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Smog fail on 91 Comanche


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11 hours ago, Inadaze said:

Awesome, every 2nd year I always sweat bullets. :L: I forgot to to ask if it was Auto or Manual, RPMs on the 25mph 2305 rpm on the Fail vs 1478 on the pass the lower RPM also could of played a roll in the Pass also. I Love to see these on the road, I have a goal to have as many or more as Fiatslug !!! Hopefully we get one in over at Fairfield PnP, meetup, and tag team it and save a little bit of history :wink: 

Manual. And yeah those lower rpms seem to have helped. Anyweays, i know who to smog it with next time .

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  • 2 months later...

I have not passed smog and I am reviving my old post looking for help.   Quick rundown, it passes everything except 25mph in second gear, which is about 2,000 RPM.  Test results have high NO and no CO - indicates a lean condition.  It's threw a lean code a year ago and we replaced injectors with 4 hole and fixed vacuum leaks in the fuel rail, regulator and a couple hoses.  Could hear the leaks before but now can't hear any.  I've used a smoke machine and it looks like I have that eliminated and I have not had another code. 

 

Most advice was either vacuum or O2, so I tried to test the O2. I had some trouble back probing the O2 sensor to test the low voltage wire (high voltage and grounds were OK since I could test unplugged).  Yesterday we were at the JY getting some parts for my daughters 1995 XJ and I snagged both plug ends for the O2 sensor to make a connector with pigtails I can test with.  Using a digital multimeter we were getting +12V on the high voltage (more like 15v).  I used the analog meter (Gardner Bender GMT318) on the low voltage and it swung 0 to 1 at idle and and .4 to .5 at 2,000 RPM, but every second or two it would spike to 1v.  So is this analog meter up to the task, and if so does the occasional swing to 1V create my lean condition?  Thanks!

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18 minutes ago, oldmanche said:

but every second or two it would spike to 1v.  So is this analog meter up to the task, and if so does the occasional swing to 1V create my lean condition?

 

1vdc on O2 would indicate going RICH. Maybe its trying to correct for the LEAN condition.

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