Mercury Sable 93 (Taurus) engine knocking/pinging problem

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We drove about a thousand kms on the weekend. Check engine light came on a few times. Here are the KOEO diagnostics codes after the trip: 172 HEGO sensor indicates system lean (RH). (old)
181 Adaptive fuel rich limit is reached (RH). (old) 189 Adaptive fuel rich limit is reached (LH). (old) But this is new: 186 Injector pulse width higher than expected. (this is new) Any use?
I noticed the the performance dropped considerably when engine was hot. Actually one afternoon, when the humidity was high, and weather hot, the car almost was not moving uphill (engine kept running though, knocking of course). Why when the car is cool, the uphill performance is ten times better?. Could that be related to fuel pump as well?
I bought a pair of new o2 sensors, will change them soon.
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take it for a ride up a hill....see how it runs...
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Problem solved! You were right. It was the MAF sensor. I removed the sensor connection, and went for a ride. It behaved much better with no pinging/knocking! (Check engine was always on during that test though). So far, even the engine is hot, car moves when I press the gas. Even can accelarate uphill. Wow, what a difference.
Then I removed the sensor, cleaned according to instructions on http://www.tccoa.com /. Then I put it back. Engine runs almost the same as without the sensor connected, no check engine light. That brings the question: what is the use of that sensor? Why hasn't the computer noticed that it has not been functioning properly?
I happened to buy the O2 sensors the other day, so I will change them too. I don't think they will make a big difference.
Thanks a lot again!
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Very cool!. That sensor tells the computer how much air is going in the engine. It gets dirty and the computer sees less than there really is, thus gives it less gas. I didnt think that year taurus had a MAF, I was talking about the MAP which does the same thing exept it looks at the pressure in the intake manifold. But, either way its fixed! I've seen dirty MAFs cause pinging and performance loss, but never a bad as you discribed. I like to clean them at every tune up.
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Laguna opined in

Ford wisely designed their engine controls so that the engine would operate in event of one sensor failing. The computer was using stored information, throttle position and rpm to measure the fuel mixture. You probably were getting a slightly richer than optimum mixture with it disconnected. The "Map" referred to is used to sense Manifold Air Pressure on cars without a MAF. You have the same sensor but it's used to measure Ambient (Barometric) Air pressure
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So, if I drive with MAF disconnected, my gas mileage would probably be worse, right? Is that it? Because it looks like it is running better like that.
I also replaced both O2 sensors, because they have not been replaced since I bought the car 4 years ago, and they were on sale.
Surprisingly, with the new O2 sensors the performance is worse than with the old ones. I mean there is not much difference, but there is slight knocking under heavy conditions with the new ones. (Anyway, I am not going to put back the old ones, because I had to break the plastic electrical connectors to remove them. Besides it is not worth the labor)
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Im confused, I thought the cleaning fixed it? Mileage would be worse if disconnected, yes.

Slight ping is ok under a load. Again Slight
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Of course problem was fixed. I am just presenting observations about O2 sensors. Let me state the tests results again:
1- Engine runs very good with MAF removed, with old O2 sensors, no knocking at all. 2- Engine runs still very good after MAF cleaned, with old O2 sensors,no knocking at all. 3- Engine runs still good, but not as good as (1) and (2) with new O2 sensors. Does some knocking under slight load conditions. Can't explain why.
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Laguna opined in

the thing needs time to remap... -or- you could disc the battery for 1/2 hour to force it back to default factory
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