Why does my car feel slow at full throttle?

[Machines240]

Well basically at normal throttle, upto about %40 throttle, the car picks up well and is peppy, but past that it feels like its barely accellerating anymore and makes more noise. It is a nissan 240sx with 187k but runs great despite this symptom. Is this from just lack of power (155 hp, 160 lb tq) or is there a solution to this? i was thinking maybe a maintenance item like o2 sensor, ignition or exhaust restriction. so far it has an intake and new spark plugs. anyone know where i am coming from here?

[turboICE]

By no means a complete diagnosis but this sounds an awful lot like my 240sx behaves when the altenator is going. Basically unless the battery is fully charged, there is not enough juice to generate a full spark when the engine is under higher loads. If it is the altenator these symptoms will get worse. I would test the altenator.

[Machines240]

Hmm interesting. not sure the condition of my charge system but i do know that my battery formed a solid white/bluish sand around the neg battery terminal. it doesnt do it much anymore but i wonder i that means anything.
How would i go about to test the alternator?

[m glassburner]

Most auto z--- will test your alt. batt. condition in hopes of selling you something

[David Ferguson]

Clogged injectors can have a similar symptom. Ultrasonic cleaning works.

[badal]

Does it happen in all gears, at the same RPM or just in top gear?
Does it buck or miss?
Cam timing may be off.
Ignition timing could be off.
Fuel filter clogged?
Aifr filter could be restricting things-try a run without it.

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"Bad" Al Bell
ITC #3 Datsun 510
DC Region MARRS Series

[Machines240]

well i dont notice it much in 1st cuz the gear is naturally high. i do noticein the rest of teh gears though. it doesnt buck.
Air filter is brand new and so are plugs. i guess i could try a new filter and maybesome injector cleaner. Any other thoughts?
does anyone notice this with any of theyre cars?

[Tristan Smith]

Check your ECU and see if you have thrown a code. It almost sounds like you are in "limp home" mode. That's were the car runs just enough to get you home.
If the ecu doesn't show any problems, recheck your timing, and make sure your cam timing is correct.

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Tristan Smith
Buffalo's Southwest Cafe
ITA Nissan 240sx #56

[Machines240]

Can the ecu throw codes without the CEL coming?

[Joe Harlan]

1st check compression.
2nd check fuel pressure.
3rd check basic timing.

[7racing]

My vote goes towards a bad alternator. My car had a similar problem and eventually the battery light came on. Changed the alternator and things worked better. I ended up with a much more serious motor issue as well, but let's not go that route just yet.

Jeremy