Help - 1990 300ZX engine sputters at high RPM's
 

I was referred to this message board by someone on the news groups. I hope this 300ZX question is not out of line on this board - thanks! My 1990 non-turbo zx has 99k, has been reasonably well taken care of
and has given me very little trouble over the years. Recently it has
begun to die out at rpm's over 4k. It acts almost like it is hitting a
rev limiter. If I let off the gas a bit the rpm's will begin to climb
some, but obviously with little power. The problem seems to be worse in
higher gears suggesting power might somehow be involved. If I rev it
with the clutch in, no problem - flies high. Also - when the RPM's
stop going up - the car stops accelerating (as you would figure!)
however it sounds like something is still revving up... Very strange. If it
were not for the RPM needle not going up I might think it was
transmission related but this definitely feels like the engine. What does this
sound like? Any chance its fuel injectors or something? Could it be
plugs? The plugs only have about 30k on them, but it has taken a long
time to put those miles on - maybe they needed cleaned? Any ideas
would be helpful - thanks!

Chris.

You'll probably have more success on ZCar.com or TwinTurbo.net - both of those have forums that cater to the 300ZXs.

Fuel pump? check [43.4 psi] pressure at WOT all the way to redline.

did you say that your SPARK PLUGS have 30,000 miles on them?!!! Change them!!!

BTW you would have better luck here
http://www.300zxclub.com/

Amen brother, those things are terrible about fouling plugs.

lol. a REALLY good Nissan tech told me 9 out of ten times when you take it in for spark plug changes they NEVER change the rear spark plug for the passenger side bank Ithink, cause it is SO hard to get to and they can only charge a certain amount and it takes too long.

that is why those cylinders are always weaker on those cars.

spark plugs and fuel pump are good, what about coils? possibly damaged also wiring. could be rotting wiring. did the car sit long?

sounds fuel delivery related. the rev up sound you are hearing is prolly your throttle plate opening and letting more sound out of the motor.
check fuel pump and filter or fuel sock.

Fuel pump replaced
 

Had the fuel pump replaced. It improved the situation, in fact at first I thought it was all better. Now, when the engine is cool it will grant most power all the way to redline. When it warms up - will not pass 4500 RPM under WOT in 3rd gear. If I let back on the gas a bit I can get the R's to climb slowly. Still have extra sound at WOT.
Does that fact that the symptoms are worse under WOT as compared to not give any direction as to what the problem could be? I am going to take it in to have it looked at but I would like to offer the mechanic some direction - as you guys may know more about this car than my mechanic (I hate the local dealer).

Thanks again!

Chris.

Any check engine lights? Have you checked the MAF

Could be a bad mass airflow sensor to me. Follow Dave's advice (DavesZ#3). The Nissan consult should pick it up.