Hey all,
I've noticed that the fuel economy on my '98 Camry V6 (99k mi) has been bad recently. I usually get 24-26+ and I'm seeing 20-22. Work is 1 mile city, 7 miles Highway and then 1 more mile city (9 total). I drive
65-70 mph on the highway and ~45 MPH in the city. I always use 91 octane Chevron gas and try to fill at the same station.My thinking is the car is running too rich for some reason.
Some background checks I did:
I pulled the dip-stick (it's about 3K miles since last oil change, Mobil-1), color is good but I can definitely smell gas.
I pulled a spark plug on the exposed bank and while the tip isn't charcoal black, it is darker than the outter edges of the bent electrodes. The base area of the spark plug, at the very end of the thread (closest to the electrode) IS completely black.
OBD2 testing:
I was able to borrow a friend's OBD2 code reader and I noticed a few things about the Long Term Fuel Trim settings:
At idle/foot off the gas LT FT #1 is usually -8 to -4% while LT FT #2 is
-2% to 0. Under any decent amount of throttle/speed (35 MPH+) LT FT #1 and LT FT #2 are quickly adjusted (almost snapped) to the same, usually
-3%.
Standing still (neutral or park), if I steadily increase the RPM from
2000 to 3500, I can see the LT FT #1 start to go more positive approaching the value of LT FT #2.Does this sound normal? At idle/low-speed should one bank be considerably trimmed more than the other?
Since my driving style is to let off the gas to slow down and then gently re-apply to speed up, I think the ECU is running banks the majority of the time with the idle/low-speed Fuel Trim settings, which seem highly mismatched.
The OBD2 code reader I have doesn't graph data, but looking at the sensor values at speed (45 MPH+), it looks like the O2 sensor after the cat (Bank 1, #2) is relatively slowly varying, indicating (I think) that the O2/feedback system is working correctly (at least at highway speeds).
Is there any easy way to probe the O2 sensors with a oscilliscope or is the OBD2 method the only way? I opened up "DLC1" in the engine bay but the pins for the OX hook-ups are missing (there are just a few terminals with metal contacts).
Finally, I notice if I let off the throttle completely while moving (i.e if I'm going 40 MPH or revving the engine to 2500 RPM then back off the throttle), the OBD2 indicates for a short period the FUEL SYS#1 and FUEL SYS#2 are OPEN (loop) then switch back to closed loop.
Is this also normal?
Suggestions and commentary appreciated.
Jay.