Hesitation when shifting at high RPM's

I've been having this weird problem with my 95 Z28 (automatic) for a year now. Here is the rundown: When I am driving the car at normal speeds it shifts perfectly. As soon as I floor it and increase the
RPM's up to about 4000-5500 it begins to shake and hesitate erradically before it shifts into second gear at 5800. This continues to happen with the other gears as well. Initially we thought it was a transmission problem, so we spent a whole weekend swapping transmissions with a 94 Z28, but the problem remained. We then switched the ECM computers thinking that maybe someone might have programmed it improperly, but the same problem existed. We also checked to see if the air filter and fuel filter were clogged, but they were clear. I've since talked to a mechanic and he mentioned that it might be a fuel pressure problem, maybe even the fuel pump. Has anyone had this happen to them, or does anyone have any recommendations as to how to resolve this? Any help is greatly appreciated. Thanks.
Michael
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Michael wrote:

First thing to do is to replace the fuel filter. Before you do anything else. But it's too late for that now.....
Second thing to do is to change the spark plugs.
Sure would help if you'd provide some more history on the car, ie miles on the odometer, what maintenance has/has not been done, etc.
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I had the same problem with my 87 about a year after I put in a 383. The problem ended up being the spark plug wires. It just got so hot in there that it wore out the 8mm's so quickly. I put in new 8.8's and it solved the problem...for about two years, im looking into these 11mm's that jegs has.
Check your spark plug wires, then spark plugs, distrub. Im not saying thats the problem in your case, but it was in mine.
justin
Michael wrote:

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I've removed the fuel filter and there was no indication that it was clogged. I've since replaced the coil, the plug wire that connects to the optispark, and the MAF Housing. I'm getting an LT4 Knock Module since I'm about to get the LT4 Hot Cam Kit, so hopefully the problem has to do with that...I'm not banking on it though. The car has about 98000 miles on it. It just had spark plugs and wires installed about a year ago. Fuel, air, oil, and transmission filter have all been changed within the last year as well. If the problem was the distributor, would my normal driving (up to 4000 RPM's) be smooth? Like I mentioned earlier the problem only occurs when I floor it and go above 4000 RPM's. Thanks for all the replies. I'll post the fix as soon as I find one.
Michael
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Hello Michael,
I'm pretty sure that it is a fuel-shortage.
I have exactly the same symptoms with my LPG converted 1975 camaro.
LPG, Liquid Propane gas, is stored in a pressurized tank, and when it is nearly empty, the fuel delivery is reduced. The effects are similar to that what you describe with your gasoline car. The fuel delivery is simply insufficient for a high revving engine. When the pressure in my LPG tank is restored, everything is back to normal for me.
If I were you, I would check my fuel lines.
Bram
On 15 Oct 2003 08:47:56 -0700 snipped-for-privacy@msn.com (Michael) wrote:

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Bram Stolk Spilled my beer when they jumped on the table and

OK. You got my attention. <G>
LPG in an F-body? Mind if I ask a few questions?
How's the mileage/refuel? How hard is it to refuel?
What engine does it have? How's the pre vs post conversion operation? Any noticeable difference?
NOI
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On Sun, 19 Oct 2003 13:58:02 -0400

Sure...
mind you... LPG is a very common thing in the Netherlands, where we have a large natural gas resource, and little oil resources. 95% of all our gas-stations sell LPG, and LPG is almost as popular as Diesel and Gasoline. For American classic cars in the Netherlands, it's the fuel of choice. In fact... an old Camaro in the Netherlands is *MORE* likely to be LPG powered than to be gasoline powered! (New cars with LPG get increased taxes though)

Well.. I was promised a 20% higher consumption, per liter (or gallon), because LPG contains less energy per liter. However, I just consumed my first full tank, and it looks to be a little less favorable.
On gasoline, the '75 camaro did 6km per liter, which is 14 miles per gallon. I have to investigate it a little better, but I expect that it will be somewhat worse than 20% increased consumption. Probably 10 miles per gallon.
Price per liter is approximately a third of the gasoline price, over here.
The tank is 70 liters. The fueling is totally automatic, and easier than gasoline refueling (less spilling). The refueling pump switches off automatically at a 80% fill. So effective capacity is 56 liters, a little less than the gasoline tank. Downside: I have virtually no trunk space left. Suitcases must go on the backseats.

It's a 350 ci V8, 2 barrel carburettor.
I had an Impco system installed.

No, not with a full tank. When the tank is nearly empty, it holds back, and I have to switch back to gasoline. (There is a switch under the dashboard).
Modern LPG conversions do not have a performance penalty anymore, like they used to have in the old days (10 years ago).
Starting takes longer, because there is no choke for LPG operation, and it takes a while for the safety valves to open.
Bram
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Bram Stolk Spilled my beer when they jumped on the table and

Thanks for the info! So, basically, you can switch between gas and LPG? Interesting!
NOI
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