to the site ...but i have been searching for an answer for my 2004 automatic aveo....couple of years ago it started stalling ...but this happens only when it is warm....and only after i have turned it off for a few minutes...like going shopping....when i return ....car starts right up ...but when i accelerate it will not shift into the next gear and will die.....the only way i can save it from doing this is by shifting into neutral and revving the engine.....once it does get going it will not show these symptoms unless i turn it off and wait a few minutes......so again....never stalls when starting cold..only after it is warm....will start and idle fine...but if i accelerate it will go to about 25-30 k rpm and then lose power....only way to stop it from stalling is to shift into neutral and rev it pass those rpms....then it is fantastic for rest of the drive....never dies at lights etc
problem is worse in the summer than in the winter

other facts
gets between 22-28 mpg depending on season..i was hoping for better when i bought it
ive changed spark plugs
cleaned throttle body

ive tried to clean the iac valve but couldnt get it off

replaced air filter
no codes ..no check engine lights


any ideas from the pros out there?....im not very car savvy....thanks for any futre help w/ this drew

drewd,

I just solved your exact same problem in my gf's car after about two years, same as you. Been lurking the forum for a while but I just finally solved this issue a few weeks ago.

Turned out it was the upstream 02 sensor. I figured this out only after buying a new Actron live data scanner with graphing, and trading cars with her so I could drive it to work every day to see the issue. The first 1.5 years it was doing it so intermittently, last 6 months it started doing worse. Had it to my local mechanic who was stumped, because it was not doing it that day.

I did mostly the same things you did too:

-New AC delco plugs and wires

-New Dorman air intake tube with sensor assy, original was ripped wide open

-Took throttle body off car and IAC and TPS off, cleaned, lubed, reassembled with new TB gasket.

None of this work I did CHANGED OR HELPED THE HOT RESTART STALLING IN ANY WAY. THE NEW UPSTREAM 02 SENSOR SOLVED IT 100%. I'm going to write up a more detailed post about it because I think alot of 2004 aveo's have this problem.

Basically your upstream 02 sensor is old and not heating up and responding to the ECU's switching fuel trims. I caught this during an OBD-II scanner recording session. The car was already warm, and the ECU went closed loop. BUT the 02 sensor stayed flatlined HIGH at about 0.78V, which is a rich fuel condition. In response the ECU start commanding the short term fuel trim lower and lower, down to -20% to -25%. Then the car would either stall on its own, or the ECU would switch back to open loop. I would have to shut the car off manually in neutral while rolling, restart it to force it open loop again, then drive off. By the time I drove off the exhaust gas would heat up the 02 sensor and it would run fine rest of day as long as I didn't shut it off again. So a long drive to the beach was no problem, but a short drive to the gas station, or store involving many hot restarts would make it buck, stall, feel like the throttle cable was made of a rubber band.

NONE OF THIS STALLING OR SLOW 02 RESPONSE EVER GAVE ANY CODE OR CHECK ENGINE LIGHT OF ANY KIND. IN OVER TWO YEARS. EVEN WHEN THE PROBLEM GOT MUCH WORSE.

I believe the 2004 Aveo ECU firmware does not properly respond to a long 02 sensor response time. I have a feeling if I had gotten my ECU reflashed at the dealer, the check engine light would have come on. My gf bought this car new in 2003, so I know the history and it is the original firmware in the ECU as far has I know.

Hope this helps sorry for long post.

[drewd]

drewd,

I just solved your exact same problem in my gf's car after about two years, same as you. Been lurking the forum for a while but I just finally solved this issue a few weeks ago.

Turned out it was the upstream 02 sensor. I figured this out only after buying a new Actron live data scanner with graphing, and trading cars with her so I could drive it to work every day to see the issue. The first 1.5 years it was doing it so intermittently, last 6 months it started doing worse. Had it to my local mechanic who was stumped, because it was not doing it that day.

I did mostly the same things you did too:

-New AC delco plugs and wires

-New Dorman air intake tube with sensor assy, original was ripped wide open

-Took throttle body off car and IAC and TPS off, cleaned, lubed, reassembled with new TB gasket.

None of this work I did CHANGED OR HELPED THE HOT RESTART STALLING IN ANY WAY. THE NEW UPSTREAM 02 SENSOR SOLVED IT 100%. I'm going to write up a more detailed post about it because I think alot of 2004 aveo's have this problem.

Basically your upstream 02 sensor is old and not heating up and responding to the ECU's switching fuel trims. I caught this during an OBD-II scanner recording session. The car was already warm, and the ECU went closed loop. BUT the 02 sensor stayed flatlined HIGH at about 0.78V, which is a rich fuel condition. In response the ECU start commanding the short term fuel trim lower and lower, down to -20% to -25%. Then the car would either stall on its own, or the ECU would switch back to open loop. I would have to shut the car off manually in neutral while rolling, restart it to force it open loop again, then drive off. By the time I drove off the exhaust gas would heat up the 02 sensor and it would run fine rest of day as long as I didn't shut it off again. So a long drive to the beach was no problem, but a short drive to the gas station, or store involving many hot restarts would make it buck, stall, feel like the throttle cable was made of a rubber band.

NONE OF THIS STALLING OR SLOW 02 RESPONSE EVER GAVE ANY CODE OR CHECK ENGINE LIGHT OF ANY KIND. IN OVER TWO YEARS. EVEN WHEN THE PROBLEM GOT MUCH WORSE.

I believe the 2004 Aveo ECU firmware does not properly respond to a long 02 sensor response time. I have a feeling if I had gotten my ECU reflashed at the dealer, the check engine light would have come on. My gf bought this car new in 2003, so I know the history and it is the original firmware in the ECU as far has I know.

Hope this helps sorry for long post.

wow that is great news...do you have info on what upstream 02 sensor you used? make and number? thanks drewd

[enflux75]

hey drewd,

sorry haven't logged on the forum for a while.

yes i used AC Delco part# 213-4272, it is the real OEM replacement part as far as i've been able to research. I got it online (not from a dealer)

it was very easy to change underhood, I just had to take the exhaust manifold heat shield loose so I could get better access to it with an open ended wrench, luckily the original sensor seemed to have anti-seize on the threads from the factory. I bought a special O2 sensor crowfoot wrench with an opening for the wire, but I ended up not even having to use it

[drewd]

finally took the plunge and changed out my upstream o2 sensor...and voila ....problem fixed
thanks to all for their input drew