Dwell at 60 all the time

Trying to chase down the cause of my poor gas mileage (currently 16mpg). Finally purchased a dwell meter and tested my engine. Dwell is approx 60 when started (cold engine, 80*f outside temp). It varied a little bit for the next ten minutes but not much. It pretty much stayed around 60. I’m guessing the O2 sensor is not operating.

Stage II engine, automatic trans, WOT switch disconnected (it was stuck on causing a high idle condition). Idle is right around 800 and steady once a little warmed up.

I’m going to test the O2 sensor next. Does .5 volts seem right for a warm engine with a correctly operating O2 sensor?

Yes 0.5 volts is about what you get on the narrow band O2 sensor. Since you said your not changing much from 60 deg. I also would suspect the O2 sensor is bad.

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Originally Posted by Bitsyncmaster

Yes 0.5 volts is about what you get on the narrow band O2 sensor. Since you said your not changing much from 60 deg. I also would suspect the O2 sensor is bad.

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Thanks. For the life of me I can not find the O2 sensor connector. I see the wire, but can not follow it. There just isn’t enough room. Can I cut the wire and splice in a new sensor?

You should be able to pull on it until it comes out the rear frame crossmember. Otherwise you could splice the new sensor as well.

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Originally Posted by CFI

Thanks. For the life of me I can not find the O2 sensor connector. I see the wire, but can not follow it. There just isn’t enough room. Can I cut the wire and splice in a new sensor?

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Do you have the rear left wheel removed? You should see the plug socket coming out of the fiberglass tub.

Yes there should be a connector on the drivers side wheel well. If not a PO may have pushed it through into the ECU compartment behind the drivers seat.

I would make a quick check at the WOT switch harness and ensure light green wire isn't grounded. 60 would be the magic number for the lambda enrichment mode. You might have a pinched wire or shorted thermal enrichment switch.

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Originally Posted by Bitsyncmaster

Yes there should be a connector on the drivers side wheel well. If not a PO may have pushed it through into the ECU compartment behind the drivers seat.

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I found it. Someone zipped tied the O2 sensor wire to the left rear spring. I cut the tie, pulled on the wire, and found the connector.

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Originally Posted by FABombjoy

I would make a quick check at the WOT switch harness and ensure light green wire isn't grounded. 60 would be the magic number for the lambda enrichment mode. You might have a pinched wire or shorted thermal enrichment switch.

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Good idea. I’ll double check.

60 % duty cycle is what it would be if the WOT is on. It would not vary at all. Dwell would be at about 54 deg also not varying at all.