Noise/RPM question for '84 300ZX

[tortribune]

So I'm having some noise and RPM issues.

To address the noise issue. Lately, when I am driving my car, it makes a grinding noise (almost like when you grind the gear) while accelerating and before the gear is switched. It only lasts a few seconds, but it happens almost every time before the gear is switched. A friend of mine said muffler, but it sounds like it's coming from the engine.

Also, it makes a loud whining noise when held at a constant RPM (driving) but when the car is braked the noise stops. A belt issue, maybe? Although, less then 5 months ago we replaced the belts and it ran fine until a few weeks ago.

The RPM issue is, when the car is started is sometimes runs at a high RPM (12-13) or an extremely low RPM (5ish, almost to the point of stalling out and it shakes like it's going to, so I'll give it some gas and hold the RPM's at a constant until I am moving.) I thought it might be a heat problem or a starter problem, so I was looking at getting either a new starter or a heat wrap or both.

Any suggestions would be great!

Thanks,Dana

[evildky]

a "whining" noise I'd suspect the trans or the diff

[Perrenial Badass]

The sound issue... sounds... like it is the transmission. Next time it makes the sound, press in the clutch (so it returns the engine to idle) while still moving. If it stops making the sound than it is most likely from the clutch forward. If not, it probably is in the transmission or diff. If the noise worsens, it may be the clutch or a throwout bearing and such.

As for the idle issues... how old is the CHTS on your car? Chances are that it is bad. Replace that corroded sensor with a new one and watch as many of your idle issues go away. You may also have a bad vaccuum leak somewhere. As for the high idle, IDK what might be causing that. But I'd be willing to put some money on it being the CHTS's fault, as it tends to have some funky side effects when it goes bad.

And just for the hell of it... check the EGR to see if it is working. You may have a vaccuum leak out of that. It even has a short hose under it that likes to crack like hell. Do as such:...and if it idles right, then this needs to be "replaced". I'd just remove it and block off the holes on the plenium, but to each his own. If it doesn't change anything, then chances are it's something else.

[tortribune]

Awesome.

I'll have a look and see if your suggestions fix the problem.

I know a year or so ago, the sensor was replaced (by some mechanics in a small town that I was stranded in, lol), but it could be a bad part.

I can tell you for sure that while the car is still rolling and my foot is on the clutch, the noise stops. The first time it made that noise it freaked me out, and my automatic responce was to press in the clutch.

Anyway, thanks for the help, and I'll post back and let ya'll know how it turned out!

[Pharaohabq]

yeah, okay, so that kind of sounds like it's something in the clutch. does it still make noise when it's out of gear, and you rev the engine? and then still when you push in the clutch and it's out of gear still...? Phar

[michaelp]

S

The sound issue... sounds... like it is the transmission. Next time it makes the sound, press in the clutch (so it returns the engine to idle) while still moving. If it stops making the sound than it is most likely from the clutch forward. If not, it probably is in the transmission or diff. If the noise worsens, it may be the clutch or a throwout bearing and such.

As for the idle issues... how old is the CHTS on your car? Chances are that it is bad. Replace that corroded sensor with a new one and watch as many of your idle issues go away. You may also have a bad vaccuum leak somewhere. As for the high idle, IDK what might be causing that. But I'd be willing to put some money on it being the CHTS's fault, as it tends to have some funky side effects when it goes bad.

And just for the hell of it... check the EGR to see if it is working. You may have a vaccuum leak out of that. It even has a short hose under it that likes to crack like hell. Do as such:...and if it idles right, then this needs to be "replaced". I'd just remove it and block off the holes on the plenium, but to each his own. If it doesn't change anything, then chances are it's something else.

Stealing my picture...b**ch :P j/k