02 Volts are inconsistent

[chipsbuick]

I have a 1987 Gn with 009 Injectors,hotwire 340 pump,adj fuel press reg, TH downpipe. Last month I ran 12.32 at 108 mph on drag radials. This was with a stock turbo and intercooler. I recently put on a Front mount intercooler and dual fan setup. I started noticing the 02 volts as low as 250 at full throttle. Then the next pass they would return to normal. Can any one help me trouble shoot this. I have good voltage from alternator and at fuel pump. The fuel pressure in the rail is 70 psi at 20lbs of boost. Also I tried 2 chips and had same result. reds 93 and reds 108 race chip. The mass air numbers on the scanmaster look normal. I am not sure what the issue is. Any help would be appreciated.

Thanks,
Turbo Chip

 

[norbs]

Maybe the sensor is going bad. BUt you shouldn't really use it to tune, you should use a wideband in the dp instead to be safe.

 

[Quick6'n'-K.C.]

Depending on how long you stay in the throttle, and what scantool you are using, that will effect what the low 02 reading may be.

Such as using a scanmaster 2.1 that might catch your lowest 02 at 0mph, which might be the low 02 reading. Press BOTH buttons, then that tells you at what MPH both the low 02 and the highest knock retard was at.

If you notice that during a run, the 02 millivolts drop from 800 to 250 during a pass, no knock, check the grounds at the back of the pass head, lift the harness up and there should be wires that are grounded.

Also check the pin connection at the ECM to make sure its not loose.

BW

 

[chipsbuick]

O2 Milivolts

Thanks for the feedback.

The 02 sensor was replaced with a denso and the same problem is apparent. I also noticed that if I start the car run it after just a few minutes it seems OK. After four or five wide open throttle runs the problem begins and gets worse. Do you think the fuel pump is damaged?

At the track with race gas I had no knock with the 250 counts. The car lost power and the et's were slower by 3 tenths.

Thanks for the help,

chip