Intermittent Stalling Problem

[Oil Changer]

Had a detailed post written that got lost in Internet cyberspace.

Cliff note version:

Car stalls at idle when warm. No CEL or codes. Sometimes starts right back up, sometimes very difficult to re-start. Visual inspection showed nothing out of the ordinary.

Would like to know if anyone else has had this problem and what fixed it; point me to something I missed while searching this forum, and/or offer ideas.

2008 Aveo 5 Special Value
E-Tec II 1.6L
5 speed manual
100% bone stock.
Very well maintained
59,100 miles

[petrified.rabbit]

there are a few things this could be are you able to test anything or are you going to throw parts at it?

[Oil Changer]

there are a few things this could be are you able to test anything or are you going to throw parts at it?

I am able to do some minor testing. I'll throw parts at it if the price is right. I'm open to all ideas right now.

[wuwei37405]

I would guess (and I do mean guess) that it is the ignition coil. They are not cheap by my standards, costing from $65 to $95. So, I am asking, "Do you want to spend that kind of money on a hunch?" Also, if the wires and plugs are old, you might want to replace them at the same time. Good luck. If you try it, and it doesn't work, I apologize in advance.

[Oil Changer]

Still here. Welcome any responses. Car still stalling at idle when warm only. Plugs/wires changed about two months ago with Bosch Iridium/BWS wires.

Smell coolant but see no leaks/wet spots/drips. Level still normal to high.

The only thing that has changed is the weather; 30 degrees F or less typical average now.

Runs like a champ when at any RPM other than idle.

Rough idle (but not extreme) and idle dips real low when trying to stop for light/sign/traffic. Lights on/high heat (eg. high electrical demands) does not seem to matter.

[petrified.rabbit]

it sounds like the car is not going into "high idle" for the cold weather, there is a temp sensor for that. The problem is it happens when it is warm, not on initial start up? So that could be the AIT sensor, or even just a leak in the intake pipe nearby.

the issue really is an idle issue, so vacuum leaks, idle switch sensors, tps, or a dirty throttle body could be suspect.

[wuwei37405]

You smell coolant. Check the spark plugs. If any of them have coolant on them, you may have a head gasket leak. Again, good luck.

[Oil Changer]

it sounds like the car is not going into "high idle" for the cold weather, there is a temp sensor for that. The problem is it happens when it is warm, not on initial start up? So that could be the AIT sensor, or even just a leak in the intake pipe nearby.

the issue really is an idle issue, so vacuum leaks, idle switch sensors, tps, or a dirty throttle body could be suspect.

Fires right up every morning and after work when it's been sitting all day. I'll let it warm up for at least 15 minutes every morning and it has yet to stall. To repeat, the only time it stalls is at idle after the engine is throughly warm.

Example: Leave work, start car, idle for a minute, drive 3 miles surface streets to express way ( no problems), drive 10 miles express way and exit, drive surface streets, stalls at lights/sitting in traffic. Not every time. Sometimes it starts to shudder and I can save it by bringing it off idle, sometimes stalls with no warning. When trying to re-start, it will either fire up with a little longer than normal crank or on a couple of occasions, I had to push the car off to the side and wait a minute before trying to re-start, which it does; sometimes immediately, sometimes with a little effort.

When at speed, the car runs like a clock. No loss of power or fuel economy. No CEL or codes.

[Oil Changer]

You smell coolant. Check the spark plugs. If any of them have coolant on them, you may have a head gasket leak. Again, good luck.

The coolant smell is new and worrisome. I put carboard under the car. No leakes of any kind. Visual inspection showed no obvious leaks. I marked the reservoir hot and cold, no change/still topped off. Nothing unusual coming out the tail pipe.

I will look for bubbles while running. I can not work on the car until Sunday. My neighbor has a punp where I can put the coolant system under pressure and look for leaks. I'll pull the plugs and look first.

[Oil Changer]

Thanks for the ideas thus far. I will work on the car tomorrow and keep you posted.

The only thing else (and I hesitate to bring it up) is a few days before this started, I had the car at a well-known national tire chain store to have my winter wheels/tires put on. I had an appointment so I was able to wait/watch. It looks like they did a fine job. I had no problems last year with the wheel/tire swap but this stalling did start happening a few days after the install.

Could something have got damaged while on the lift?