Shakes at 4000 rpm

[thrashmongrell]

I just got a 91 240sx and it has 170,000 miles on it, and while driving if I keep it at 4000 rpms in any gear it loses all power and begins to shake alot acting as if I was in too high of a gear.

It also idles at 700 rpms normally but when I put it into neutral while coming to a stop it will usually fall well below 400 and sometimes almost die.Any help?

[NISTECH]

Welcome to NICO Cody.

The idle issue is likely the IACV [idle air control valve]

the loss of power, you need to take a look at your ignition components and see if they are breaking down under load. see if wire are arching or if your cap has heavy carbon deposits internally. Out of curiosity how fast are you going when it starts sputtering at high rpms?

[thrashmongrell]

Thanks, it usually is the worst in 1st and 3rd, mostly when you try and drive consistently at 4000rpm, around 15-20 in 1st and 40-50 in third, it will not sputter at all when you punch it, only when you hold it there at a consistent speed.