I bought my import 300ZX TT from Hallmarks in Thatcham about 6 weeks ago and have serious petrol consumption problems. Hallmarks have been great but just can't trace the problem. The Hallmarks tester shows that the emmissions are fine. I have tried running the car with a light foot (no turbo boost all week!!) and I still only get 12 mpg. The only

engine problem I have experienced is when pulling away from stop the revs drop from 1000rpm to 500 and it nearly or actually cuts out. Any help would be appreciated.

 

If emissions are OK then my first suggestion would be for fuel leaks rather than too much being burned.

 

The fuel hoses under the bonnet do get brittle with the amount of heat under the bonnet and it's very common to smell petrol when the car and weather is cold (tons of us have this problem). I guess if that got worse it might become a leak.

 

Or, more likely, a leak from the tank / fuel lines ?

 

Needless to say, quite important one to spot if it IS that.

 

Struggling to think of anything else if emissions are fine. Perhaps a Nissan Consult might spot something ?

 

Dave

 

Matthew, have the O2-sensors, fuel-regulator and fuel-damper checked.

The o2-sensors generally last 70000 miles, before they become dodgy.

Bad/old fuel-regulator & damper are known to have a very negative effect on fuel-consumption also..

 

Hope this helps,

Eric

 

My Fuel Pressure Regulator is known to be bad (leaking) and fuel economy is crap. Worth checking...

 

I'm gettin 18 -20mpg Is that good then?

 

Also get a petrol smell when cold but cant find any wet bits.

 

Willie

 

Willie,

 

Try checking under the top plate (the plastic one). I think it has 4 allen bolts securing it down. I had a bad fuel smell when cold and it was coming from the return feed on the fuel pressure regulator - the clamp had come loose! The best technique to find fuel leaks is to dry off the areas you suspect, and then give them a light coating of talc - you can see it dead easy when there's a leak this way!

 

One other point - fuel leaks always show up best when the engine is cold.

 

Andy

 

Thanks a lot for everyones help on this.... at least I've got some things to check out now!! cheers, Matt

 

I find that the best way to find a fuel leak is with a lighted match- you can't fail!

Dave ;o)

 

Dave, you forget to mention that it's best to do this at arms length ;-)

 

and under the supervision of a responsible adult....

 

Or......get your bestest mate with the longest arms in history who is the responsible adult.....

 

....To light the match and do doggy impressions...

 

 

WOOF........

 

:o)

 

Matty.

 

 

 

I just had mine overhauled and it had some cracked fuel lines, this was leaking petrol ever so slighlty so it might well be that but more severe, I get about 20 - 22 mpg on my 300zx Auto 2+2 Twin Turbo Jap import. Think you cant ask for more than that really, mmm, thirsty honey !!!

 

I had the same leak as Andy on the fuel regulator at the top right of the engine.

It was pretty well hidden on the pipe under the regulator. The pipe had perished and split around the jubilee clip.

Took me ages to find until it got really bad. Fuel evaporates quickly on a warm engine so use the talc trick. It's a pain in the arse to change as you have three very short pipes to force on at different angles.

Could be a common fault...