Hi all, I hope someone can give me some pointers. I've got a fresh import Fairlady Z Twin turbo, manual gearbox. It has a running problem, symptoms as follows:

 

On the road it won't rev past 5,000rpm, but it will when not under load, eg. when stationary. It occasionally stalls. No warning lights come on and the ECU fault led flashes '55' when checked (I think that means no faults).

 

This is a car I'm fixing for someone else and unfortunately I don't have access to another similar one to swap bits so I'd like to know what order to attempt fixes in. I've changed the fuel filter (underbonnet one) as that was my first thought and I had a new one on the shelf. No difference.

 

Any ideas would be appereciated.

 

Thanks,

Andrew

sounds like your MAF/ AFM is possibly faulty bud , try a different one and see if that solves it . Try one of the breakers in the traders section. Also could be possibly a boost leak causing stalling , put a small amount of pressure in through the intake and see if u can hear any leaks/hissing.

 

Karl

Thanks Karl, I'll try and get an AFM tomorrow and will give it a try.

 

Regards,

Andrew

Firstly I'd try cleaning all the connectors you can find, PTU, TPS, MAF, injectors, coil packs, the list is rather long .............................

I've now swapped out the AFM with another one, no difference at all, still won't rev under load and occasionally stalls when it comes to a halt. I've also changed the timing belt, oil, air and fuel filters, checked a plug which didn't look old so I haven't changed the plugs. I suspect it's electrical as the cat heat light comes on occasionally suggesting there is unburnt fuel going through. It sailed through an emmissions test and there are still no fault codes.

 

Thanks for the help so far,

 

Andrew

seen this before twice and in both cases the problem was caused by the plugs.

Also in both cases the plugs looked fine, but problem went straight away after putting in new plugs.

 

if the problem becomes less severe after regapping the current (old) plugs to 0.9 - 0.8 mm it's 100% the plugs and they need to be replaced

 

also check if the correct plug type was used (should be NGK pfr6b-11c or 11b)

 

-Eric

Thanks Eric, I've now swapped the plugs (they were PFR6B-11) for new ones, no difference, still won't rev past 5k and idle drops when coming to a halt.

 

Andrew

Have you checked it with a conzult yet ?

Have you checked it with a conzult yet ?

 

Sorry, what's a 'conzult'?

Sorry, what's a 'conzult'?

 

 

Diagnostic software.

 

It could be your TPS. Throttle position sensor?

Will that tell me anything that the fault code check on the ecu doesn't? When I checked that it just showed '55' which is no faults found I believe.

so my z has the same problem and its not even close yo what you guys are thinking you have too take a closer look at things all of what you guys said was wrong would make the car faulty in other places too so what it really is is that you need a new fuel pump probably lines and injectors to be cleaned inspected and replaced also what happens is that the fuel pump on z's dont run at a constant 1 speed they spin faster the harder you push the throttle so at wot it sould have more psi than closed throttle so take a fuel pressure gauge and hook it up to your fuel lines then take the readings at several throttle positions closed half and fully open if is below specs the pump is bad another was to tell you pump might be wearing out is that it whines when you first turn the ignition on and will whine when you turn the engine off it whines when the engine is running also but its harder to hear because the engine is usally louder than the pump. if the pump is good check your fuell pressure regulator if thats good go down to the injectors a great site i use that explains this better is http://www.300zx.co.uk/cgi-bin/manual.cgi hope you fix it

Well, finally found the problem. The r/h intercooler had a split in the end. Thanks to all for your suggestions and to David at Rice Rocket for providing the parts very quickly.

Wow, do you know how it caused those symptoms then? Would that be like a normal boost leak? I just wondered why it stopped the car revving above 5k?

Also (not sure on this) doesn't a boost leak often make the car run lean? in which case what about the unburnt fuel you mentioned.

Just curious as its always good to learn new things. Dave

Ah i had to wait an extra two weeks for my ZX from the garage cos mine would not rev over 5000rpm. All the Conzaut readings were ok. So in order the fuel pump and filter was replaced. Then spark plugs, then lamba sensors. In the end it was found to be a leaky left intercooler.