[Iceberg]

This is a long shot, but has anyone ever experienced a very sudden drop in MPG? I have a '01 CVT, and recently went from a usual 47 MPG (its hilly where I'm at), down to a consistant 35 MPG. I was getting 55 MPG before I moved to a hillier part of town, so the drop is really shocking.

I saw this sharp drop immediately after filling up with a tank of 10% Ethanol for the first time, but have had consistantly low MPG two tanks of regular since then. Other strongs seem to indicate that the 10% ethanol fuel is not good for Insights, but I haven't found anything about permanent effects, so I'm wondering if this is just coincidence.

Anybody kow where i might best start loking for issues? Nothing else has changed about my driving, local temperatures, etc. I'm at a loss.

 

[originalbadbob]

A few weeks ago, I experienced a similar situation right after a fill up at my normal station. It had gotten colder here in South Carolina, and I expected a drop in mileage, but not 10-12mpg. I was having trouble reaching 70 mpg on my commute (until the temp drop, over 80). When I filled up again from a different station, it immediately went back up to high 70's which is more of what I had expected.

Good luck with it.
robert

 

[jtmco]

During the football game, they said it has been raining in Seattle for 27 days. Any chance there is a relation? Have you been running the defroster? I've had a couple times where my mileage was much lower than "normal" and I usually blame weather (cold or rainy) or the a/c.

Good luck.

Jim

 

[Insightful Trekker]

The combination of the cold and rain are definitely a big part of your losses. However, don't forget the primary O2 sensor does fail without an MIL (Malfunction Indicator Light, (code)). If that is happening then your CATs are being stressed and will rapidly fail as a result. ($,$$$)

Tricky judgment call. :?

Propane enrichment and directly probing the sensors output is the definitive test.

HTH!

 

[tuna1]

Testing Primary O2 sensor

The engine control computer module (ECM) does a proper job testing it as the engine runs.There is no way to test the primary O2 sensor with out disturbing the engine control when it is running,thus changing the values. The sensor does age with use,the responce time will change to changing conditions and lenghten,but the engine control module checks for this and will flag it when it reaches app 100ms responce times.Contaminated fuel will take out the sensor along with the converters,but you won't know until the damage is done.

I have not done the engine ECM recall(nor do i recommend it be done),because it is a better test condition program for the converters but it won't find anything- until the warranties are over,at which time all that is accomplished is your local state has a improved test and reason to fail your car for failure to pass the ODB emission test,when the only one that pays is the owner.

Honda only covers the O2 sensors by law for 3 years/50,000 miles with California Emission package,3/36 with the Federal package,and the converters for 8/80,000 for everyone.Check your Warranties Booklet for your car's model year.I just went around this with a dealer.

 

[sputnik]

Iceberg,
Silver experienced a dramatic drop in MPGs plus lack of Assist when the Lean Air Senser (the LAF) went bad. This problem did produce a MIL light.

Once the sensor was replaced (> 3 years so cost $402 total) the MPGs improved some. It turned out there were other, adjunct IMA issues which complicated Silver's repair, but I agree that the sensors would be a big consideration if MPGs take a sudden dive.

Also the cold...this can cause a lot of daily MPG variation if winter weather fluctuates from day to day as it does in Alabama...one day balmy the next below zero.

Regards

 

[ChristianBaumert]

[Propane enrichment (@ idle ?) and directly probing the sensors output is the definitive test.]

Insightful Trekker :?:

Could you explain the "propane enrichment test" in detail ?


Thank you !

 

[tuna1]

Propane Enrichment test,nor probing the O2 Sensor Don't ....

Propane enrichment test or test probing the wide ban O2 sensors 5wires will not work with the 2000 to 2003 Insights.

Propane enrichment is a basic test to see the responce time of a 4 wire or less O2 sensor.A snap change of the throttle position is another test, a O-scope is required,to see and plot the responce time

 

[Insightful Trekker]

Christian,

Its quite simple. You'll need a propane torch with an short length of hose attached to direct the propane into the intake of the car. Don't light the torch simply feed this "extra" fuel to enrich the mixture.

Monitor the primary O2 sensors output so see the change during propane feed. A scope is better but a fast DMM should be sufficient (you've got to be able to see the spike). If the sensor won't "spike" rich then its bad. There are also some uncommon failures that this test wont completely resolve. You should also test for nominal readings. In rare cases the output can be erratic and unless you get lucky and test _during_ one of the bad phases the sensor may pass.

As tuna1 wrote some type O2 sensors will require monitoring from an OBDII scanner to watch for the spike.

HTH!

 

[green1]

MPG dropped from 60 to 43 fast

This happened a couple months ago, after I returned from NYC to DC. That's a five hour drive. What is entailed in checking the 02 sensors? Just going to the dealer and ask them to do the check? Could another competent mechanic check the 02 sensors, also?