7mgte problems

Jedd · 05-19-2011, 04:08 AM

Hey Guys, I'm new here and was hoping you could help me out.

I work primarily with diesel engines, I know enough about gas engines to get around them. I'm working on an 89 7mgte installed in a 4runner. Engine is completley stock except for a walboro 255 fuel pump SAFCII and the boost turned up to 10psi. AEM wideband A/F, Autometer pyro

Problem: No matter what I do I can not get the engine to not run lean. Except for unplugging the 02 sensor then I get extream rich (10.1 on gauge) and the engine will barely idle

Taking voltage readings off the stock o2 I get fluctuations between .1 - .5 volts (I understand stoich should be .45) at this time my A/F gauge reads between 16.1-off the chart lean.

I changed the output setting on my gauge to put out 0-1volt and wired it into the ECU in place of the stock o2 sensor and it still reads lean, just much more controlled (no bouncing around like your stock o2 sensor.

Pyrometer readings are about 600F at idle and under full load boosting at 10psi it gets up to 1300F and around 1000F cruising. (obviously these are short readings for testing since i'm unsure about the lean readings.)

any help would be awsome. Thanks

El Supracabras · 05-20-2011, 01:51 PM

Any codes? Fuel pressure reading? A/F's at WOT? Vacuum readings?
You may have went that rich when unplugging the o2 because of the SAFC. It is only effective in open loop. If you have the low throttle set to add fuel the computer might fight to keep it stoich in closed loop. The more you add, the more it will try to remove. Try unplugging the SAFC's KVAFM leads at the computer and connecting it back to the stock configuration. This will eliminate the SAFC's control of the sensors signal to check if it is messing with your computer. It has happened before.
Don't rule out the possibility of defective wide band o2 sensor. I've killed a couple of the bosch ones from "experimenting" (they come with the AEM W/B kit) and they both started reading leaner before they went bad. Being so close to the turbo can do that i guess. AEM has a video on youtube showing how to test your WBo2 sensor with brake cleaner, its pretty cool.
I usually read between 14.7 and 16. when cruising which I think is pretty good and pretty solid 14.7 at idle (once completely warmed up).
These are a just a few of the things I encountered with sketchy wide band readings, hopefully they help. Good luck.

05-19-2011, 04:08 AM	#1
Jedd Stock Join Date: May 2011 Location: Canada Posts: 1	7mgte problems Hey Guys, I'm new here and was hoping you could help me out. I work primarily with diesel engines, I know enough about gas engines to get around them. I'm working on an 89 7mgte installed in a 4runner. Engine is completley stock except for a walboro 255 fuel pump SAFCII and the boost turned up to 10psi. AEM wideband A/F, Autometer pyro Problem: No matter what I do I can not get the engine to not run lean. Except for unplugging the 02 sensor then I get extream rich (10.1 on gauge) and the engine will barely idle Taking voltage readings off the stock o2 I get fluctuations between .1 - .5 volts (I understand stoich should be .45) at this time my A/F gauge reads between 16.1-off the chart lean. I changed the output setting on my gauge to put out 0-1volt and wired it into the ECU in place of the stock o2 sensor and it still reads lean, just much more controlled (no bouncing around like your stock o2 sensor. Pyrometer readings are about 600F at idle and under full load boosting at 10psi it gets up to 1300F and around 1000F cruising. (obviously these are short readings for testing since i'm unsure about the lean readings.) any help would be awsome. Thanks

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05-20-2011, 01:51 PM	#2
El Supracabras 3" Exhaust Join Date: Feb 2010 Location: Chicago Posts: 240	Any codes? Fuel pressure reading? A/F's at WOT? Vacuum readings? You may have went that rich when unplugging the o2 because of the SAFC. It is only effective in open loop. If you have the low throttle set to add fuel the computer might fight to keep it stoich in closed loop. The more you add, the more it will try to remove. Try unplugging the SAFC's KVAFM leads at the computer and connecting it back to the stock configuration. This will eliminate the SAFC's control of the sensors signal to check if it is messing with your computer. It has happened before. Don't rule out the possibility of defective wide band o2 sensor. I've killed a couple of the bosch ones from "experimenting" (they come with the AEM W/B kit) and they both started reading leaner before they went bad. Being so close to the turbo can do that i guess. AEM has a video on youtube showing how to test your WBo2 sensor with brake cleaner, its pretty cool. I usually read between 14.7 and 16. when cruising which I think is pretty good and pretty solid 14.7 at idle (once completely warmed up). These are a just a few of the things I encountered with sketchy wide band readings, hopefully they help. Good luck.