Weird Dwell Reading

[kbendor]

I can't seem to properly adjust my fuel mixture. Originally I wasn't getting a dwell reading at all. It turns out that my O2 sensor wasn't properly grounded. Once I fixed that problem, the FV started buzzing and I started to get reading. When the car first starts up, I get a reading of 50%. It goes to 60% when I hit the WOT switch. Once the car warms up, the reading goes to a constant 10. Any adjustments I make to the mixture screw doesn't affect the dwell reading. It doesn't pulsate or move at all unless I hit the WOT switch. I replaced the O2 sensor and still having the same issue. The only thing I can think of is the weird ECU wiring inside (see pic). This wiring looks pretty messed up. The car idles good.. Any suggestions?

27745

[DMCMW Dave]

I can't seem to properly adjust my fuel mixture. Originally I wasn't getting a dwell reading at all. It turns out that my O2 sensor wasn't properly grounded. Once I fixed that problem, the FV started buzzing and I started to get reading. When the car first starts up, I get a reading of 50%. It goes to 60% when I hit the WOT switch. Once the car warms up, the reading goes to a constant 10. Any adjustments I make to the mixture screw doesn't affect the dwell reading. It doesn't pulsate or move at all unless I hit the WOT switch. I replaced the O2 sensor and still having the same issue. The only thing I can think of is the weird ECU wiring inside (see pic). This wiring looks pretty messed up. The car idles good.. Any suggestions?

27745

That excess wiring is the power antenna.

50% is normal for cold. 60% is normal for full throttle (actually normal is 45 and 55 but meters seem to vary). Constant 10 means that the ECU thinks it is way too rich.

If you are turning CCW (lean) enough that it stumbles, and then CW enough that it stumbles (rich) and the ECU is still running full lean (i.e. reading 10-20), you need to check the ground wiring (the small ground wire on the back of the pass side intake runner), and maybe swap the ECU with someone as a test. Make sure the huge plug on the ECU is seated all the way in the ECU.

You can test the ECU by alternately grounding the O2 connection and putting a 1.5V battery on it (with the sensor disconnected). If those tests pass, the ECU is good. This test is in the manual on page D:04:15. For some reason nobody ever sees this one.

The other possibility is that it really is running crazy rich on one cylinder no matter how you set it ( i.e. stuck injector) and throwing off the reading, but if that's the case it should not be running very well.

[Bitsyncmaster]

Your meter must be reading duty cycle. 50% is correct for cold engine, 60% is correct for WOT. I agree with Dave S....your just way off on the mixture adjustment. Normal for the adjustment range to be less than 1/4 turn. Meter will read about 10% below that adjustment and 90% above the other end of the adjustment.