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Discussion Starter · #1 · (Edited)
My 2004 Taurus with 49k miles is having difficulty shifting gears. I have to increase the RPMs to about 3k and then take my foot off the accelerator for it to change to higher gears. I took it to a reliable transmission shop, and the experienced transmission mechanic told me to take it somewhere to diagnose what he believes is a low-power issue. Any advice on how to proceed to check for this issue? P1000 consistently shows up.
 

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Discussion Starter · #3 · (Edited)
I am working on trying to diagnose the low power issue. I am looking at a blocked catalytic converter. Is the O2 sensor 2 responding normally? Not cycling?

I am not sure how to interpret the barometric pressure. Is this supposed to match the outside pressure? My outside pressure is very close to 30inHg.

Both sensor voltages vary between 0.1 and 1.0 volts.

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sensor two shouldn't cycle. Should stay near half range once it's warmed up. Looks fine to me.
Pic of sensor #2, top chart with bad O2 sensor, below chart is with that sensor replaced. So the bottom chart is normal S2 behavior.
As to why in the first case, one bad sensor causes the other to give up after a short time. No idea.
As I understand, S2 monitors the performance of S1. I have had over the years, S1 fail, and S2 fail but not at the same time. ( have had/have 6 G-4's so had my share of practice).
-chart-
 

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Discussion Starter · #6 ·
I did some monitoring of the MAF sensor. I have graphs below for before and after cleaning with a MAF cleaner spray. Barometric readout is very different before and after cleaning. Is the MAF response vs. throttle one would expect? The car still is not getting enough power, I believe.
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Discussion Starter · #7 ·
I got a new MAF sensor installed and no improvement. Still that weird drop in baro pressure and I think the MAF not high enough? About 6 lb/min max at full throttle. The outside air temp is about 35F. Not sure why temp dropped. Weird pressure and temperature responses that I cannot figure out.


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Sprayed the outside intake/throttle area with carb cleaner to test for vacuum leaks. No change in engine response detected.
I removed the air filter and left the clamps open to see it MAF would incerase. It did not:


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Discussion Starter · #8 ·
It was a blocked catalytic converter. A local transmission place took it out for a ride and suggested this might be the reason. I took it out and soaked it in about 10% nitric acid (can probably use diluted muriatic acid instead, but wear gloves and goggles) overnight, then rinsed it very well with water. A world of difference now. Thanks, everyone, for giving me your thoughts!
 
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