This will be difficult to explain but here goes.

 

The zed is running well, it idles fine, is smooth and pulls well on acceleration, but I have this small issue when driving at a constant speed.

 

You feel the car ever so slightly bouncing in the revs, which manifests itself as a small rhythmic vibration in the cab (Steady!).

Its most noticeable when you are in a higher gear and often when cruising up an incline.

 

It only happens when the car is in gear, and stops instantly if you take it out of gear and coast, so I know its engine related rather than the drive train or wheels. Its like something isn’t controlling the revs properly and is bouncing on and off, and like I say this is when you are trying to maintain a steady speed.

 

Any thoughts?

 

Thanks

I have this, feels like its pulsing. Mine does it when I'm driving at 30 In 3rd gear.

Yes pulsing, thats a good way of explaining it.

Anyone?

what have you done to diagnose or solve the issue?

Only just started noticing it, wanted to get some suggestions before I start.

Ah, I see….

Well to me it sounds like something no too bad and may just be something simple like a bad connection or similar.

 

I would start with checking all the electrical connections in the engine bay (including the batter) hake sure they aren’t loose or corrodes.

Disconnecting some of them is a bit of a pain but worth it if they are at fault.

Be careful and take your time as the metal clips are a bit fiddly, if you are too rough you could damage connectors and that isn’t any help.

Make sure you check the MAF, CAS, PTU & TPS connectors. (I’d be going straight for the CAS first).

 

Check the air filter is clean and make sure your plugs are good.

Check fuel filter and if you can fuel pressure.

Check for leaks on the fuel rail.

Make sure the TPS is calibrated right and check the timing with a timing light.

The Throttle Bodies can also be checked and adjusted to be in sync.

You can also check the resistance on the injectors and the coil packs.

If you’re keen enough you could even take the CAS out and give it a clean (make sure you find a guide on it first, and be careful)

 

A full diagnostic with Conzult could also help narrow down any issues (there might be someone close to you that can help with that).

 

At the very least this work will rule out a heap of things.

 

Best of luck

and....

 

Jeff did a write up on TB calibration and there are heaps of other tech info on the site (in the tech section)..

 

Other tech sites are:

http://z32.wikispaces.com/

http://www.pexcom.com.au/z32cms/e107_plugins/content/content.php?cat.8

http://www.twinturbo.net/nissan/300zx/tech/tech.aspx

http://www.nicoclub.com/nissan-technical-articles#300zx

http://s95014253.onlinehome.us/63104/index.html

Thanks medalion Man. So it could be virtually anything then!

Thanks medalion Man. So it could be virtually anything then!

Typical 300zx :) lol

Thanks medalion Man. So it could be virtually anything then!

 

 

LOL.. the truth is I don't know.. :)

 

but I do know that since the issue is just very slight it is most likely something "not very wrong".

 

I can't say I've heard of that issue before and since you don't have a Conzult (nisture or whatever) readout on the car, it's hard to point to anything in particular.

 

So checking all those things will ensure that they are not the cause (and again, worth doing anyway, that will keep you ahead of any related issues).

 

there may be someone who has had that exact same issue and found the exact cause... but unless you do the checks and fixes one by one and then drive the car again it's hard to tell what exactly fixed it.

 

the stuff I've posted is the best first point of action as it cost little... and I know only too well that id you chase a problem by replacing comments it will cost you a packet.

 

:)