hey guys i jus replaced all 6 of my injectors with stock sized aftermarket injectors. (venom from tlf performance)

The car is a 1992 TT 5-speed with 53,xxx original milesz1 motorsports intakeMegan Racing DP's + TP'sJDM Greddy Evolution style Cat-Back

While the plenum was off i threw on my Megan Racing Downpipes and Testpipes.

Now when i picked my car up the idle was very smooth and it drives 100 times better

however now when i get on the throttle my boost gauge settles at the second hashmark until about 5k then it goes to the 3rd hash. Before the installs boost would always settle at the 3rd hash starting at about 3,500rpms if i remember right.

any ideas what could cause this ive checked every vacuum hose under the hood. the car doesnt feel as quick low end, so i have to believe i have a boost leak... cause when i go to 5k i feel the power i think i should be seeing.

this is really the only problem. i was expecting big power gains with the downpipes and testpipes. but am disappointed im not having the boost consistancy i had before the install.

any input is appreciated

check all the pipes going to and from your turbos that you took off... often a boost leak on the upper plenum will not cause a seriously noticable difference when under power because almost all of the hoses on the top of the plenum are small. im not really sure as to the hash marsk you are referring to because the stock boost gauge is not very accurate. if you have a boost/vaccum gauge to hook up i woudl hook it up and find out soem real numbers. i would check all the clamps on teh pipes to the turbos the main intake ones can easily slip out of place... one of mine popped off once and i ran 7 pounds and i checked everywhere and i finally found it once i pulled off my 2 upper intake hoses. goodluck

i will check all my exhaust piping to make sure that is all sealed tight.

also i realized my car is taking longer than normal to turn over. like a have to hold the key for a few seconds before it fires up.

anyone know what my problem could be

Do a boost leak test. That's the only way to ensure there are no leaks.

*Boost is totally dependent upon load and engine performance. If the engine isn't producing proper power, or it's lagging it will affect the boost it can generate.

Zwicked wrote:Do a boost leak test. That's the only way to ensure there are no leaks.

*Boost is totally dependent upon load and engine performance. If the engine isn't producing proper power, or it's lagging it will affect the boost it can generate.

how do i go about it?

do these symptoms sound like a boost leak? or something else?

It could be a boost leak, bad injector ( I know they are new but Venom has the worst reputation) bad electrical connection, failed o2 etc...etc.

What upgrades do you have such as boost jets or boost controller and ECU upgrade?

If you really want to make sure it's running as good as it can:

1. run ECU diagnostics to make sure nothing obvious has failed.2. pull all electrical connectors and make sure none has corrosion (CAS, PTU, MAF, TPS, AAC, FICD, Air Reg, Injectors, CTS)3. test all of the above components to make sure they are in spec4. what plugs do you have? Stock is best gapped accordingly for mods5. boost leak test http://www.twinturbo.net/net/v...02104

...this might help too to know where to look http://www.thumper300zx.com/z3...e.htm

Zwicked wrote:It could be a boost leak, bad injector ( I know they are new but Venom has the worst reputation) bad electrical connection, failed o2 etc...etc.

What upgrades do you have such as boost jets or boost controller and ECU upgrade?

If you really want to make sure it's running as good as it can:

1. run ECU diagnostics to make sure nothing obvious has failed.2. pull all electrical connectors and make sure none has corrosion (CAS, PTU, MAF, TPS, AAC, FICD, Air Reg, Injectors, CTS)3. test all of the above components to make sure they are in spec4. what plugs do you have? Stock is best gapped accordingly for mods

i have stock ecu and have done diagnostic test on ecu and showed no codes.

i will be very upset if one of my injectors is bad as i thought my nightmare was over. all my injector connectors are clean of corrosion and i have new oem nissan plugs.

i jus want this thing to run right already.

i guess il bring it in to have the injectors flow tested a.gain as now im terrified one is bad

Just test the injectors with a multimeter. They should read between 10 and 14 ohms to be in spec. They may all be good, I was just pointing out one of a few possibilities. If there is no miss at idle and or when the engine is under load, but it's laggy, then I'd be looking at boost leak, especially if it was better before the recent work.Did you do the o2 sensor test when you did the diagnostics? ECU diagnostics on an OBD1 engine don't always find issues, only points to a possible failed component or wiring issue. The best way is to pull the connectors on the critical components and test them all just to verify they are all working.If you had the plenum off, a boost leak is entirely possible as there are a lot of other associated lines. The plenum gasket is also one that sometimes shifts and doesn't seal properly.Are you 100% sure all the vacuum lines are connected in the right locations? Also, the connector hoses at the turbo output often come loose over time. It's good to check all clamps/hoses on the output side of the turbo ring from the turbo through the ICs and to the TB's. Again, a boost leak test is the way to go. It costs virtually nothing to make the test plug. Just don't pressurize the system to more than about 5 PSI as all gaskets and seals see this positive pressure, and things like main seals, cam seals etc can be damaged if the pressure is too high.

im going to construct a boost tester my next day off of work im hoping its a boost leak at this point.

this vg30dett is frustrating!

It's no different then any EFI engine. If all the mechanical end is good (compression, valves, etc) then there isn't much else to go wrong short of boost leak, fuel supply, spark, one of the sensors or control solenoids of which there are only few (CAS, PTU, MAF, TPS, AAC, o2's, Coolant Temp Sensor) that really count. A couple of hours verifying the essentials usually roots out the problem.

Zwicked wrote:It's no different then any EFI engine. If all the mechanical end is good (compression, valves, etc) then there isn't much else to go wrong short of boost leak, fuel supply, spark, one of the sensors or control solenoids of which there are only few (CAS, PTU, MAF, TPS, AAC, o2's, Coolant Temp Sensor) that really count. A couple of hours verifying the essentials usually roots out the problem.

like i said im just frustrated thats all...my last few cars included a dohc inline four and a boxer style 4 cylinder which were pretty easy to work on so in comparison its more complex.

also i am not a certified machanic and eventhough i can do most installs and diagnostics myself im just gonna have to find someone close by that has expierence with these motors.

my father works for nissan north america so im trying to bring it in to the regional facility this week to have the nissan mechanical engineers take a look ....this was my dream car forever and 50k original miles and im having so many problems it killin me.

il keep ya updated

Yes, it is a bit more complicated than some. If you have access to other tech people, that never hurts. Having a second (or 3rd) set of opinions always is beneficial.I am not a trained tech either, I've just had it for a few years and it does take some time to understand this one.

A 50k Z is definitely worth spending some time on and to keep it. Probably the most enjoyable car all around I have owned to date. Keep us updated and best of luck.

okay well i believe i have found my problem i did some research and time under the hood and found a two prong connector that is not connected on the passanger side of the vehicle from the main wiring harness

i belive it comes from my boost solenoid and i can see on the drivers side that it is connected however i am unable to find the place where this connecter plugs in

i believe the other end of the connecter is stuck between my intercooler piping and intake pipe from when my plenum was pulled,

would this explain why i have been dumping fuel and running so rich and not building boost??

im going to start disassembly on the car tomarrow to snake it out....i hope this fixes everthing

It could explain why it's not building boost. There's one for each turbo (located about center of plenum on the side, under the bottom area) and if it's not plugged in, it would bleed off after hitting whatever it takes to push the wastegates open, like maybe 5 pounds or so similar to being in safety boost. There are a few hoses in that area as well worth checking. Any leak in the vacuum system can have an effect.It shouldn't cause rich condition though unless there is a reasonably large leak and the engine ECU is compensating due to not getting a correct reading

Did you run the o2 sensor test when you did ECU diagnostics?

i also found a leak somewhere near the back of the engine on the passenger side it might be the little vac hose on top of the plenum where its T'ed but can not pinpoint the exact leaking spot

when given a little gas u can no longer hear the leak.....regardless im taking it in tomarrow to have everything looked over

Zwicked thanks alot for all the help bud il let you know how it is when i have it back

well check this out....took the z to nissan north america in new jersey and the engineers were not pleased with the gtr tech who did all the work......i was completely missing my passenger side wastegate solenoid they located my vacuum leak and repaired that so i am just waiting for my wastegate solenoid to come in and i should be set.

WOW, that is shoddy workmanship for sure. I'd mail that guy the bill. Glad you found the issue.