My Z has deteriorated overnight. To follow on from my previous thread - basically from the start of this week she's been driving like sometimes she's on 5 cylinders. Once the engine warms up, she misfires a little and holds back a bit when I accelerate from low revs. She boosts ok, although now sometimes she'll judder a bit as the revs go above 4k. Don't appear to be symptoms of wet MAF as I've had that loads of times before (revs just cut under boost).

 

Anyways yesterday afternoon on the way back from work she started to buzz loudly whenever I took my foot off the throttle. The sound seemed to be coming from behind the dash, but I confirmed this morning that it's from the driver footwell.

 

I went out today with the hope of fixing the misfiring - I taped up a couple of cut/bare wires, pushed the coilpack plugs in firmly, checked the ECU temp sensor, the plug to the CAS and TPS, and had a general nose around the engine bay. I also taped up the connections to the PTU (which is relocated and exposed a little to the rain under my nose panel) and fired her up.

 

She idled ok for a couple of minutes, then as she warmed up the revs dropped to 650 and she started to struggle idling. She revs ok (but hesitates a bit), but if I rev her over 4k or so, once I take my foot off it'll drop and stall. No visible smoke from exhausts, although yesterday there would be a puff of dark grey smoke on overrun.

 

The LIGHTS warning light has started to come on which it never has before, and when I rev the engine, or switch the fans on, then off, there's a loud buzzing from the driver's footwell, around the fusebox area - like a failing solenoid perhaps. From cold, the LIGHTS light would flicker quickly 'in time' with the buzzing, but then it stays on.

 

Video is here:

 

Any ideas as I wonder if these symptoms are connected somehow...?

that sounds like a relay gone abit tits up ... your gonna have to start searching under dash/fuse box

There are relays mounted on the rear of the fuse box it could be one of them, it's not overly difficult to remove, remove the door sill, remove the plastic trim near the fuse box, remove the ancillary connectors of the side of the fuse box, 3x10mm bolts holding the fuse box in place, then it's a case of easing it out between the throttle pedal and the car body, remember to unplug as you go, you can't go wrong putting it back as most cables only go in the place they were intended, or they side pretty much where you would plug them in, there are a few connectors on the rear of the fuse box as well that need disconnecting

 

The light light on the dash comes on when you have a bulb out, so could be a sign something isn't right around that area at the rear of the fuse box, I'm pretty sure (not 100%) that some items share the same relays at the rear of the fuse box

 

If there are dodgy spelling mistakes in the above, it's because I'm using me iPad lol

I would get the fuse board out and see what condition the relays and tracks are like on the rear of it, sounds like an electrical short.

thanks folks - I'll take a look tomorrow :thumbup:

Right I'm nearly there with the fuse box - I ran the Z again and I'm 95% certain the buzzing is coming from behind the fuse box so after nearly breaking most bones in my neck and spine I've got it to the stage where everything's unplugged but I need to unclip the sockets from the edges of the fuse box - especially the three in the centre of the first pic - how the hell do these unlip? Do they come forwards or go backwards? I've got no strength or skin left in my fingers to try them any more!

 

Also, what the heck is the white box in the second picture - it's screwed to the body next to the fuse box?

the best way to get the fuse box out (because there are relays on the back of it) is to undo the accelerator pedal and the bonnet release.

 

if you can see the part number you could look it up here..

 

http://www.courtesyparts.com/300zx-parts-z32-1990-1996/genuine-nissan-parts/body-electrical/253-electrical-unit/-c-882_883_923_929.html

 

looks to me like the the timer control... (other side in the USA)

 

this one make it more clear for our cars... (UK)

 

http://nissan4u.com/parts/300zx/er_z32/1992_3/type_1/body_electrical/electrical_unit/illustration_1/

Edited September 15, 201213 yr by Medallion Man

thanks matey - I wonder what the Control Timer is for.

wipers (i think)

Hi Evoluzion3

I had the same problem not so long back, below is a copy of my exploits.

 

 

At last the little bu**er (fuse box) is out of the way. The piggy back connectors all come off in a forward direction,

The trick is to use a thin narrow bladed screwdriver (no more than 3mm wide) to prise the barb on the back of the connector away from the raised step on the fuse box side. This is done by inserting the screwdriver in from the front, (blade level to the base of the connector) and making sure you are under the barb. Then it is a matter of applying pressure as if you are trying to separate the connector from the box whilst at the same time pulling the connector forward. It took me a few attempts but once I had done one, the others were easy.

Now all I have to do is get at the pipe work by way of removing the soundproofing etc' and re connect the pipe.

Tcu ( Time control unit) controls intermittent wipers, dash light dimming and interior light delay if working

Hi Evoluzion3

I had the same problem not so long back, below is a copy of my exploits.

 

 

At last the little bu**er (fuse box) is out of the way. The piggy back connectors all come off in a forward direction,

The trick is to use a thin narrow bladed screwdriver (no more than 3mm wide) to prise the barb on the back of the connector away from the raised step on the fuse box side. This is done by inserting the screwdriver in from the front, (blade level to the base of the connector) and making sure you are under the barb. Then it is a matter of applying pressure as if you are trying to separate the connector from the box whilst at the same time pulling the connector forward. It took me a few attempts but once I had done one, the others were easy.

Now all I have to do is get at the pipe work by way of removing the soundproofing etc' and re connect the pipe.

 

Thanks RedWine that's just what I was looking for!

 

 

Tcu ( Time control unit) controls intermittent wipers, dash light dimming and interior light delay if working

 

Thanks Groover. The above are working, at first glance it looked like the white box should have some sort of fluid in!

Update on this - after largely being unable to test the relays due to the pins being so close together and probably frying one of them in my attempts, I left them with a local garage who eventually turned round and said they'd be unable to test them because they don't know what they do. I was under the impression you could run them through a 12v circuit and hear them click when you close the circuit, but I don't pretend to be an electrician!

 

So I have received 5 replacements, which I have swapped over and, after a couple of attempts to get the fuse box back in (I'm sure it's grown in size since I took it out!) I have got everything plugged back in. She started up ok but the buzzing's continued :rant: so it's the remaining relay that's at fault (the LC RLY one) - I've left the area as open as possible and thankfully this relay's closest to the near edge of the rear of the fuse box so I was able to put my finger on it and feel it buzzing.

 

I'm not sure what this relay does, however I'm getting the following symptoms which have all cropped up immediately since the relay started buzzing:

LIGHTS light on

Poor idling (~650rpm)

Stutter and stall when lifting off after high revs

Aircon doesn't come on at all now - the controls are responding (beep and light on pod) but no aircon

 

Hopefully these are all gremlins from the same source (I hope) so let's see what happens when I get the final relay swapped out...

Update on this - I received the LC RLY through yesterday (thanks dkboro121), plugged it in today and guess what...

 

...

 

still buzzing!!! it's definitely that relay, I can feel it buzzing when I place my finger on it (to get it to buzz I just push the throttle with my finger). When I remove the relay with the motor still running, no buzzing. So either, by sheer amazing coincidence, both my old one and the replacement have failed, or there's something fundamentally wrong with the fuse box itself?

 

The car still runs sluggish, about 650rpm and feels 'weak'. I've not taken it out for a drive, just let it idle for a few minutes while I've been swearing at it. This is both with and without the relay plugged in.

 

I did notice that there were a fair few drops of water around the fuse box area - it's the first time I've noticed this, probably by combination of leaving the trim around the fuse box off while I've been working on it, and the cold weather and ice no doubt melting and running down into that area. Perhaps the issue is water ingress, albeit I've never had this problem before (and it started a couple of months ago before the cold weather).

 

Any ideas anyone? :( I'll read up on Jeff's wet fuse box thread to get some pointers.

I could be barking up the wrong tree here guy's but one of you might have had something along these lines before. I work in the Aero industry and although cannot share this experience on a car, I've certainly had this fault on numerous aircraft electrical systems. These are not too different from a car over than it's 28 volts. The 2 common causes of a buzzing relay are either the voltage supply to the relay to throw the switch is decreasing or there is a voltage already on the switchable line, causing a stale mate situation. There is of course the Earthing side of the relay to keep in mind. I know this doesn't answer the question, but someone might recall a similar situation.

thanks Osty - not sure whether related but I noticed a white powdery residue around the clamp to the positive terminal where I have the maintenance charger attached.

have you checked all the earthing on main things like alternatior/engine block, ecu, battery, etc etc... its gotta be something common to all those things.

 

i think the white powder is commonive had it on my cars just a dab of grease will stop it happening

If you need a spare fuse box to try so as to eliminate the one you have , then I have one you could borrow.

In fact I think I have two. would be more than happy to post them out to you if you like.

Have u checked the outPUT OF THE BATTERY, maybe your looking to much to deep. any electrical problem i always start there and 90 % of the time its due to batt that has lost a cople cells, HEY JUST A THOUGHT/?

Thanks folks, esp. redwine :yes: . I've seen a few comments on the tinterweb that say it's a good idea to start with the battery - even if it appears to be functional. I've had battery drain issues for a long time now (i.e. a few years) - even across two different batteries, although one of them has now totally failed and blows a charger fuse when I attempt to recharge it. I'll do a few more sense checks and then consider buying a new battery. If there are still problems then I'll have to try and trace for any earthing issues, although lord knows where to start!

I too had a parasitic drain of 1.5 amps. Killed 2 batteries before I cured it. Turned out to be one of the white connectors near the fuse box in question. Like you mate, I had water ingress for quite some time. I resolved mine by opening up the connector itself only to find that green corrosion had built up to such a degree it had bridged across the internal connections causing a short. Once I had cleared this the drain had gone. Maybe you have a similar issue?

I narrowed mine down by placing a meter in series and one by one disconnected each connector until I found the culprit.

Hope that is of some help mate.

I think that's the bulb check relay. When it's chattering, is the charge warning lamp also flickering? If so then it points to an issue with the voltage sense line from the alternator. What is the voltage at the battery terminals when the engine is running? Does it remain stable as you rev? If you've dried off the fusebox then I'd be looking at alternator/wiring to it or battery.

 

Have a look at the workshop manual pages EL-7, EL-25 and EL-70 to see the wiring for this relay.

Any updates mate?

I had a uk zed i broke a while ago the main power wire and some of the other feeds in both the passenger and drivers footwell had corroded due to the T-tops leaking the drain tube runs right by the fuse box and wiring, I would really get the box out check and clean all the connections on the fuse box and all the connectors with a decent contact cleaner, clean you battery terminals as well. if this buzzing is coming on with the lights circuit id just check all the bulb connections as well for corrosion.

 

Also do you have dirt shields in the wings as water could get in through the loom as it enters the car there, if extra wires have been run there at some point in time. Hope some thing helps.

thanks for the continued suggestions everyone, they're all very valuable. she's been off the road since this problem started and tbh I can't be arsed to look into it until the weather warms up a little. I'll keep this thread updated with my failed attempts to fix it!

Another 'update': I went out and bought a brand new battery for her this morning. There were a couple of suggestions on the net that even though the battery manages to hold a charge (well, for a few days when not used) it could still be the battery that's at fault and causing gremlins in the system - the old battery has been in the Z for about 3 or 4 years and with a parasitic drain and being on maintenance charge fairly often I thought it might be worth replacing. £85 and a high-powered battery later and the buzzing is still there, lol. However to be fair to the old girl she fired up straight away and other than the ticking you get when you've not run the engine for 5 months she was fine. Topped the oil up, took her for some petrol (ticking stopped by now so that's good), then gave her a good blast along some country roads for half an hour and, apart from the buzzing and the feeling that she's not running quite right (like on 5 and a half cylinders), she still went like a b***ard! In a way I didn't want her to drive so well because I've been thinking about consolidating the Z and the Civic down to one car and have been thinking about calling it a day (or rather decade!) but that's for another thread. So basically, I'm still none the wiser but at least I've ruled out the old battery as the culprit.