So after driving my 280z from Florida to Tennessee my car (and it didn't break down!) I've realized that my car actually starts going slower once i push the pedal more than 3/4 of the way down. Even when I'm cruising at 65 on a flat high way. Also, It is having a very hard time making it up moderate sized hills at 3-4K RPMS.
No vac leaks, the car usually runs a little sluggish. I while driving up here there were fairly steep hills on the high way, and my car wouldn't even go 40 up them.
I suppose i'm just looking for suggestions as to why I seem to be missing a bit of power, and why it decelerates once the gas pedal is pushed far in.
Any suggestions would be appreciated.
I really can't think of any other information to provide that i think could be helpful.

thanks guys.

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1978 280Z 5speed Daily Driver
Clarksville, TN
Z on a budget!

do engine RPM's stay up as the car slows? could be clutch slipping.

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http://community.webshots.com/user/stupid126

I would suspect fuel pressure. You'll probably notice that it's happening at about 3200rpm.
If so, the tps is a switch that is fuel/no fuel/go baby go depending on throttle position. They provide signal to the injectors. They fire at low rpm/idle and to start pulling the car alont. Cruising speed, the injectors don't get signal to fire and then at aprox 3200rpm (exact number is in the factory service manual) and so if the injectors get the command to fire but the fuel pressure and supply aren't there, it won't have fuel to get the power you need.

Put a guage on the fuel line between filter and fuel rail. Do a pressure test as per the factory manual.
Download it free at www.xenons30.com as well as the fuel injection guide lower on the reference page.
Ten to one, your problem's in the fuel system.
If the problem is not with pressure, test to see if the injectors are firing when they get signal to fire

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Edmonton, Alberta, Canada.
My main areas of knowledge involve the ZX.

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Edited 1 time(s). Last edit was february 07, 12:56pm.

You might also want to take a look at a spark plug and the cap/rotor. You *could* have a weak spark not wanting to ignite the mixture under heavy load...

This probably isn't it. But when I brought my 82 down from Chicago it had lost power by the time we got here, wouldn't go up hills. One of the plugs had been pulled at the cap but not inserted all the way back in. By 600 miles it had eaten through the wire mount on the cap. So if there is a crack in the cap, that might cause that too.

But my bet would be on the TPS.

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Chattanooga, TN
82 white w/ red n/a coupe 120,000 miles.
83 2+2 314,395 miles at college AGAIN
96 Pathfinder, 96 Maxima
90 300ZX 2+2, 82 ZXcoupe, 81 200sx, 72 Camaro SS, 68 Mustang, 1950 Chev PU fully restored
Pics:[www.zcar.com]

Fuel flow rate is my guess. You can easily have full pressure measured at the rail, but insufficient gallons per minute of flow.

Besides the big fuel filter under the hood, you need to check to be sure the pump is not being obstructed by tank crud and varnish and such. On the ZX cars, there is a screen strainer on the end of the pickup tube inside the tank. It can become clogged, starving the system of fuel at high rates of consumption. Also, in the ZX, there is a fuel strainer sock just inside the fuel pump's inlet nipple from the tank. It can become full of crud that gets past the in-tank strainer.

I don't know if the older 280Z cars have both of these "extra" filter elements or not, but it is something to consider. You need to carefully check the condition of the insides of the tank, also. It might be necessary to professionally clean and seal it. A common problem after all these years.

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Bob, in San Diego
1983 280ZX Turbo Coupe 5 speed

Visit [xenons130.com] for ZX Manuals, or
[www.xenons30.com] for 240Z, 260Z, or 280Z manuals.
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Maybe it's time to go to "position 2" on the cam. Norm K.

Pos 2 wouldn't make a difference in this case.

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Chattanooga, TN
82 white w/ red n/a coupe 120,000 miles.
83 2+2 314,395 miles at college AGAIN
96 Pathfinder, 96 Maxima
90 300ZX 2+2, 82 ZXcoupe, 81 200sx, 72 Camaro SS, 68 Mustang, 1950 Chev PU fully restored
Pics:[www.zcar.com]

What would position 2 be doing?
Thanks guys, my car isn't willing to start so far today because it's covered in ice. Time to go get the clip to fix my cold start valve it seems, and hopefully i'll be able to get a pressure gage to test the fuel rails etc today..

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1978 280Z 5speed Daily Driver
Clarksville, TN
Z on a budget!

Perhaps timing is off? Had a simular thing happen to me and my 74 Vega GT wagon. It just would not go up a hill without bogging down,timing was way retarded. May not be your case but,a good place to start.

They say to goto Pos when you get some miles on it. I played with it for a while. Seemed to be a bit more responsive but dropped my gas mileage about 1.5. I think I moved it back.

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Chattanooga, TN
82 white w/ red n/a coupe 120,000 miles.
83 2+2 314,395 miles at college AGAIN
96 Pathfinder, 96 Maxima
90 300ZX 2+2, 82 ZXcoupe, 81 200sx, 72 Camaro SS, 68 Mustang, 1950 Chev PU fully restored
Pics:[www.zcar.com]

Yes, timing does sound like a possibility, because think about it, when your at part throttle the vacuum advance is functioning, giving you 8 or so degrees of extra advance. Then when you floor it, there is no vacuum advance. Maybe that would explain why it seems slower at full throttle.

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'71 240z: Stock L24, Ztherapy SU carbs, MSA Twice Pipes, 6-1 Header, Tokico Struts, Eibach Springs, Hawk Brake Pads
'06 Frontier: Stock
'34 Ford Coupe 5/8ths scale replica race car (Legends Car)

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