PLEASE HELP! Z32 loses power...

[CMSchoff]

Hey everyone! My name is Chris. I have an issue with my 1990 300zx NA and any help would be appreciated. When I bought the car, it ran great with the exception of the spark plugs being a little worn out. (Replaced them and the car ran PERFECT) Anyways, recently while driving the car it will run fine and then after a little while I go to accelerate and it wont speed up...just stays where its at or starts slowing down while sounding like its going to blow up or something. (Gets super loud too) But if I push the clutch in and shut the car off for a few seconds while driving and start it back up, it runs fine for a while. (That's the only way I was able to get it to run at full power again to get to work) I've replaced the TPS and MAF already. Anybody have any ideas of what it could be? Thanks! -Chris

[Destrto]

When you say it gets real loud, do you mean that it revs up, like the clutch is engaged? How do you replicate the issue? Is it while in any certain gear, any particular speed, does it only do it after the car has warmed up?

[CMSchoff]

Almost like a misfire type of sound. I drove my Z the other day and as long as I don't push the throttle more than half way the whole time driving, its fine. If I have to use more than that and speed up is when it happens. But when I first start the car its fine...it takes about 10 mins of driving for it to happen...not when I push the clutch in or anything...just when I push the throttle at least half way after driving the car for a little while. Then like I said, if I shut the car off and start it right back up its fine....but within a few minutes it will do it again.

[CMSchoff]

BUMP

Still yet to figure this out.

[amc49]

Could be a fuel pressure issue of some type, note it gets worse with more demand for power...................

[itsa300zx]

Hey everyone! My name is Chris. I have an issue with my 1990 300zx NA and any help would be appreciated. When I bought the car, it ran great with the exception of the spark plugs being a little worn out. (Replaced them and the car ran PERFECT) Anyways, recently while driving the car it will run fine and then after a little while I go to accelerate and it wont speed up...just stays where its at or starts slowing down while sounding like its going to blow up or something. (Gets super loud too) But if I push the clutch in and shut the car off for a few seconds while driving and start it back up, it runs fine for a while. (That's the only way I was able to get it to run at full power again to get to work) I've replaced the TPS and MAF already. Anybody have any ideas of what it could be? Thanks! -Chris

If the car ran great when you bought the car, why did you change the plugs?

If the car started to run poor after the changed plugs I would look at them again.

What plugs did you put it? OEM NGK or some after market brand.

[centralcoaster33]

Just a thought, but have you checked the voltage/ resistance of your throttle position sensor? It might be out of spec, sending incorrect data to the ECU and maybe the change in function is due to the shift from open to closed loop programming? I think the open to closed loop thing is triggered by the engine temp (ie, when it thinks it's nice and warmed up). You can check the FSM for more details of course.

[amc49]

The TPS itself can signal to go to open loop when the ECM picks up a wild swing on it demanding max acceleration, the TPS will be beyond its' normal slow sedate driving position. I wouldn't say it's TPS though as they commonly fault at idle or just off it because that is where they spend most time and the carbon strip then tends to wear the most there. Of course, anybody messing with it always has the ability to scrap one from misuse. The car shouldn't die at the difference in TPS to make open or closed loop anyway as the two aren't that different, closed loop just being leaner. And the ECM should recognize a faulty TPS signal to sub a past good running history reference in there to help out.

I'd be at the very least checking fuel filter if there is a remote one on the car.