Engine-off-coasting (EOC) with GM Ecotec cars
 

Something I noticed with my new-to-me 2006 HHR. It has the 2.4L Ecotec engine and if I use EOC before the engine is warmed up, the temp gauge can go dead. This issue is well understood. When the computer detects the car in motion and the temperature is too low for extended periods, it turns off the coolant temp sensor input. (Not sure why, I would think a dash light would be a better warning)

For non-hypermilers over on the HHR forums, this is an indicator that the thermostat is stuck in the open position and the fix is to get a new thermostat. In fact, how I found out about it was that it happened once to me and I changed the thermostat. Then it happened to me again and I knew it couldn't be the thermostat again, so I figured it out. It was because I was EOC-ing and it happened while traffic was moving slowly down a long grade, so I just coasted (engine off) for a good 10 minutes while the car wasn't up to temp yet. The conditions would look the same as a stuck thermostat to the car's computer.

Anyway, the purpose of this is to let others with GM Ecotec 2.2L/2.4L engines and manual transmissions who can use EOC (e.g. Chevy Cobalt, HHR; Saturn Ion, L200; Pontiac G3, Grand Am) that if this happens, don't spend money trying to fix it. Just drive it a little ways to get the temp up and it should fix itself after a few minutes.

I have the 2.2 ecotech engine. I want to add a kill switch most likely to the injectors but have no idea how to do this. Do you know anyone whose done it?

I noticed when I turn off the vehicle I have to start it again and I do not want to wear down the starter. When off the vehicle does not record my miles therefore it will show as worse mileage on my gas logs.

I have been searching for more complex information on my engine but do not know where to look. Can anyone point me in the right direction?

Typically instead of using the starter unless at a dead stop people bump start there cars to start em while coasting. If done properly its suppose to add no more stress on the clutch than normal shifting.

If you key off the motor simply turn the key back to the on position and it will be closer to accurate miles.

i don't know of any1 whose done a kill switch to an ecotech, but im pretty sure some1 had done it this way i would research it more, but all u should have to do is unplug the injector fuse run a wire from the 1 side of that fuses box then connect to 1 side of the fuse, then connect another wire to the other side of the fuse and run it to a switch inside the car for you to turn off/on then run the wire from the switch back to the fuse box to the other side.

Even with key to "on" position, the odometer seems to be off. The key has to be in the "running" position. I dislike the way they did this.

I am also wondering if anything bad would happen by just turning off the injectors lets say 1/2 way in the middle of injecting fuel. Would that lean out that cylinder and possibly cause detonation, or would the injector finish pumping that fuel before it shuts off?

It seems my car does have some sort of EOC feature because sometimes when downshifting to slow down, scanguage shows 9999 indicating fuel injector shut off. I wonder if there is a way to tap into that system and shut it down when I want it off.

Me too. Also, I noticed when EOC-ing, the avg. fuel economy display (2006 doesn't have instantaneous fuel economy reading) doesn't update till the engine is running again. I don't know why.

Yes, that can cause all sorts of problems. Lean condition, high NOx emissions, confused computer.

This is true on almost all (if not all) modern cars. It's called DFCO (Deceleration Fuel Cut Off). When the wheels are spinning the engine (the opposite of the usual scenario), the injectors cut off to save fuel. I have a really long hill to go down on my way home and in the summer, I turn on the A/C down that hill because it's free. The hill's potential energy turns the engine and the A/C compressor.

is the key in the on position or acc? different cars so there would be different results but when in the on position its the same as the running position.

and yes you seem to have DFCO i wish i had it

Your '99 Escort and '02 Grand Am don't have DFCO?

nope

How do you know?

with dfco my ultragauge should go to 999 rite? The highest i have ever gotten it is about 110mpg coasting in gear