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Discussion Starter · #1 ·
i have a all stock 96 impss. and when i drive around town it seems fine power wise. but if i get on the highway and punch it i'll get to about 110 and it will seem to lose power and start to back fire what does this sound like. i dont have any clue. any help is greatful.
 

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The limiter on a SS is well over 110mph. Just fuel pressure. Tape the gauge to the windshield a go for a ride.
 

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First things first, change the fuel filter. Then hook up the guage and go for a drive(high speed pass). At idle pressure should be 37-39, 43-45 with vacuum removed. Should not drop off for any reason. No more no less.

The causes could be reduced delivered volume of fuel, which could be restricted filter, bad pump, leaking/failing in tank hose, failing internal tank electrical harness, and /or redueced voltage supply at pump. It needs at least 12.5 volts. Ideally it should be no more than .5 volts less than battery voltage while the car is running.

Chris
 

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Does it stumble at the top of every gear or just when it gets to 110?
 

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Discussion Starter · #8 ·
just at the top end is when it starts to stumble and lose power its like somthing is holding it back
 

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At around 110, the stock shift tables force an early upshift into OD, which causes the car to nose over right at that point, though it shouldn't be backfiring or stumbling. Is it a general power-loss, or actual backfiring?

As Stone and Rocko pointed out, it's important to determine if it's RPM or MPH dependent. Anything that can cause a high A/F could cause backfiring, i.e. vacuum leaks, dirty MAF, ailing fuel system, even a weak spark.

It's quite possible the condition exists at the top of 1st and 2nd, but in those cases the motor simply isn't dwelling there long enough for the symptoms to be noticeable.

Good luck, and +1 on a fuel filter, just on principle.
 

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Discussion Starter · #12 ·
it starts to lose power and kinda makes a coughing noise i thought it was the rev limiter but i went and started slow to see if i could get over 110 with the rpms as low as possible and it still does the same thing and i only drive in od
 

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Well, when my car does that at the track, it's usually fuel pressure. Like everyone says, get a fuel pressure gauge and see what the fuel pressure is when it starts to stumble. Changing the fuel filter might fix it, but I'm betting your fuel pump is getting tired.

There are several other things that could cause the same behavior, but fuel pressure is both the most likely culprit and one of the easiest to fix.

To make sure, you should get a fuel pressure gauge that has a length of hose attached to it so you can run it through the gap at the base of the hood and tape it to the windshield, so you can take a reading when it stumbles.

Something like this:
http://www.jegs.com/i/Hypertech/533/4004/10002/-1
 
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