Quick poor MPG test on 100k-ish cars

dcmfx · 01-08-2011, 07:28 PM

For those of you like me out there, good shape car getting poor mpg with no reason (already replaced EGR and cleaned my injectors and replaced my plugs and O2 sensor), please do this test and report back.

Pull the 12v battery.
Wait a couple minutes (go in and get a drink).
Reconnect the 12v battery.
Drive a few miles to get the IMA battery fully sensed.
Drive a drive you know and can feel the difference on.

Is it better, smoother, higher MPG, easier lean-burn?

Drive for a couple days.

Is it back to not so good?

Thanks
Dan

02insight · 01-11-2011, 09:39 PM

on my car I have cleaned EGR, cleaned injectors, replaced Spark Plugs. Mine also gets better MPG after a reset, but it doesn't really become that bad.

My02Insight · 02-03-2011, 10:39 PM

On My CVT i cant get better than 45mpg...I read these stories of folks getting 60-70 mpg on Non Modified INsights.....You must live in like Tennessee Or somewhere really flat....How can i get better MPG...ive already cleaned my injectors and changed my sparks...I do have a large 2mile hill to work everyday and go down the hill back from work...Going up the hill kills my MPG>

**Hybrid-Battery-Repair** · 02-04-2011, 09:16 AM

Quote:

Originally Posted by My02Insight

On My CVT i cant get better than 45mpg...I read these stories of folks getting 60-70 mpg on Non Modified INsights.....You must live in like Tennessee Or somewhere really flat....How can i get better MPG...ive already cleaned my injectors and changed my sparks...I do have a large 2mile hill to work everyday and go down the hill back from work...Going up the hill kills my MPG>

Try to drive so that your RPM stays below 2000 and you should be able to break 50 easily. I took a CVT owner on a test drive in his car and he was shocked when I pulled 62 on local hilly roads. The trick is to not gun it up the hills and to let it coast down them (using no fuel).

Proper tire inflation helps too.

randerson0248 · 02-04-2011, 09:48 AM

I have forced a relearn several times by disconnecting the battery ground cable. This was whenever I was doing work on the car that I wanted 12v power to be disconnected.

There was no change the things you mention; smoothness, MPG, ect.

**Hybrid-Battery-Repair** · 02-06-2011, 10:38 AM

Quote:

Originally Posted by randerson0248

I have forced a relearn several times by disconnecting the battery ground cable. This was whenever I was doing work on the car that I wanted 12v power to be disconnected.

There was no change the things you mention; smoothness, MPG, ect.

A relearn will only help MPG performance if the battery is really bad and then only for a short time.

3-Wheeler · 02-07-2011, 01:12 PM

Quote:

Originally Posted by Hybrid-Battery-Repair

A relearn will only help MPG performance if the battery is really bad and then only for a short time.

My experience the same as Ron's above.

I usually am forced to do a relearn when I purposely run the battery down on the way home from work while using MIMA-CL.

Overnight I use the Dabrowski trickle charger to top off the battery again.

The relearn is automatic after first starting the car in the morning on the way to work. It lasts about one minute and hurts the mileage during that time, but then resumes to normal after the relearn.

Jim.

randerson0248 · 02-08-2011, 09:42 AM

I'm not sure, but I think the OP is thinking the relearn is related to the ECU controlling the gas engine operation. Anyway, that is what I thought and what I meant in my comment.

jonnyvtec · 02-08-2011, 01:33 PM

Yes the ECU reset will reset the long term fuel trims that the car develops based on the short term fuel trim corrections it has to make.

The is typical on most cars based on trims to maintain stoich in cruise as it swings between the voltage threshold for rich and lean of a narrowband oxygen sensor (lambda), however in theory the Insight should be less sensitive to this as it has a real time Air Fuel meter in terms of a wideband lamdba sensor to moniter the actual air fuel.

02insight · 02-16-2011, 06:10 PM

I have read in the service manual that the 2nd O2 sensor control the fuel trims, and the 3rd is just to monitor the 2nd NOX cat.

So I disconnected both 2nd and 3rd O2 sensors on my car, reset the ECU and have been driving it with the CEL for the O2 sensors on. So far It feels like I have been getting slightly better MPG. Sort of how it feels after a fresh ecu reset, but since the O2 sensors are not available to the ECU to develop the fuel trims, it seems to be driving good, so far.

Try what I did, and see if it helps.