94 thunderbird 4.6 fuel sys issue

When driving it hard from a stop to about 70mph when the rpm's get to about 3000 or more the fuel system goes into open1 loop then when you back off the gas
it goes back to closed loop. The fuel trims seem to be a little high on one side too I think, will have to watch some more and see if it's just bank two or both. Any ideas as to why it would do this, I don't think this is normal. From what I've read open1 means it's not getting readings from the sensors and is running on the pcm's default. I just had to put a reman by ford MAF on it has been running good since that install, except a little hiccup in the idle while cruising about 35mph this afternoon and the temp gauge dropped and went back up, was kinda spastic. Not sure if it's related. Engine temp reading on the scanner is steady and normal. Any ideas would be helpful. Chris-n-a-flakey-thunderchicken :confused:
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chrisnrali
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chrisnrali wrote:

I've had the spastic temp gage deal several times over the 10 years I've had my 4.6. Weird. No clue what's was happening but I'd say its a good guess in your case its non related. Hasn't happened since I got rid of the factory intake manifold. Coincidence? Guessing not, but......
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WOT can drive the PCM into "open loop - drive" status (not to be confused with "open loop - fault" status).... This isn't an indication that it isn't getting a response from the O2s... It is, however, telling you that it is referring to look up tables and ignoring the O2 sensors... quite a normal condition.
During acceleration, a rich mixture is required... the PCM will drop out of closed loop to avoid having feedback from the O2s leaning the mixture down to stoichiometric.
I'm a little hazy on your fuel trims... is this short term or long term and what do you consider "high"?

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