From 50+ down to 41 mpg !?!?

[mpdonalson]

Over the last 10,000 miles my cars mileage has gone from 55 mpg (its a CVT) down to 41 mpg and has gradualy lost power and is using assist more. My '94 Metro is blowing it away on mpg!! This is an everything perfectly by the book or better maintaned car, everything means everything. Always OEM fluids and filters. Please dont make me repeat this. Cats and o2 sensors are original. IMA pack died suddenly and was replaced 30,000 miles ago and nothing changed after. Tires OEM at 40PSI ALWAYS. This is a commuter car that is driven the same route 82 miles per day 5 days a week at the exact same speeds with the exact same acceleration and braking habits. Mileage always stayed at 55 mpg. Same fuel from same place always. Tried a different place for fuel for 2 tanks to verify fuel was not the issue. Previously the seasonal fluctuation was about 4 mpg. Clogged cat(s)? Worn o2 sensor(s)? Bad injector(s)? Valve lash? Its not noisy. Does idle kind of rough (3 cylinder...) but not any different than before. I can not afford to just start throwing expensive parts at it. I would like to know test procedures or where to get them for any uncertain suggestions. Car has 91,000 miles and is a 2003 with CVT. Please help me.

[Eli]

No CELs?

Do CVTs have trouble with clogged EGR plates like MT cars can?

It's only a few hundred to rebuild the cat. P0420's are going to be the only obvious symptom of a clogged cat, it won't be possible to diagnose if that's your problem other than having it rebuilt will fix it.

[mpdonalson]

No CEL. No codes. Have owned car in the past with bad cat with no code or cel but it was not an Insight...

[Eli]

Hmm. Seems like it would be throwing codes with a clogged cat, since the Insight is so sensitive about its cats. I guess it's possible not though.

So you're at 100k miles.. I assume the spark plugs haven't been changed yet? It'd be good to do a general tune-up on the car if it hasn't been done yet.

My bet is either on the EGR system or the cat. It would be throwing codes if the O2 sensor was going out.

[ghammerly]

I would check
1 EGR system valve function and circuit not clogged.
2 Fuel injectors clogged or poor atomization, also fuel pressure.
3 Catalytic converters (unlikely)
4 Plugs (unlikely)
5 Rolling issues such as bad wheel bearing, dragging brakes, toe in or out.

[Jivko57]

You can check deeper on that rough idling. It is 3 cyl but mine is idling fine after 240k miles on the clock. Yours should be even better.
Could be:
- one of the spark plugs or the coils is going bad.
- EGR plate is clogged( CVT should have similar EGR system...)
- IMA battery or 12v battery is deteriorated and the car is charging constantly.

......

[mpdonalson]

Plugs about 15,000 miles ago. They are all A. OEM (everything means everything) Torqued to spec. Sqeaky clean EGR.

[mpdonalson]

1 EGR clean
2 How do I test injectors?
3 How do I test CAT CONs?
4 Plugs are recent and proper.
5 I am a steering, suspension and brake tech...

[mpdonalson]

Plugs recent and proper. How do I test coils?
EGR system recently cleaned. (dont know if different than MT)
IMA pack 30,000 miles ago. 12 volt battery 15,000 miles ago.
IMA charge still never gets below 3/4 on guage and used to rarely use assist unless accelerating hard. Was almost always at full charge untill recently. Seems again as if ICE is not puting out enough power.

[mpdonalson]

I have access to a Genisis at work. I think it will show me live readings. Anybody know what I should be seeing as far as o2 sensors?