O2 sensor bad= poor gas mileage

Conga1991 · 02-06-2012, 03:02 PM

What I have is a 86.5 Supra with a rebuilt 7mgte, 57 trim, driftmotion ic set-up, 3inch exhuast all the way back (too loud for my taste) and a intake. Haven't changed the fuel pump yet, it's still the N/A pump but have a walbro fuel pump to drop in.

So, I've searched and came with nothing. I have replaced my O2 sensor a few times, it works great up until I hit boost (stock) and my cel comes on. once that does I get really shitty gas mileage, Im talking 220 miles to the tank at the most. When my O2 sensor didn't go out the needle on my gas gauge would just stick forever and not budge. Can anyone chime in on what could possibly be the problem? All help is definitely appreciated since I'm moving down to Arizona for school and don't want anymore poor mpg

cre · 02-06-2012, 08:53 PM

What you describe isn't consistent with a bad O2 sensor.... It's more consistent with a bad AFM, excessive engine knock, bad knock sensors or wiring, etc.

Have you bother pulling the diagnostic codes? If you don't know how look in the MKIII FAQ section for a thread on how to do it.

Conga1991 · 02-06-2012, 10:36 PM

Yes I have, I have a code 34 and 41. I just remembered I pulled the cps out and didnt jump the terminals for timing. Ill jump it, start it and see if there is any codes after that and let you know.

cre · 02-06-2012, 11:38 PM

34 is most likely the issue and timing isn't going to cause it.

Conga1991 · 02-10-2012, 11:29 PM

Okay, I'm using the stock 7mgte afm but with the Lexus electronic. Is testing the resistance on the Lexus the same as the stock 7mgte meter? Of course Im testing it now to make sure its in spec, if it is the same as the 7mgte's.

Im also running an upgraded ct-26 with a 57 trim.

cre · 02-11-2012, 12:15 AM

Yes, the actual sensor is the same... Same part number even. The method of testing in the TSRM isn't 100%... You'd need an oscilloscope and Toyota's advanced diagnostic publication to really test it. Has the air bypass screw been tampered with?

02-06-2012, 03:02 PM	#1
Conga1991 3" Exhaust Join Date: Jun 2009 Location: Avondale, AZ Posts: 169	O2 sensor bad= poor gas mileage What I have is a 86.5 Supra with a rebuilt 7mgte, 57 trim, driftmotion ic set-up, 3inch exhuast all the way back (too loud for my taste) and a intake. Haven't changed the fuel pump yet, it's still the N/A pump but have a walbro fuel pump to drop in. So, I've searched and came with nothing. I have replaced my O2 sensor a few times, it works great up until I hit boost (stock) and my cel comes on. once that does I get really shitty gas mileage, Im talking 220 miles to the tank at the most. When my O2 sensor didn't go out the needle on my gas gauge would just stick forever and not budge. Can anyone chime in on what could possibly be the problem? All help is definitely appreciated since I'm moving down to Arizona for school and don't want anymore poor mpg

02-06-2012, 08:53 PM	#2
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	What you describe isn't consistent with a bad O2 sensor.... It's more consistent with a bad AFM, excessive engine knock, bad knock sensors or wiring, etc. Have you bother pulling the diagnostic codes? If you don't know how look in the MKIII FAQ section for a thread on how to do it. __________________ If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum. If you're so inclined I'm always more than happy to accept tips via PayPal. Tip Jar --->

02-06-2012, 11:38 PM	#4
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	34 is most likely the issue and timing isn't going to cause it. __________________ If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum. If you're so inclined I'm always more than happy to accept tips via PayPal. Tip Jar --->

02-11-2012, 12:15 AM	#6
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	Yes, the actual sensor is the same... Same part number even. The method of testing in the TSRM isn't 100%... You'd need an oscilloscope and Toyota's advanced diagnostic publication to really test it. Has the air bypass screw been tampered with? __________________ If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum. If you're so inclined I'm always more than happy to accept tips via PayPal. Tip Jar --->

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02-06-2012, 10:36 PM	#3
Conga1991 3" Exhaust Join Date: Jun 2009 Location: Avondale, AZ Posts: 169	Yes I have, I have a code 34 and 41. I just remembered I pulled the cps out and didnt jump the terminals for timing. Ill jump it, start it and see if there is any codes after that and let you know.

02-10-2012, 11:29 PM	#5
Conga1991 3" Exhaust Join Date: Jun 2009 Location: Avondale, AZ Posts: 169	Okay, I'm using the stock 7mgte afm but with the Lexus electronic. Is testing the resistance on the Lexus the same as the stock 7mgte meter? Of course Im testing it now to make sure its in spec, if it is the same as the 7mgte's. Im also running an upgraded ct-26 with a 57 trim.