i have 2 questions

1. i know the ECU's are made to 'learn' your driving habits. I've been driving pretty spiritedly for the last 2 weeks. Ive noticed that when I go back to normal driving, I've been getting worse gas mileage (20-22 mpg ). Should I unplug my battery, and let the ECU reset, to re-learn better driving?

2. I know on some cars, the ECU runs in closed loop for the first 90 seconds after the car is started up. Is this true for the cobalts? I let the coolant warm up to 160-180*F before getting on it, but thats not always after 90 seconds. I can imagine this would cause bad gas mileage as well, should I granda drive for the first 90 seconds?


Thanks in advance

 

Closed loop is determined by engine temperature not time.

If you want better economy, let it idle for 30 seconds after startup then drive. Go easy until it's fully warmed up. Driving the engine makes it warm up faster and the faster you get to closed loop, the less fuel wasted.

 

actually it is determined by time, coolant temp, and 02 sensor temp

 

Actually it depends on 3 things in accordance to each other coolant temp, time and O2 sensor temp.And actually you will get better gas mileage if you let it warm up cause in open loop your car runs on a preset amount of fuel which is really really really rich so you would be using alot of gas if you just jump in and drive plus thats bad for you engine to not let it warm up. The terms form closed loop is "estimate its been along time since LTI" engine has to run for 90 seconds, coolant has to reach 150 degrees and 02 sensor has to reach 300 degrees ithink i can look it up to be sure.

 

Are you seriously trying to tell me that letting the engine idle until it's fully warmed up is good in any way for your car?

The colder the engine is, the more fuel the PCM will dump in to try to get it warm. The longer it idles, the longer it takes to get warm.

There are umpteen million articles on google that will explain why idling is bad for your engine. From excessive deposits on the plugs to condensation in the crankcase. There is no reason to let a modern engine idle for any longer than 30-60 seconds to get the oil circulated and then drive moderately till operating temperature is reached. That is unless you like wasting money.

 

good information guys
so how long should i wait until driving aggressively?
should i just keep an eye on the coolant temp?

 

Watch the coolant temperature. Once it hits the 180-190 range for a bit, you can drive it hard.

 

you have no idea what your talking about noob

 

ge's not talking about idling for 20 or 30 minutes you have to let your engine warm up otherwise like someone said it will run way to rich to prevent an engine disaster for u being too impatient to let your car warm up. BTW A cooler engine is good but not too cold there is a certain range of acceptance like when I dyno I put it up and let it cool down then after it is done cooling down I turn it on and run until coolant is about 150 that way you make the best use of a cooler engine within normal operating temps that equates to maybe 2 or 3 more hp but hey anyway you can get it.

 

You speak the truth. Noob.

 

I don't think the ECU learns drivng habbits. Maybe I am wrong. If you drive real nice you get good gas mileage and if you floor it--well it goes down. Isn't this like every other car?

Ceratin automatics do (no not rh 4 speed auto in the Cobalt) ECU can learn from mods I think.

 

You're right Av, it doenst learn your driving habits-really. What it does is trim the fuel delivery in an attempt to obtain 14.7:1 (stoiciometric) as much as possible during steady road loads. As you drive you will be in one of 16 primary trim cells (0-15) that is dependant on engine RPM and load. So if you drive it "nice" the closed loop system will "trim" only the lower cells (and stores/rememebers those trim levels (in each cell) that's required to acheive stoich ratios)
If you drive it like you stole it, it will trim the higher # cells more quickly due to the higher engine speed and loads.

So it's true that a "granny" might never trim cells 11-15 as she doesnt ever drive there!
So in THAT sense only- "it learns your driving habits" (typical service advisor statement)
HTH
WopOnTour

 

"Noob?" LOL.

Almost 7 years in the auto repair industry doesn't make me a noob, son. I have yet to find a tech anywhere online or in person that agrees with your theories.

You are the one that shouldn't be giving advice when you don't know what the hell you are talking about.

 

ive been in the indusdtry for seven years also but if you really have been in for seven years then you sghould know that means absdolutly dick to another mechanic ill just agree to disagree and dont call me son i aint no black man or your kid.

 

I decided to call you son because you were the one who resorted to name calling with the "noob" comment which was quite childish. Just because someone has a different opinion than you isn't a reason for that type of nonsense.

I will agree to disagree though.

I will invite anyone else who wants information on the subject to do google search using the terms "warming up a car" and then use that information to make their own judgement.

 

back on topic guys