Help. 300zx TT stumbles hard when in positive boost

[1990TTZ]

Ok this is my first post to on this forum or any Z forum so thanks for any help it is all greatly appreciated as i have used much advice from this site just from reading through it.
So here is my issue just installed a used jdm engine and a gt600r turbo kit in the Z the engine first started great no bad rattles smoke etc it ran great runs but since i put it together 3 weeks ago im having a intermittent issue but it seems its sticking around now and getting worse as soon as i begin to build boost like at 0psi and up the engine stumbles feels like its loosing a cylinder or two at this time so i did normal boost leak test fixed sum leakes seemed to pull fine fow a few minutes and started again so i checked codes and got a det code 34, so i cleared and started car and let idle 5 min or so and 34 again so i swapped det sensor with one laying around and no more code. So after several boost leak test and timing test and testing ptu cleaning both Maf i still have the issue so i read about cas going out so swapped with the one that was on my old engine and wala ran great all afternoon me and a buddy zedded back country roads for about 50miles an sometimes running around 130mph. I did notice a slight breakup around 6k rpm during like a hard 2nd and 3 gear pull but that was it. Next day me and my gf went to go out and she was excited cuz i told her it was fixed now and boom as soon as no vaccume and boost began stumble stumble ran like crap. The car will run great without a load like in neutral 7500rpm clean and it runs great anywhere if not in boost. The turbos are spooling great both are working and itll pull 10-14psi quick where ever i have it set itll also take off good underboost in 1st gear like if i go to roast the back tire itll spool and blow the tires off also breaking up around 6k rpm. I also today pulled the timing belt back off and retimed it thinking it was off a tooth put back together and still doing it im really pissed at this point new turbos, engine, southbend clutch, fidanza light flywheel and have only got to actually feel the power like one or two evenings. Before all this it was a high 11- low 12sec 5speed z. Help i need my ride back.

[AZhitman]

Welcome aboard!

A few things to check out (and apologies if you've already been down this road):

hesitates-and-stumbles-on-acceleration-t507739.html
hesitation-stutter-loss-of-power-and-ba ... 28213.html
1990-300zx-na-hesitation-t475118.html
http://www.zhome.com/ZCMnL/PICS/hesitat ... ation.html

[evildky]

I'd personally look first at fuel pressure, the pump might be on it's way out and cant build the needed pressure once the FPR starts raising the line pressure. My other suggestion would be to look at the mas.

[1990TTZ]

Ok i got off work a little bit ago and did the fuel pressure test has exactly 37 idle with fpr hooked up and like 43.5 with it unconnected i drove around with gauge zip tied to wiper. As i gradually give it throttle pressure and boost rise accordingly if keep it under half throttle i can build full boost ( that i have it set to 10 psi for now) an run it through the rpm with no stumble as soon as i go to floor it it stumbles badly. I did notice fuel pressure spike from like 50 to 62 when in between .55 to .70 kg boost. I have also cleaned both mas air flow meters too i guess i should test them according to the service manual. Do guys think i could have coincidentally had 2 cas on verge of failure because it did run the best. For an afternoon when i put the one off my old engine on it ? Whats proper ohm test for this bc both cas click all coils and injectors like supposed to??

[AZhitman]

Dumb question, but are you running a BOV?

[1990TTZ]

Yes bov, 555cc injectors, egr delete, pretty much every other delete in the engine bay, dual mas air intake ,massive smic, catless down pipes, z1 chip ecu straight 3" exhaust, apexi avcr boost controller. It never acted like this with the old engine in the car ever
The only thing changed is engine and larger turbos

[1990TTZ]

So this evening i was able to do a power balance test and confirms running on all 6 cylinders.checked sum injectors and mas air meters this what i got

Pass side. Injector
(1) 11.3 ohm
(2) 11.4
(3) 11.4
Driver side injector
(1) 11.3
(2) 11.4
(3) 11.3

Both mas air meters
.53 volt cold engine off
Pass side mas .98 idle warm
Drive side 1.07idle warm
And both we 're .53 volt with key on engine off warm?

[AZhitman]

http://www.nicoclub.com/archives/z32-30 ... alves.html

[1990TTZ]

Yeah thanks for that info hitman but i bought car like owned it for a year blew old turbos which killed the engine. Yes it has always stumbled and came down to a idle funny after pushing clutch in because of this but im experience a stumble during positive boost when engine is under a load accelerating if i gradually let it build rpm and boost and keep throttle in Same position it wont break up itll pull all the way through rpm with full boost

[wisniaPl]

Hoe does a blown turbo damage engine?
Did it literally blown in pieces?

[1990TTZ]

It had bearings go out and sucked up pieces of the wheel and bearing

[1990TTZ]

How do i upload pics to the topic

[Ace2cool]

how-to-post-pictures-using-photobucket-t521110.html

[1990TTZ]

Ok and my next question is when i recieved this engine the cas was perfectly in the center and so was my other engine. I dressed the new eng up an put new timing belt etc. After i put engine in and started it and began checking timing it was running at 20 degrees perfect i has to adjust cas to pick up 15deg is this ok or does it signify timing belt off a tooth? Well i removed belt again and re timed it but my cas is still not centered to achieve 15deg am i still possibly off a tooth? all the cogs for all the cams count out correctly i cant get accurate count of check cogs from crank to driver side exh cam because lack of room. Im going to put it on dyno to test today do you guys think thatll tell me whats going on? All of you guys help is greatly appreciated thank you!

[Ace2cool]

If you were off a tooth on an interference engine, you'd be having a lot worse problems. Wherever the CAS needs to be to achieve 15*BTDC, is where it needs to be.

[1990TTZ]

Ok Problem solved!! So i took it to the local race shop with a dyno they strapped her down and did a pull at stock boost level. The guy checked ignition timing and a couple other things and felt like it was the spark plugs so he said he'll sell me plugs an put them in while leaving on dyno for a couple xtra bucks so i did he installed a new set of ngk v-power plugs heat range 7. Gapped to .025 .same setup in there nissan race cars and boom a clean even pull all the way through. My old plugs were clean gapped to .030 and just installed with new engine 500 miles ago.
Stock boost level made 305whp missing under boost
Stock boost level with new plugs 345whp
And at 13psi. Was 385whp he said every thing else was perfect and was safe to turn it up a couple lbs. And with sum engine management , race gas and injectors he said well play with try to get me around 550-600whp he feels comfortable with it making that much im so happy to b zedding again haha hope this can help someone else out too.

[NolimitZ32]

What turbos do you have and what dyno is at this shop?

[1990TTZ]

Ive got the gt600r kit from z1 the shop has a dyno jet

[wisniaPl]

How do those compare to gt28?
Glad.it was.only.sparkplugs

[1990TTZ]

I think gt28 is the same turbo except z1 installs custom actuator brackets so they properly fit. They also machine the compressor housing and put a large o-ring so that has a less chance of leaking at compressor housing. I put these turbos on a engine when the engine was still in the car. It is possible but alot easier if you pull the engine. But gettin down to it i love these turbos boost comes on strong even low end. They feel slightly less laggy than stock and they sound awesome they whistle loud when spooling and through my full straight exhaust they sound sweet too.
Also you can minimize lag with these turbos with an apexi avcr boost controller by adjusting the duty cycle up for lower rpm ranges. Use the replayable graph and do a couple 2nd 3rd 4th gear pulls and watch your boost vs rpm and adjust duty cycle according ive got my lag down so low itll slightly burn tires when shifting in 3rd while getting down on it.

[wisniaPl]

so basically same as gt28r but better fitment

[BLOODREDZ]

how much did all the upgrades cost you??

[1990TTZ]

Yes the 600 kit from z1 is like the 28r but z1 machined compressor housing to fit a o-ring for a better seal.

As far as upgrades and cost i bought the car running and driving. I traded a 2007 honda trx450r that i paid $1800 for the car already had the 2.5" intake tubing, massive godspeed intercoolers dual (smic), 555injectors, full z1 exhaust stainless straight pipes, dual mas air translator, dual mas air meters. And apexi avcr controller. I raped it for about 4 mos daily and drag strip every weekend untill it chucked lol on stock turbos with all other upgrades and 18-20psi boost car ran high 7s in 1/8 mile and low 12s almost 11s in 1/4 mile. I have now spent 3,000$ on turbos downpipes and gaskets and accessories. $1000 on a fidanza flywheel and southbend stage3 endurance clutch, and 1,200$ on a jdm engine with roughly 60k on it (i think it has about that) timing cover shows timing replacement at 44k miles and engine looked fresh and runs like beast it now is at 345whp 10psi and 385whp at 13psi good enough for the street haha i have about $6800 in the whole car

[BLOODREDZ]

Did you do all the work yourself?

[1990TTZ]

Yes i did. I am a well self trained mechanic especially on older carbed engines and old skool rides, dirt bikes and atvs etc. And am a heavy truck technition of 5yrs. And Only 24 haha. But the engine removal and installation is straight up simple i read peoples tragic stories of how tight and difficult it was. Wrong just do it youll b surprised how simple it is. And it is doable to replace turbos in the car but not worth it i repeat not worth it lol . I have done it b4. Just pull the engine

[BLOODREDZ]

lol i will keep that in mind. tho i am not a mechanic ,but i would like to become one... I'm not afraid to work on my own stuff tho if given the right instruction! Would you say a Z32 TT is a bad car to teach myself how to work on?

[evildky]

Z32 isn't overly complex it's just terribly packaged. Parts are expensive and some can be hard to come by.

[BLOODREDZ]

Thanks for your honesty! Proud new Z owner here