Ouch :(

 

I'm having trouble with the Z: coming back from Manchester to Nottingham last week, it cuts out in traffic (maybe half an hour after setting off) and won't start for about 10mins. Starts, runs fine, drives about 200yds and cuts out again. I leave it for longer, start it up, run it round a side road to check it's not going to cut out again, and then head off on my way. Maybe 20mins later it does the same thing again, but on an open road. Again, I start it (after about 5mins), leave it to idle a while, and it just dies. This goes on a couple more times before I give up & call the RAC. By the time they get there, of course it starts fine, bloke can't find anything wrong with it, and suggests maybe it is something to do with the ignition. He says he'll follow me down the road for a couple of miles to check it doesn't happen again. It doesn't, so I pull over to tell him it seems sorted. Then it won't start again, and stays that way resolutely for the 20mins or so it takes a recovery vehicle to turn up & drag it to the nearest garage.

 

Next day, when I turn up with a trailer, it's starting fine again. But I don't trust it to get me further than however long it takes to warm up (hence I'm not sure it will make it to Jeff's in one go).

 

What happens when it cuts out? It just cuts out! If I put it back into gear to try and restart it on the roll, it runs, but there's NO power (I mean, the revs just keep dropping, though it's not kangerooing or anything). As soon as I take it out of gear, it stalls. While rolling to a halt in gear, it sometimes makes loud popping noises, and at some point it's blown a hole in the swan-neck of the exhaust.

 

Searching through the forum, it sounds like it might be PTU trouble (I only did a quick search, because my home ISP is messed up, so I'm at the local library :S). RAC man said it sounded like an ignition problem, dodgy wiring that screws up when it gets warm. I know nothing :/

 

He also said it might be relevant that for the last week or two, it's been unhappy in rain - a little dampness & it runs rough, with loss of power at low revs (say up to about 2-2.5k rpm).

 

Advice, anyone? Like I said, I'd like to take it up to Jeff's, but I'm not sure if I can trust it to get me there (about 45mins drive). Is there anyone local (by which I mean Nottingham) with diagnosis software, or confidence enough to do the ECU test thingy?

 

Thanks for any suggestions (oh, and for advice on the best thing to do with the exhaust now - weld or replace? Stainless or no? How expensive will such a short section be?).

 

b.

YOu may have more than one problem, but it sounds VERY VERY much like the PTU to me. Might be worth taking it off and calening all the connections. If that doesn't fix it then buy one of the new uprated ones from Courtesy in ths US.

OK, now I've checked the most excellent AndyP tech info site, and seen where the PTU actually is. Immediately I recognise it as a spot RAC man pointed out for being a mess of wiring held on with strip-wire. Jeff did a timing belt change a few months back, so I figured it must've been moved about then...

 

Anyway, so a good first plan is to check it's still the pre-93 PTU (i.e. an aluminium one?), take it completely off & clean the external connections to it? OK, I'll see how feasible that looks with my big fat hands. Thanks!

 

What are the symptoms that make you think I might have multiple problems? The dodgy rain behaviour? I figured that was a separate issue as well, but possibly RAC man got locked into the idea it was ignition trouble, whether it be from arcing or heating up. I think he was talking about the "ignition crank sensor"..? I'll have to look that up too ;)

 

Thanks again!

 

b.

Hi,

Just want to say thank you very much for taking the time to do a search before asking a question. If only more people would do the same :D.

 

Deffo sounds like the PTU to me, one of the most common problems on the 300zx.

 

Not sure why it would have blown a hole in the zorst though

:confused: .

 

How bad is the hole ?.

Definately agreed it sounds like the PTU but second thing to check would be the coolant temp sensor. The wiring to mine was naff to say the very least and it also gave the exact symptoms you have described; cutting out, not re-starting etc. I'm guessing that in my case, it wouldn't re-start as the ECU thinks the engine is/has over-heated and is allowing time for it to supposedly 'cool down'.

A good clean on both of these may just cure your problem. Good luck, let us know how you get on.

(There is a tell-tale sign if the temp sensor or wiring to it is faulty and thats if your little elec fan appears to be running all the time, if you're not sure then get on your hands and knees and look up through the front at the bottom)

Originally posted by smw1

Not sure why it would have blown a hole in the zorst though

:confused: .

 

How bad is the hole ?.

 

 

I dont know my exhaust gave out about 4 or 5 very large bangs and flames when the PTU packed in. The fuel obviously going down the exhust becuase there was no spark, and causing the combustion in the exhaust. Cant do it any good.

 

Stuart

Hmm, it's about the size of a ten pence piece, right after the kink in the pipe, with (I think) a couple of much smaller holes just after it. My bodgy mate says it's weldable... but this is a guy who regularly kills cars or mends them til they're undriveable :S To me the whole pipe looks a bit crumbly & past it... I have sexy big SS backboxes, and the front half of the exhaust looks fine, it's just these short sections that look rough :(

 

Anyway, RAC man said it's a problem with swan-necks - all the crud builds up at the kink, and one good pop will blow a hole out. I described the noises as "pops", but really they were a little more violent, just not enough to call a "bang", you know?

 

As for searching... I should've checked AndyP's site sooner too, but it feels so rushed trying to internet in the library - you never know when you're going to get chucked off :S I'm glad you're focussing on the positive aspects of my post, rather than the negative aspects of my incompetence and tendency to waffle.... heh ;)

 

Ah, james300: Thanks for the suggestion :) Is the temp sensor you're talking about the one right at the front of the engine, in the centre? With the cold start thingy next to it? I noticed the fit between the plastic bits was a bit wobblier than I would have expected, but when I pointed it out to RAC man he wasn't interested.

Little fan? Not the big one? OK, I'll check it out. I know the temp gauge on the dashboard was acting normally, but that means nothing, right?

 

Thanks all! :D

 

Oh, and dammit, I keep forgetting to mention this is all on an NA, not a TT, just in case it makes a difference :S Heh, some of us can't afford *real* Zs :P

Originally posted by baby ice dog

Ah, james300: Thanks for the suggestion :) Is the temp sensor you're talking about the one right at the front of the engine, in the centre? With the cold start thingy next to it? I noticed the fit between the plastic bits was a bit wobblier than I would have expected, but when I pointed it out to RAC man he wasn't interested.

Little fan? Not the big one? OK, I'll check it out. I know the temp gauge on the dashboard was acting normally, but that means nothing, right?

 

Yes, the temp sensor is right in the middle at the front with a smaller sensor to the right hand side, a couple of inches away. My actual sensor was fine, it was just the oxidised wiring and connections to it. (this is just my own opinion but I found a little dip in the revs before they increased was also due to this coolant sensor)

 

Not the big fan, that will always spin as it on a viscous coupling to the engine. It is the much smaller fan nearer the front of the car, tbh I don't even know if the na's have them, I would've thought so! The temp gauge on the dash would behave normally, you're right, so this is no indication if the sensor is faulty.

 

But as I said, this is a secondary check after the PTU.

OK, good info. Again, AndyP's site helps out and says there *is* an aux fan on the NA :)

 

I'll check the connections, reply if I can get my home ISP to work. Kids want puter now, must leave. Thanks!

I see you're in Nottingham, close by to Luke at the Z Centre, he is always worth a call and is really helpful. He used to be technical advisor to the Z Club I think. Does exhausts aswell!! :D ;)

Originally posted by james300

Definately agreed it sounds like the PTU but second thing to check would be the coolant temp sensor. The wiring to mine was naff to say the very least and it also gave the exact symptoms you have described

 

Just the wiring on the temp sensor that's naff in your engine you say ? :D :D :D.

I'm gonna order a few additional injector and coil harnesses on my next call to courtesy, I'll order you one as well mate.

Originally posted by smw1

Just the wiring on the temp sensor that's naff in your engine you say ? :D :D :D.

I'm gonna order a few additional injector and coil harnesses on my next call to courtesy, I'll order you one as well mate.

 

No, didn't say 'just' the temp sensor wiring was naff! :D :D :D

 

One? 6 of each would be lovely mate! Seriously, are you ordering?

Ive been spending some time lately cleaning and my car is running better than ever. I want to clean the connections to the PTU, but where is it located?

 

Ray

Check the links for AndyP's site, where the tech info section has pics of the PTU. It's on the timing belt cover, a little box down on the driver's side, with a couple of fat wire bundles heading into it.

 

And back to my problem: I've noticed my PTU is black, not silver Al, but it has a '92 date on it. I've also noticed it's crammed into a gap between fairly inflexible ducts, so I'm not confident about removing it without dropping something important into the bay. Well, the suggestion to harrass Luke about it is a good one - I've exchanged posts with him once or twice, and he seems like a nice chap. Plus if I'm going to need an exhaust, this would be mutually beneficial ;)

 

As for the temp sensor: not got round to starting it up yet (was busy setting up this ISP and glueing skirting board), but I had a brief glance and noticed that the reason it was wobbly is that it's now missing that wire clip that should be holding the plastic bits together. Bugger, might be a factor, eh? And is there a simple way to clean the connectors, or do I just have to fold up some emery paper nice & tight to fit it in the tiny gap there is?

 

Well, thx everyone for your help :) I'll let you know what it turns out to be - right now I'm thinking about how to test it without just going for a ride until it cuts out in an awkward place :P

Originally posted by baby ice dog

I described the noises as "pops", but really they were a little more violent, just not enough to call a "bang", you know?

 

 

I know what you mean. Mine banged 2-3 times when my put just stopped working while I was at 4000+rpm.

 

Sounded like a starting pistol.

 

If your exhaust was already crumbling, that would be enough to blow the holes out of already weak and rusted parts, but I doubt to blow a hole in good metal

 

 

Stuart