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Kinda rich, no codes?

recent thread got me thinking about an issue with my long gone intrepid
it was a 96 with 3.5 OHC motor. always ran good
kid had it in duluth mn for a few weeks when it was -10F. he flooded motor
i went up and got it started. changed plugs, they were wet
car ran ok but would not idle initially without constant gas pedal feathering
drove it 150miles back to my place and got 15mpg?
had black soot stain on rear bumper from exhaust
no codes. no flashing MIL. ran ok but way down on power
pulled plugs at home and they were BLACK
i drove car for a week and each day it got a little better
what exactly was wrong with sensors? fouled O2 sensor?
extra gas somehow fouled the cats?

Probably an oil burner

ya did read that excess gas will wash oil off cyl walls and effect ring sealing. After a few weeks gas mileage returned back to normal and car seemed to run fine.

Are you sure the engine was not misfiring? If the battery was dead or disconnected the misfire monitor would not be enabled until certain conditions are met and that can be difficult if a misfire is present from the time the battery is reconnected. A misfire will cause the intake vacuum to be low, the computer judges the low vacuum value as a load on the engine and provides a richer fuel mixture.

Possibly. Silicone contamination of the sensor surface maybe.

You might be correct, but I just got my new OBD II Al Santini book this week and he said misfire is a continuous test with no conditions to run.

Kid had run down battery trying to start it after it flooded. We changed plugs, jumped it and held pedal to floor while cranking and it started. Idled ok and I drove it 15min to his house and at that time it would barely idle. I could keep it running and decided to make a run to my house which was 150miles away. Ran so-so on highway and got lousy mileage. I do not recall even a check engine light

In older model cars, fuel injectors can wear out and run rich without a code. I would expect that problem on cars of the eighties which didn’t have OBD. I fixed the problem on an 87 car by changing the $100 injector.

The misfire monitor is a continuous monitor however after a computer reset the adaptive numerator must be learned. The adaptive numerator values involve the minor manufacturing differences in the crankshaft and flex plate/tone wheel. This is learned during deceleration (no load) during engine speeds above 2500 RPMs.

I see Al Santini’s book is $109 on Amazon, for that amount this must be a very detailed book. For details on the specifics of this topic look for information pertaining to Chrysler’s SBECIII controler.

i seem to recall the 96 dodges did not have a maf? they used a MAP sensor and other bits. it is -10f today in mn and it brings back memories of that episode. the dodge was my main car. i had let the kid use it while i worked on is truck so when i got home, i drove it daily from than on. it was not perfect initially. i think it took several weeks to finally settle down. mileage was same as always. the 3.5 was multiport. a fairly good motor. i never had trans issues or headgasket issues with car. got it up to 190k and moved on

I found a used copy for under $50. 163 pages. I don’t know how detailed it is, because I never had an OBD II textbook before. But, I will say I have learned a lot. I knew before how to find the details of a code, but had no comprehension over all, and this book lays it out.

I will look for the information you mention. On a quick reading, I only saw where he listed the three continuous monitors and the fact they had no conditions.

He explained why one should not clear codes on the continuous monitors, if they are the only failures, because so doing sets all monitors to not-ready, and he says good business practices mandate returning the car with all monitors ready. On the continuous, fix them, then run the appropriate drive cycle, then you need not charge for a lot of time to make ready all the monitors.