sp52075

can you reprogram you computer driven vehicle by driving it a certain way? I read an article a few years ago about how you car can pick up the way you drive and more or less set itself to run more efficiently toward your driving style. so if You stomp on it alot it tunes for performance if you baby it it sets for efficiency. I have an 07 with the 2.4 auto and the last month i have been getting 26-27.5MPG with about 70% freeway driving cruising about 65-70 with some stop and go traffic and of course because it was new I would get jollies bye driving like I stole it enjoying the power from such a small engine you know keeping it floored for a while. then the last few weeks I have been driving like a 300 year old blind grandma keeping the speed with in 5 MPH of the limit and no fast starts just crusing. same route and mix of freeway and city trying to see if the MPG would go up much they did my last tank I was at 29.5 MPG (yay!! me) but then this morning on my way to work I was running a little late and needed to pass a few cars on the back roads and it seemed to take forever I put my foot down and just sort of eased by them. Not wiz by like before and I didn't feel the pull it used to have. I have also noticed this in my wifes suburban also. And I always get gas at the same station its been 87 octane. Is this possible or just in my head because I read it somewhere

a76marine

My old Dodge Magnum did this but I have not heard yet about the HHR doing it.

Others might be more helpful tho...

JoeR

The ECM calibration only has two areas where there is any "learning" taking place.

There are two spark advance tables, high and low octane. Depending upon how much KR (knock retard) is detected, the computer's algorithms will compute the Knock Learn Factor, which will basically average up or down between the two table values. IOW, if knock is detected advance will average down towards the low octane table. If none is detected over time, it will average up. The octane level used will have a large effect on this. Also running it hard on low octane will more likely experience knock and lower timing. This is why GM says that 91 octane is "recommended", but that you can use lower octane.

The only other parameter that "learns" is the Fuel Trims. There are hard numbers coded into the calibration, but variances in temp, air pressure, etc. are adjusted via the Fuel Trims. The O2 sensor constantly monitors any variance from the desired 14.7 stoic AFR and computes the numbers to factor against the hard coded tables to keep everything on target. If anything gets out of bounds (~ 20%), a CEL will get triggered.

Simple, huh?

HHR4JK

FYI........Mine 2.4 has never knocked on 87...... the dealer put 87 in when i first bought it..... i have tried the 91 recently to see if the mileage would be better but no different...... nor is the power...... i still got great get up and go.....
so i guess the computor has done its job.? Dont matter it runs great.......

ChevyMgr

Short answer is no. See JoeR post #3 for the long answer.

Driving differently will not reprogram the computer, but fuel octane, fuel quality (ie amount of alcohol), engine temperature and other variables mentioned by JoeR will.

You may have been at the threshold of speed and RPMs that didn't allow for the downshift to occur.