will not idle after it got cold outside

whynot · Post by **whynot** » Wed Feb 05, 2014 11:21 pm

So I pulled and cleaned the throttle body this weekend, and everything ran fine. Today, the temps fell to the teens (cold for here and colder than it has been) and it will not idle. After 20-30 min it idles fine.
I unplugged the iac, and nothing changed. but I did this with the car running.
How do I test this? and find the issue?

Thanks
Doug

NickKo · Post by **NickKo** » Wed Feb 05, 2014 11:53 pm

Any codes ??

If I had to *guess*, I suspect there may be issues with the CTS (Coolant Temp Sensor) circuit.

- Nick

whynot · Post by **whynot** » Thu Feb 06, 2014 1:16 am

no codes at all.

NickKo · Post by **NickKo** » Thu Feb 06, 2014 7:22 am

Try pulling the codes with a scanner, if you can - It's possible that a code may have been set, without triggering a CEL.

This happened on my 1st gen Neon. (Which may be different, but anyways....)
I had the CTS go bad, but it did not trigger the CEL... I had to use a scanner, to pull the code.

Symptoms: The car would not start when it was 'cold'.
It would have no problems re-starting if the engine was warmed up, however.
Another weird side-effect of the bad CTS, is that the radiator fan would kick on immediately.... Even if the engine was 'cold'.

- Nick

whynot · Post by **whynot** » Thu Feb 06, 2014 9:34 am

I have not paid attention to if the fans kick on at startup. I will get a scanner on it and see if there is anything. I was just doing the key to display the codes in the dash.
The gauge works is that from the same sensor?

Post by **occasional demons** » Thu Feb 06, 2014 10:50 am

If this is the 2003 you have listed, and unplugging the IAC does not change it, either you have a vacuum leak somewhere, or the IAC is sticking until it gets warm.

It is basically a solenoid, that is returned shut by a spring. Disconnecting the power should let it snap closed. You should also get a CEL/codes when disconnecting it while the key is on, or running.

If you can put your finger over the IAC inlet while it is idling fast, and it idles down, or stalls, you then know there is a problem with the IAC, or possibly the circuit/PCM if there are no codes from disconnecting it.

If unplugging it did change things, then like Nick said, a coolant temp sensor may be an issue.

On 2gn's yes the gauge and the ECT are on the same sensor. The PCM just forwards the info to the cluster. 1gn's are two separate circuits.

whynot · Post by **whynot** » Fri Feb 07, 2014 3:58 pm

so the hose that plugs into the IAC comes from the back of the engine compartment, and drops under the car. I assume it is running to the tank?
Also the one from the valve cover goes to the small filter in the air box. I had both of these off, did I swap them?
No codes yet, it was a long trip home last night. I did pull the IAC again this morning, and have cleaned it. Letting it dry inside and see what happens then. I do not see anything loose. Just maybe I swapped the hoses, but I do not think so.

whynot · Post by **whynot** » Fri Feb 07, 2014 7:01 pm

Checked the car, and there are no codes with my scanner

Post by **occasional demons** » Fri Feb 07, 2014 8:43 pm

That hose goes to the purge flow solenoid under the brake booster. The IAC gets it's air from the hole inside the TB before the throttle plate. That is where you should put your finger when it is running to see if it idles down. If you take the air filter off, while the IAC is off, you will see what I mean.

whynot · Post by **whynot** » Sat Feb 08, 2014 4:03 pm

ok, I will check that, maybe I got something in there when cleaning it? I did not see anything down inside after pulling the IAC, but the filter was still on.

MichNeon · Post by **MichNeon** » Thu Feb 27, 2014 10:48 pm

NickKo wrote:Try pulling the codes with a scanner, if you can - It's possible that a code may have been set, without triggering a CEL.

This happened on my 1st gen Neon. (Which may be different, but anyways....)
I had the CTS go bad, but it did not trigger the CEL... I had to use a scanner, to pull the code.

Symptoms: The car would not start when it was 'cold'.
It would have no problems re-starting if the engine was warmed up, however.
Another weird side-effect of the bad CTS, is that the radiator fan would kick on immediately.... Even if the engine was 'cold'.

That is a "limp - in" feature. If the pcm does not get a reliable reading from the cts, it does'nt know when to turn the fans on/off. There are several sensors that, when they don't respond or stop working, the pcm will put the car into limp - in mode. The limp - in mode is one program that is the same between theSBEC, FCC, and the K car/L body cars. I would'nt be surprised if the NGC pcm has the same program in it.

- Nick

whynot · Post by **whynot** » Sat Mar 01, 2014 5:35 pm

ok, It is better because it warmed up a little, But it still happens early in the morning.
I am going to the JY monday for my 97
I will grab an IAc from a 2001 and a coolant sensor. Where is the coolant sensor at?
Thanks

NickKo · Post by **NickKo** » Sat Mar 01, 2014 8:56 pm

whynot wrote: I am going to the JY monday for my 97
I will grab an IAc from a 2001 and a coolant sensor. Where is the coolant sensor at?
Thanks

It's on the driver's side of the cylinder head.

- Nick

MichNeon · Post by **MichNeon** » Sun Mar 02, 2014 8:50 pm

NickKo wrote:
whynot wrote: I am going to the JY monday for my 97
I will grab an IAc from a 2001 and a coolant sensor. Where is the coolant sensor at?
Thanks
It's on the driver's side of the cylinder head.

- Nick

Actually, driver's end of the cylinder head, next to the cam sensor.

Post by **occasional demons** » Sun Mar 02, 2014 11:20 pm

My 2001 no longer stays running when cold either, but I just attribute that to poor compression. Using the throttle to keep it running for the first 10 to 20 seconds will usually do it tho, and it is fine after that. But no throttle, and it will just fire and stall.

At this point, I consider each day it still runs as a gift.

Any IAC or coolant sensor from 2001 to 2005 should work, as long as the IAC isn't from an SRT. A 2000 coolant sensor would probably work too.