problem with "cold" starting

Hello all...I am new here. I found this site when experiencing alternator problems about two months ago.
Here goes... 2008 Aveo...when cold, particularly in the morning, the car behaves strange on the initial start up. Example... Engine fires, and after releasing the key from the start position, engine runs rough for about 1-2 seconds then dies. Try again...same thing. Third (sometimes the fourth) try the engine will stay running, but run rough for about the first 5-7 seconds, then "smooth out" to normal. There is not a check engine light, so I am not sure there will be any codes set on the ECM. Strange thing is, this just suddenly started happening about 7-10 days ago, and it only does it when cold. I am wondering if there might be a bad sensor and the ECM "thinks" the engine is already warmed up. Once warm, the engine runs and drives fine. No drivability issues that I am aware of. Any suggestions ?

it could be the temp sensor, i'm not sure if that would through a code or not, i think it should, but you might still be in the parameters.. but it could really be a few things. This is a tough one to diagnose online..

Yeah, I know. And it will be tougher to try and diagnose as the weather warms up. We had a few days in the mid 70's here already, and the car seemed ok on those days. I notice that it's worse the colder it is. That's why I think it might be a bogus temperature sensor. If I don't get it figured out now, it may have to wait until the fall when we have those crisp early autumn mornings... Anybody know what/how that inlet air temperature sensor is supposed to work ? I did have to remove the connector when removing the air inlet tube a couple months ago when replacing the alternator. If I knew the pin-out or color code of the wiring on that connector, concievably I could look at the voltage on those pins (when cold) to see if it is in the normal expected range. I am relatively new to these ECM / computer controlled cars. I am old school, Holley carburetor, rear wheel drive, and lots of cubic inches "old", so try to be patient and bear with me as I learn...thanks

its the coolant sensor that sets the cold start, not the intake air temp..

Quote:

---

Originally Posted by petrified.rabbit

its the coolant sensor that sets the cold start, not the intake air temp..

---

That is correct. A coolant sensor that reports higher than normal temperature will affect cold starting and warm up.

Coolant sensor...gotcha. Now, where's it at, and how do I tell if it's reporting the correct voltage for the ambient temperature ?
I am assuming that there's some kind of "look up chart" where there should be say...3 volts at 30 degrees, 5 volts at 50 degrees, 10 volts at....blah blah blah. You get what I mean. I would hope I could read it directly across a couple of pins on the sensor with a voltmeter. Or is it more complicated than that ?

i think its just an open/closed. not 100% sure, but in the wiring diagram its just 2 wires, no reference.

Quote:

---

Originally Posted by petrified.rabbit

i think its just an open/closed. not 100% sure, but in the wiring diagram its just 2 wires, no reference.

---

Nope. Straight from the manual:

The coolant temperature sensor (CTS) uses a thermistor to control the signal voltage to the engine control module (ECM) and controls the instrument panel temperature indicator.

Here is the chart of both the IAT and ECT sensors.

thats good to know. i guess i need to read more of the manual.

The reason I know is I couldn't start the car one morning and the reason was the coolant sensor.

#24 on the next picture is where the sensor is:

You guys are awesome. This is really good info to have. Now, I am thinking that if it is a bogus resistance reading from the coolant temperature sensor, wouldn't it also affect "warm up" ? In other words, why wouldn't it run really bad until everything is warmed up...As it is right now, once the engine fires and runs for more than 5-7 seconds, it smooths out and then seems to run normally. Or is the ECM only looking at the CTS to tell the injectors how much fuel is needed to start the car, and that's it. Trying to understand how it's supposed to work. I will see if I can locate the CTS and read the resistance with an Ohmmeter, and record the values...let you know what I find out. Thanks again for your replies. I really appreciate everyones help !

that is getting into mapping of the ecu. And "circuits" it uses at different points.

not sure I understand what you mean by mapping of the ecu & "circuits" it uses at different points. Can you clarify ?
I can't seem to get it out of my head that a bad coolant sensor reading that affects starting when cold would also affect
engine running conditions until "warmed up"...but like I said earlier, I am still learning this computer controlled stuff.
There might be a perfectly good explanation that I am just unaware of because of my lack of familiarity with the systems in play.

The coolant temperature sensor (CTS) could be the problem with cold start problems. It was on my 2005 Aveo LT. Had terrible time starting when cold. Actually hard to start after sitting 8 hours or more in 70+ degree weather. I tried several things before I found the actual problem. A defective sensor does not set a code. So for me it was try this and then something else.

As it turns out the CTS was the least expensive part to buy but the hardest part to get access to on my Aveo. Forget about testing it. If you get to it, replace it. I could only access it from below the car when it was jacked up. The CTS screws into the back side of the engine block below the intake manifold, between the engine and the firewall. There is an engine brace which is in the way and must be removed. It has 4 bolts in it. The bottom two bolts are #14 metric the top two are #13 metric. The top ones required me to use a short extension to remove. Once the bracket is moved to the left side of the car you can access the CTS. There is a clip on the two wire connector which must be released. This is tricky using only one hand. Once the wire is removed you can access the CTS.

Remove the pressure cap on the water inlet tank. When you remove the CTS water/anti freeze will come out of the hole. You may want to drain the coolant first. I did not. You will need a 3/4 inch SAE deep-well socket to remove/reinstall the CTS. It comes out easily once loosened. Good Luck, sorry no pictures were taken.

Please help me to solve this problem i am also facing such issue in morning

Just my 2 Cents, I am currently having this same problem, I even had my mechianic looked at it and he didn't seem to mind this obvious problem on the Air Cleaner Intake Hose or ACIH (Picture Attached), The inside was full of grease, dirt and other stuff that went into the Main Throttle Idle Actuator (MTIA) and clogged the holes in it with the same black grease and dirt...sight.

I'll buy the new ACIH have my mechanic clean up all this parts, replace the air filter and I'll post back after all this is done. And maybe get a new mechanic afterwards.

Hope it helps!

PD
I was ready with my soap and water just to check for punctures or leeks and found this! :D

Quote:

---

Originally Posted by ramquez31

Just my 2 Cents, I am currently having this same problem, I even had my mechianic looked at it and he didn't seem to mind this obvious problem on the Air Cleaner Intake Hose or ACIH (Picture Attached), The inside was full of grease, dirt and other stuff that went into the Main Throttle Idle Actuator (MTIA) and clogged the holes in it with the same black grease and dirt...sight.

I'll buy the new ACIH have my mechanic clean up all this parts, replace the air filter and I'll post back after all this is done. And maybe get a new mechanic afterwards.

Hope it helps!

PD
I was ready with my soap and water just to check for punctures or leeks and found this! :D

---

When mine did that I thought I had a bad muffler.. Now I've got the cold start issue when it is 35 or lower, sounds like I'll buy a sensor then spend some time under the car, at any rate at least I can fill my gas tank without it taking 30 minutes now that I replaced the EVP canister and valve.

Quote:

---

Originally Posted by waynek20047

The coolant temperature sensor (CTS) could be the problem with cold start problems. It was on my 2005 Aveo LT. Had terrible time starting when cold. Actually hard to start after sitting 8 hours or more in 70+ degree weather. I tried several things before I found the actual problem. A defective sensor does not set a code. So for me it was try this and then something else.

As it turns out the CTS was the least expensive part to buy but the hardest part to get access to on my Aveo. Forget about testing it. If you get to it, replace it. I could only access it from below the car when it was jacked up. The CTS screws into the back side of the engine block below the intake manifold, between the engine and the firewall. There is an engine brace which is in the way and must be removed. It has 4 bolts in it. The bottom two bolts are #14 metric the top two are #13 metric. The top ones required me to use a short extension to remove. Once the bracket is moved to the left side of the car you can access the CTS. There is a clip on the two wire connector which must be released. This is tricky using only one hand. Once the wire is removed you can access the CTS.

Remove the pressure cap on the water inlet tank. When you remove the CTS water/anti freeze will come out of the hole. You may want to drain the coolant first. I did not. You will need a 3/4 inch SAE deep-well socket to remove/reinstall the CTS. It comes out easily once loosened. Good Luck, sorry no pictures were taken.

---

I had purchased a Vapor Canister Purge Solenoid Valve along with a vent valve and Vapor canister but had not installed it due to its location, right in front of the brace that blocks access to the CTS. If anyone knows of any means to remove the tube 'clips' without breaking them please speak up! I think if the vehicle was on a lift it would not be so bad but laying under the vehicle with only one handed access at 27F with a drop light is not fun at 73. When I finally pulled the CTS out the antifreeze started running out, I got the new one installed but not before the antifreeze had hit the drop light which became a drop dark. After everything was reassembled I still had a few seconds of blah when II started it, I warmed the car up and topped the antifreeze off. 5 hours later at 29F I just tried to start it, works great again.

The Vapor canister, vent valve and Vapor Canister Purge Solenoid Valve solved my having to spend 15 minutes hand filling at a trickle the gas tank, been doing that for three years before it dawned on me there might be something wrong.... The canister was full of dirt.