Rattling at higher RPM's

[AndysPlit]

...For years my Z seems to make a rattling sound somewhere in the engine bay. It usually happens whenever I floor it at high RPM's (approx. 4000 & above). Sometimes I'll see a cloud of white smoke too when I rev the motor high.

I know the white smoke could be a sign of worn piston rings. What about the rattling?

....I also read some older threads about the rattling. I don't think my car is pinging, but perhaps the valves are out of adjustment? As for the white smoke, my head gasket is fine.

[240ZX]

Andy,

You've not included very much information, regarding your rattle noise. Any reply would be a SWAG at best!

Tom

[AndysPlit]

Arg....I know. I suppose at this point it could be many different issues based on the info provided.

Ummm....what other info would be helpful?

[zbane]

Does the sound only occur when you are driving, or can you replicate in in neutral? If so, perhaps you can rev it up from the engine bay and better figure where the noise is coming from.

I would assume that you have checked every little thing that can come loose: air filter box, fuel rail, the plate that holds on the AFM, manifolds, fan shroud, radiator, etc.

And, yes, those are just some WAG's.

[AndysPlit]

Does the sound only occur when you are driving, or can you replicate in in neutral? If so, perhaps you can rev it up from the engine bay and better figure where the noise is coming from.

I would assume that you have checked every little thing that can come loose: air filter box, fuel rail, the plate that holds on the AFM, manifolds, fan shroud, radiator, etc.

And, yes, those are just some WAG's.

....I will check to see if I can replicate the rattling in nuetral. As far as I know, no. I'll double check if any parts are loose. I'll return to this thread with my results. Thanks!

[beandip]

A couple of questions, Is this a injected or carbed engine? What Ignition is in use and what advance is it set at? If this is a manual trans Z , if you put the trans in 4 gear and driving at about 1500 to 1800 rpm. floor it and see if you hear the noise then. Are you using regular or mid range or premium gas? Has there been any mods done to the engine or is it bone stock. Because of the smoke, it makes me suspect predetonation, pinging. If this is the cause you could either retard the spark or use higher octane fuel. Let us know what you find. Gary

[AndysPlit]

A couple of questions, Is this a injected or carbed engine? What Ignition is in use and what advance is it set at? If this is a manual trans Z , if you put the trans in 4 gear and driving at about 1500 to 1800 rpm. floor it and see if you hear the noise then. Are you using regular or mid range or premium gas? Has there been any mods done to the engine or is it bone stock. Because of the smoke, it makes me suspect predetonation, pinging. If this is the cause you could either retard the spark or use higher octane fuel. Let us know what you find. Gary

Gary: This a bone stock engine with 300,000 miles on it. It is injected with a 5 speed manual tranny. I use 87 octane gasoline. Hope this helps.

[sblake01]

This a bone stock engine with 300,000 miles on it.......

I think the answers to most of your questions lie in that statement. You can adjust the vavles but I doubt you be able to stop the smoke and rattling w/o refreshing the rings, valve guides, bearings........

[AndysPlit]

I think the answers to most of your questions lie in that statement. You can adjust the vavles but I doubt you be able to stop the smoke and rattling w/o refreshing the rings, valve guides, bearings........

Right, in other words I'll be looking into a rebuild down the road. Mmmm....I better start saving up.

Yesterday I did rev the engine in nuetral. No rattling. It just seems to happen when I floor it in gear. I think my engine is getting tired.

[xray]

Compression check? Leakdown test? Those results will tell you about ring condition, head gasket, valve condition etc. Have you checked/adjusted the valves?

[AndysPlit]

Compression check? Leakdown test? Those results will tell you about ring condition, head gasket, valve condition etc. Have you checked/adjusted the valves?

The valves are probably out of adjustment. Judging from the mileage since last time, I would say they are due.

I appreciate the help. But, I am aware that some of this is difficult to troubleshoot over the internet.

[biddljj]

What about a broken motor mount causing the exhaust system to hit something ?

zdisease