Can anyone help me? My 260Z 2+2 has just started playing up this weekend. Infrequently, I seem to be losing power and the engine seems to judder. If I put my foot down it judders some more. The car does not stall and if I put it in neutral and increase the revs the engine reaches a peak way before the red line (I think as my tacho is not reliable). Each time I have done this the problem eventually seems to sort itself out for a while. I have a feeling it may be fuel related.

Yes, I have 'flat tops' but until this week they have been running well. Yesterday I scored an L26 complete with 5 speed and SU's for AUS$200 so the SU's will be transferred across later this week. Obviously I am hoping this will solve the problem but if anyone has any ideas I would be grateful.

Nigel Mulvey

Pristine Original 260Z 2+2 (Daily Driver)

240Z Project Car (Proposed)

Yeah I would suggest putting the round top SU's on your Z. Flat top carbs can behave like you were describing. When you do put the new carbs on, you might consider putting a new fuel filter on at the same time. A good tune up, cap, rotor and plugs could help as well. Do you still have the original ignition or have you gone to an electronic ignition? Something else to consider. Still have the manual fuel pump or have you converted to all electric? These are simple things but can make a big difference.

Almost sounds like vapor lock.Is it a bucking type judder?Were you sitting still a long time on a hot day?Was the fix to run it on the open road a while or just park it for a couple of hours? Daniel

Yeah, I thought vapour lock too...somebody's starving...

steve77

If it does it only after the engine warms up and not when it is cold, I would guess the water control valve is stuck open and over heating the carbs causing vapor lock.

Thanks guys. The vapour lock thing puzzles me though. It's not particularly hot here at the moment, in fact we've had some of the coolest days we've had in a long time. Now the car is misbehaving right from start up even after standing for many hours. It's also started spitting sparks I hope this isn't terminal. Any ideas?

Nigel Mulvey

Pristine 1974 260Z 2+2 (Running like **** at the moment)

240Z Project Car (Proposed)

Where is it spitting sparks from??

The exhaust.

Before you go off and start changing everything on the engine, address one very VERY common problem that plagues the Z cars with the mechanical distributor.

Go to your distributor, remove the cap. Look down below the advance plate, see any ball bearings rolling around loose? There should NOT be any. Disconnect the vacuum advance hose, either hook it up to a vacuum pump or just suck on it. Does the plate rotate smoothly AND return to it's prior position without hanging up and stuttering, then you're ok, but if it does NOT, and I'm guessing it won't, then your vacuum advance plate is shot.

This is a little plastic squirrel cage that holds several ball bearings that allow the distributor mechanism to move forward and return in response to the vacuum in the engine. When this isn't working properly, the vacuum advance is essentially gone. Now your timing is off by several degrees, and the worst thing is, that it isn't consistent, as a good throttle push will cause it to advance, but it won't be able to return, and then vibration WILL return it some, and then it will seem to get worse, then better, then not at all, then repeat over and over again.

Check this BEFORE you address all the other suggestions, as it will cause backfiring through the carbs, the exhaust, as well as limit power and then seem to disappear, only to begin again.

2¢

I tried blowing up the pipe to check the vacuum plate and all seems OK. I drove the car down to my mechanic's house in the dead of night to avoid the traffic I'd have to brave friving it in rush hour to his shop. He drove it last night and at least he experienced it playing up.

I should add that this all started after I had left his shop following a service. I turned round to take it back to him and it fixed itself, so I turned back for home and it started again this happened three times so I gave up and limped home in disgust.

Anyway, when my mechanic drove it down to his shop the following day, it was fine and has been ever since. He apparently blew some air through the fuel lines and all was OK, he emptied the fuel tank and the fuel was clean. He took it for a drive and along to a Zed Head colleague down the road (the guy who has sold me the other L6 with all the goodies) and he was baffled too.

So next week I am going to fit the SU's and the electronic distributor and keep my fingers crossed.

One final request for advice though, it was suggested by one person that I put about 30 litres of premium unleaded in the tank along with some injector cleaner which should clean out any blockages in the carbs. Any thoughts anyone? Sounds a little dubious to me.

I did of course mean I sucked up the vacuum pipe.

Having driven the car last weekend without incident, my wife took it out on Monday and it started playing up again. She managed to limp home and nearly got wiped out on a local busy roundabout. Her love affair with z's is rapidly fading.

I've done everything I can think of except change the carbies which I shall be doing this weekend (although I've got no transport to get to the spares shop to buy the gaskets I'm going to need - Catch 22:confused: ). If that doesn't do it I can't think what the problem is.

Check the fuel filters, one in the engine bay, and the one in the electric pump in the rear.

I bet your problem is there in the rear pump filter, esp. since it seemed to run better for a time after the fuel lines were cleaned.