changed oxygen sensors, now seems to be wasting same amount of fuel if not more!

[moff_man]

havnt read through it all but have you tried checking your voltage. . i had a stuffed reg, charging just on 12v and i was getting avarage of 10 on the highway, replaced it now i get as low as 7.9 and an average of 8.5. round town i get about 10 now. only other ting i did was a set of leads at the time but my old leads were still good just i was going on a trip.

also a good way of telling if the engine is in good tune is looking at the tail pipe and seeing if its black, black means bad, my pipe now is slowly cleaning its self back up which means its all good

 

[Michelson4301]

Have the injectors been leak tested ? You need a fuel pressure gauge that reads between 0-100psi minimum. Your exhaust being dirty I believe can be 1 of 2 things, either you got a heap more carby cleaner down 1 bank more than the other although this is very hard to do as the intake holes in the plenum are side by side not staggered. 2 You have an earthing issue. Check it.

You've got or have access to a multimeter.

This is simple and will take 5 mins to check. Turn on your lights to low beam, stereo on(so long as you haven't got a big doof doof in there just a normal 2/4 speaker system), ignition to "on" engine "off", wipers "on", blower fan to "full speed". Now get your multimeter on volts-0-1 v (millivolts scale) and go from battery-to-body and record reading, battery-to-engine and record then body-to-engine. If any of these readings are higher than 100mv you've found the problem.

Had this problem on my car and in the end a new earth cable from battery to body fixed it all up.

Symptoms were Oxygen sensor would read around 600mv's max, no oscillation, changed sensors twice in 2 weeks and was still bad.

 

[admir87]

UPDATE,

ive put the old sensor with the heater earth wire cut, and it was working fine, even after a couple days it was greyish

but now ive connected the heater wire again and now its got a rough idle again... which makes be believe its got to to with the heater wire earth interferring with the signal...

my question is: i never had this problem before, then one day i cut the wire to see if i would get better fuel economy, nothing changed but i left the wire cut... now all of a sudden, if the heater wire to the 02 sensor is connected, there is a problem.... whyy?

 

[Michelson4301]

Poor earth's. Earth that wire in a different location. Might fix it instead of replacing battery cables.

 

[Paiste402]

you shudnt be spraying carby cleaner into ur engine at all......go to Subaru and get some "Upper Engine Clean" that is degisned to spray into ur engine

WAT? dude its carb cleaner ffs. u spray it into the intake and it cleans it out. before giving advice think about what you are saying.

 

[admir87]

ok, im pretty sure now that its the LH o2 heater wires interferring with the signal wires...

is there a reason why the o2 heater is earthed at the ecu or is it just the design?

would i be able to cut the o2 heater earth wire between the plug and o2 sensor, and earth it in the engine bay somewhere? instead of having it disconnected(cut pink wire)

and any ideas on why the problem has come out of nowhere?

cheers in advance

 

[aceventura]

would i be able to cut the o2 heater earth wire between the plug and o2 sensor, and earth it in the engine bay somewhere? instead of having it disconnected(cut pink wire)

Yes you can do this. I have done it just like you said, and immortality has done a much more professional job, see: https://forums.justcommodores.com.au/threads/ecotec-development-5.69960

and any ideas on why the problem has come out of nowhere?

Don't know, maybe the current in the heater is higher in the new sensors and that causes problems??? I think I always had the problems, cause the exhaust was always very black, and now it is much better