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My 96 Impala is my first B Body with a tact. Mine seems at idle to be at a normal RPM. What should the RPM be running at say at 60-70 mph? When I floor it, not hammering, but say hitting the passing gear that tact will bury into the 7k range. Is that right? The motor sure does not seem like it is doing that high of RPM. I think when I am at HWY speed in OD, the RPM is like 3500 or so. That seems high and again the motor does not sound liek it is rev'ing up that high.
What is the deal. I am new to this car year so I have no clue what is right or wrong?
 

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Something is wrong with your tach. Assuming your car is stock, your PCM would cut off fuel at about 5500 rpm. At freeway cruise you should be about 1500-1700 rpm?

Unless you have really steep gears and your motor is built with a custom pcm tune, those numbers are way off.
 

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I had a tach do basically the same thing. I changed the circuit board on the back of the instrument cluster. It was cheaper than the whole unit at the PNP JY. It still works good a year later. If you post a picture, I am going to the JY tomorrow (Thursday Dec 24) morning at 7:30. If there is one like yours, I will get the board for you at a reasonable price.
 
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Discussion Starter #4
Something is wrong with your tach. Assuming your car is stock, your PCM would cut off fuel at about 5500 rpm. At freeway cruise you should be about 1500-1700 rpm?

Unless you have really steep gears and your motor is built with a custom pcm tune, those numbers are way off.
At freeway it is running if I recall like 3500 but I know the motor is not. I owned a 94 lt1 bbody before and it runs like that one. It is not rev'n high. It is all stock as far as I know, from what I was told.
 
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Discussion Starter #5
just aroudn the hood here, if I get on it it, it goes up to the 7k range, ha ha ha, even thought the motor is not.
 

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OBD1 PCM conversion without the tach correction???????
 
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OBD1 PCM conversion without the tach correction???????

R U asking me a question? ha ha ha

Isn't 96 OBDII ???? I am fairly sure the car is all orig, not PCM mods. It idles like around 1100-1300 I think. That seems right?
 

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so the most likely culprit is a bad board?
It very will could be. The only way you can find out is to change the board, or replace the entire instrument cluster. The cluster is easier, because you do not have to take it apart, but the board is cheaper because you do not have to buy as much stuff.

My cluster acted in a similar fashion, and the board fixed mine. It is only a comparative situation. It could well be something else, but is appears similar enough to be the same problem.
 
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Discussion Starter #13
tach issue was due to the car having a 1996 CAMARO PCM in the car. Reflashed to be a SS and all good now!
 
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