Hi all,

Just bought a j spec 300zx tt and iv'e got a problem with the boost.

The car only boosts to 6psi.

I ran a diagnostics check and it came back code 55 all ok.

Can it still run in safety mode with no error codes

After a good thrash the car gets very hot with steam/smoke coming from the back of the engine with a burning smell.

Do i have a boost leak so the turbos getting hot working overtime

Cheers...steve...

hi mate and welcome to the club.

sorry to hear your Z isnt functioning as it should. As far as i know [and i prepare to stand corrected] your Z will not go into safety boost if youve got a 55 [unless the engine's cold i think]

when you say very hot, does the temp. gauge go above half-way?

burning smell - is it rubber? clutch? oil? hot water?

have you visually inspected the large pipes at the front of the engine bay? the standard rubber ones are prone to perish/crack around the jubilee clips and lose a little boost.

try your temp connector at the front of the car, if the ecu thinks its still cold your stay in safe boost

Hi mate,yeah the burning smell is like hot rubber if that makes any sense.

the temp gauge stays halfway so its not actually overheating the cooling system just getting really hot under bonnet

cheers...steve

hi ,could you tell me where the temp connector is sorry im new to this model...thanks

front of the engine with yellow connector IIRC, also the loom & connector to the sensor can give problems.

 

where in kent are you bud? :)

Check the stock boost solenoids are connected ;) Black connectors down each side of the engine.. If the car had a boost controller fitted previously, then these would have been disconnected. Passenger side one is mounted on the turbo compressor outlet pipe, drivers side on the bracket on the side of the plenum...

http://300zx.co.uk/forums/showthread.php?t=26120

thanks guys,

I'm in maidstone Paul not too far from you..

I did check the solenoids well the passenger side at least and they seem to be connected up ok..

Dont know if this has anything to do with it but there is a couple of solenoid looking things that have some boost/vacuum hoses that are disconnected and one of them has a bolt screwed in it to block it off..The solenoids are at the far left hand back corner as you look in the engine bay..cheers...steve

Those solenoids are for the egr/aivs so nothing to do with boost. Just one thought, how are you measuring the boost? Aftermarket guage?

yeah i used aftermarket gauge connected to the crossover rail between the two plenums,hope thats right place to connect it...cheers ...steve

Yeah thats the right place. Time to check the plumbing.... You could do with another car to check the pipework against really.

I've noticed that the 2 boost hoses that attach to the throttle bodies near the intercooler end of the hose and directly underneath it there is a pipe that possibly should have a vacuum hose attached to it but mine is just the open ended pipe.The dump valves were replaced by the previous owner for aftermarket ones on an alloy pipe,does it matter that these pipes are not blocked off....cheers guys....steve

Got any pics? Sounds like thats your problem area

I've got a mates car with a very similar problem, 6psi all the time, it had a code 34 but we bypassed the det sensor and now all is ok in that department, but still 6psi allbeit much quicker than before. Wastegate solenoids seem connected. With 1.2mm jets in, boost reaches 8psi but drops away to 6 at higher revs.

Thanks andy...i haven't a clue how to get pictures onto the computer i'll have to get the missus to show me...i'll try and describe the set up...the dump valves are chrome and sit on a cast alloy pipe shaped like a Y with orange/red hose connectors i think there called sequential something or other...the place i noticed the open ended vacuum pipes with no rubber hose on them was right under the boost pipe near where it goes into the intercooler,one of them is metal and quite long,the other is white plastic?..maybe i should try blocking these off...cheers...steve

wellcome dude! i will get that car fully check out,for a piece if mind..goodluck

Welcome, Just thought i'd better let you know from the little experience i've had with my j-spec tt you cannot trust the temp guage. My car boiled bigtime when i was bringing it home due to an ill fitting rad cap ( i think) and my temp gauge did not move from just above the halfway point. The only reason i new it was boilling was because i had water blowing out of the cap on the header tank and out the side of the bonnet. Now i have a blown head gasket. :( Good luck with it dude, i hope you didn't by aload of problems like me.

Really need a picture to be honest Steve. After 16 odd years most of these cars have had mods added then removed then others added etc so its hard to tell. One way of telling if it needs blanking would be to put your finger on the end of it with the engine running. If it sucks your finger on then its causing a vacuum leak - find the hose its supposed to go to...