3.4l loss of gas mileage...
#1
3.4l loss of gas mileage...
I have had a significant decrease in gas mileage for a long time. I had a really difficult time passing smog a few months ago:
-new plugs
-new cat
-new muffler
-new 02 sensor
-new air filter
-new MAF sensor
After all that work it passed smog.... barely.
15 mph - RPM 1550 CO2 14.7 HC 50 CO 0.59 NO 0
25mph - RPM 2435 CO2 14.8 HC 30 CO 0.49 NO 1
I am concerned it will not pass smog next time. I would like to get my fuel mileage back and figure out why HC is running so high. Also, I know the timing is spot on. No CEL or codes on the OBD scanner.
The move to a different state comments on smog are not helpful. Just looking for some advice to get my gas mileage back.
-new plugs
-new cat
-new muffler
-new 02 sensor
-new air filter
-new MAF sensor
After all that work it passed smog.... barely.
15 mph - RPM 1550 CO2 14.7 HC 50 CO 0.59 NO 0
25mph - RPM 2435 CO2 14.8 HC 30 CO 0.49 NO 1
I am concerned it will not pass smog next time. I would like to get my fuel mileage back and figure out why HC is running so high. Also, I know the timing is spot on. No CEL or codes on the OBD scanner.
The move to a different state comments on smog are not helpful. Just looking for some advice to get my gas mileage back.
Last edited by GoudyMan; 06-14-2012 at 02:25 PM.
#3
#4
Registered User
seafoam gotcha.
the scanner, my question is, can you check air fuel ratio afr to make sure ecm is not in limp mode, or in open loop with the scantool?
iirc supposed to be in open loop not the default (rich) closed loop safety mode.
the scanner, my question is, can you check air fuel ratio afr to make sure ecm is not in limp mode, or in open loop with the scantool?
iirc supposed to be in open loop not the default (rich) closed loop safety mode.
#5
i do not know how to check the air fuel ratio?????
#6
Contributing Member
Try resetting the ECU, pull the EFI fuse and then turn the key to the on position a few times to drain the residual charge in the ECU.
If you use the scan tool it will have a a lot of stuff to look at, just make sure everything seems normal.
Coolant temp should be around ~180-200
Long term and short term fuel tirm is also important
It will also tell you if it is in closed loop or open loop mode (open loop is for cold starts and WOT pulls, Closed loop is for everything else. It runs a lot richer in open loop)
If you use the scan tool it will have a a lot of stuff to look at, just make sure everything seems normal.
Coolant temp should be around ~180-200
Long term and short term fuel tirm is also important
It will also tell you if it is in closed loop or open loop mode (open loop is for cold starts and WOT pulls, Closed loop is for everything else. It runs a lot richer in open loop)
#7
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Join Date: Nov 2010
Location: Columbia River Gorge, Oregon...east side
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Closed loop described on page 15 and open loop on page 16:
http://www.autoshop101.com/forms/h25.pdf
Also useful:
http://www.4x4wire.com/toyota/4Runner/tech/OBDII_ECU/
Last edited by rworegon; 06-15-2012 at 05:23 AM.
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#8
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OP, do you have any vacuum leaks? A small crack in a hose or the intake hose causes unmetered air to enter the system and can do strange things.
New PCV valve?
What plugs were used when changed?
Have the plug wires ever been changed? How many miles on them?
Are you using any coolant?
Fuel injector issue i.e. stuck open?
High HC troubleshooting, page 2:
http://www.ncttora.com/fsm/1996/SIL/.../cohc/insp.pdf
New PCV valve?
What plugs were used when changed?
Have the plug wires ever been changed? How many miles on them?
Are you using any coolant?
Fuel injector issue i.e. stuck open?
High HC troubleshooting, page 2:
http://www.ncttora.com/fsm/1996/SIL/.../cohc/insp.pdf
Last edited by rworegon; 06-15-2012 at 05:37 AM.
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