My car has always run horrible during the winter. When it warms up it runs perfect. I am getting no SES and it has done this with two different engines. I don't have any way to scan it right now so I can't help there. Could an IAC do this or am I overlooking something. I have no vacuum leaks and the car runs perfect after warm and also runs perfect in warm weather.

 

don't know if helps but i used to have problems with my car when cold... was a bad MAF....
i missed the year of your car, i don't know if you have a MAF... sorry

 

I tried another MAS and it was the same. I am not sure what all sensors are affected by the cold. I have installed a new knock sensor, cts, O2 sensor(I broke one), coil, opti, MAS, new plugs and wires when I put the new engine in two weeks ago. It has to be something to do with a sensor that is affected by temp and controls idle in open loop. As soon as it goes into closed loop it runs perfect.

 

If it runs perfect in closed loop, then that pretty much shows that all of the sensors are working properly. Could quite possibly be in the tuning.

 

I was hoping it wasn't going to be anything like that. Could cold air be causing my IAC to stick? I have ram air if that matters. The last time I had this problem was last winter.

 

Agreed, it sounds like the PCM tune might be off. In open loop it uses the PCM's tables exclusively for determining proper AFR. After it warms up and switches to closed loop it uses the O2 sensors as a feedback mechanism for determining proper AFR, and can compensate for incorrect tables.

If you have your PCM tune in .BIN format, I'd be happy to take a look and see if anything looks abnormal.

 

FYI, the IAC motor only helps with idle control. It's not going to make the car run bad when it's cold and good when it's hot. It's the device that keeps your car from dying when you make a quick stop, turn on the AC, etc.

 

he's absolutely right...I believe the open loop runs until coolant temp exceeds 150 degree's F, along with a few other parameters, if those are never met then it will run in open loop. And if your open loop code is meant for a stock engine and yours is not, or somehow they are off, it will explain why your car runs like crap.

 

I had my PCM reflashed by Ion. I gave him all my cam specs and head info. He flashed it last time as well. The reason I was asking about the IAC is because my car nearly dies and sometimes does when I turn on A/C. I will try and clean it this weekend.

 

i seem to have sort of the same problem, but i guess a little worse. i seem to lose a lot of power in the winter, even to the point where it is stalling. a ton.

heres my post http://web.camaross.com/forums/showthread.php?t=488541

 

What if the throttle blades were adjusted too far open? The IAC controls how much air is allowed into the intake with the throttle closed. I would suspect in the winter time, less air is needed to achieve proper idle mixture. If the IAC is bottoming out and too much air is getting past the IAC needle, the PCM would no longer be able to control idle.

 

My TB still has the factory plug in it for adjustment. It idles perfect when it warms up. It pops and bucks when cold. It acts like a carbed car. I am going to clean the IAC if for no other reason than it is probably overdue. I don't have any missing or stumbling once the engine is warm. The problem does seem worse with the new engine than with the old one. The IAC and TPS are original and as far as I know have never been removed. The throttle body is off of a 94.

 

If you have access to a data logger/scanner, it'd be interesting to know what your IAC step count is when the engine isn't running properly.

 

No, but I wish I did. There is an article on cleaning and resetting the IAC on Shoebox's website. I think I am going to try that tomorrow. The last time I scanned the car was to try and figure out why it was dieing with the A/C on. The PCM was seeing an A/C request signal, but it wasn't increasing idle.

 

The PCM will see that the A/C is on, but it won't automatically increase idle speed. When the engine bogs down, the PCM sees that and opens the IAC motor to allow more air to flow, raising the idle. You could borrow someone's IAC and see if it helps. You do need a way to see the sensors, so that you can get the counts where they need to be. Either way, your 'poor running' problem should have nothing to do with the IAC. I agree that a log would be the best way to actually see what the car is doing and make sure all the sensors are acting properly. It's rare to hear of people's cars running bad in open loop and good in closed loop.