I bought my 1990 300zx na 2+2 5spd about a month ago knowing it had a mis and a tap. had a few people look at it and found which cylinder the miss was coming from. not sure which cylinder# is which but it the drivers side closest to the front bumper. the tap sounds like a lifter but not worried about it yet. so after # days of work getting the plenum off for the first time i did the coolant bypass to save time next time and then replaced my injectors and pcv's because i noticed oil in the valves and plenum. After getting it all back together it didn't want to start. i have to flutter the gas real quick as Im trying to get it to start. it cranks but doesn't fully start unless i flutter the gas. it wont rev over 2000 and is hesitant to do that. it wont idle if i don't stay on the gas it just dies out. Sounds like a huge vacuum leak coming from the back drivers side of the plenum where the iacv(idle air control valve) is. i have no knowledge about this but sounds like the culprit. Looking for advice since Im a younger kid with basic mechanical knowledge but new to the z world.
Recent work:
New Fuel injector
New PCV's(both)
Coolant/Water Bypass
Air Filters
Oil Change
(to the best of my knowledge, again bought it about a month ago)
SYMPTOMS:
Hesitant
Wont hold idle
Hard to start, must flutter the gas
Loud whistle at about 2000rpms (coming from area where the iacv is located)

 

Did you replace the injectors with new ones? Did you install new o-rings on the injectors? Did you replace the injector seals on the plenum? Do you have any fuel leaks? did you make sure the gasket was lined up correctly? Did you replace the o-rings on the balance tube?

Also if you know you have a big vacuum leak, then why don't you fix it? Theirs only a few hoses on the back of the plenum, also google z32 vacuum routing.

 

i replaced with new injector new injector o rings and all. not sure what the injector seal on the plenum is. no fuel leaks. sounds like a huge vacuum leak but it sounds like its coming from the idle air control valve. not a cheap part i've heard of ppl cleaning them out. o rings on the balance tube i did not replace because they still looked perfectly fine.

 

If anyone knows about the idle air control valve please respond bc i know a lot of ppl have viewed this post but have only one reply.

 

There are two hoses that connect to the IACV, it's not hard to figure out if you looked up the vacuum diagram, also did you make sure you didn't pinch the orings when you installed the injectors? And I mean Injetors as in a set of injectors, not one. Seriously we can't fix this for you, you have to actually go and look for these things. A simple search on google for finding vacuum leaks is pretty easy. Also the injector isolator is the big oring that seals the fuel rail to the lower plenum, they get pretty ****ed up over the years and it's not hard to pinch them.

 

im not asking you to fiz it for me im asking for information about the idle air control valve. ive been working on this car and have alldata diy. but the diagrams i have printed out already. i was hoping someone has cleaned up or replaced their idle air control valve and maybe i could get info on there sypmtoms to prove what i believe is wrong hense why i left all the info about how its running. and the fuel rail isnt connected to the plenum. so the injector solator i did not replace.

 

Did you replace A injector or INJECTORS? If you replaced the injectors then you pulled the fuel rail. And yes, the fuel rail is sealed to the lower plenum. **** your Alldata, go on twinturbo.net. And no, when you hear a loud hissing noise it is almost always a vacuum leak. A bad IACV will not cause a vacuum leak or the problems you are having.

YOU NEED TO FIND AND FIX THE VACUUM LEAKS BEFORE YOU DO ANYTHING ELSE!!!!!!

 

Im wasn't a member of this forum until I read your responses and decided to hop on here. You're a douche. This kid is just trying to figure out what the heck is going on with his Z and your getting all ticked off at him. It's sad forum members can't ask questions without the fear of getting scolded for asking.

 

You're the only one ticked off, I'm nowhere near even upset. we can't accurately diagnose something unless we know exactly what he ****ed with. ontop of that we are trying to get some basic information and trying to get him to find and fix problems he even admitted to knowing about, but he doesn't acknowledge it or answer it.

And yes, people should fear about posting something on here, then maybe they will actually try to find the answer before asking a question. You know, kind of like you would do in real life?

 

actually i did research for days on end and couldnt find any good information. Nothing that helped me diagnose it. Thats what i was looking for. Help diagnosing my problem. like i said i have basic mechanical knowledge and thats because everything i know i taught myself all of it by doing it. therefor i assumed people on this forum would be willing to help. Isnt that the point of a forum? A place of information and a place to seek help? Every forum ive been a member of has been more helpful and a lot more welcoming

 

You don't need good information, you need correct information.

Here's the link to the google search I told you to do, you even said for yourself there is a vacuum leak and needed help with the IACV lines.
https://www.google.com/#sclient=psy-...w=1440&bih=781

A forum is a place to discuss the subjects as set forth by the titles of the forum. while the z32 community is welcoming, we welcome people who listen and will take the advice/suggestions given to them.

Also, all of my questions where to get basic info to help you a bit more, but you kept beating around the bush. If you would have listened to my first three replies your car would most likely be fixed by now.

 

Didn't want to read through all the banter... Vacuum leaks on a NON-TURBO will NOT cause this kind of problem, unless you have something like a throttle body hose not hooked up.... (or you just have a massive hole some where).

Have you checked... your fuel filter and PTU, and connections (check for corrosion on injector and coil pack plugs).

if you have a whisle where youre IACV is... there are 5 hoses back there (all run around the driver side of the plenum), fairly large, BUT check the under sides (IE the bottom where you can't see unless you remove them). If you're hearing air, that's terrible on a TT, even worse on a NA, because, frankly, there just aren't that many vacuum hoses on an NA that would affect a problem like this let alone that would make a whistle.

 

first off hoov no i know there is no holes cracks or leaks in the actual hoses because i replaced them all after i replaced the injectors and its coming directly from the iacv so im just gonna replace that. you do not read what i say therefor you have not been helping at all and neither does those diagrams bc i have the diagrams from alldata and second alldata is one of the best automotive sources.
napoleon thank you for your insight. and again ill check em but i know the leak is coming right from the iacv

 

If you would have included (once again) some of this info, then we could have automatically canceled it out as being part of the problem. And those diagrams come from the TT.net boost leak guide which has a nifty section in the writeup on dealing with IACV leaks. And alldata sucks (tried using it a few times, gave up when it says "remove cylinder head" as the first step) for anything but getting a basic rundown on how long something will take, the FSM and tt.net are about all anyone should need for a z32.

 

ok thats understandable but ive been on tt.net and havent seen non turbo information and ive noticed big differences between em. When i did the water bypass the process was the complete opposite and i tried using tt.net and couldnt find a na process

 

There is no difference between n/a and TT IACV's, also what info do you need? If theres a leak then find it and fix it, not exactly rocket science.
O

 

well i have been trying to find a step by step on dissembling and cleaning the iaa unit to see if that would make a difference

 

FSM has the steps on checking IACV and IAA, not much there to actualy clean unless the plenum was filled with sludge.

 

So you joined the forums to call him a douche?

I ask my questions in confidence and after I have gone over everything and made sure that the questions I ask will make sense and I have all the information that these guys need. This is an open forums, not a car dealership, we don't necessarily care if you come back or not.

 

ok took all this information into consideration before i repulled everything again. just got then plenum put back on and connected electrical conections. and came inside to relax. i replaced the iaa and iacv and now hopefully later today itll start and the problem will be solved. i will post back later and let you know.

 

Good luck with that.

 

ok so replaced both units and got the car up and running. it ran rough but figured it was bc it hasnt been started. had to jump the battery to start it. once i got in and tried o drive it i realized it hasnt been fixed. its extremly slow to pick up speed and it barely wants to get up to 4,000 rpms and its a struggle to get there. through all the gearss it barely wants to move like its being strained. got back into the driveway and went to pop the hood and smelled burning. poped the hood and smoke was just pouring out from behind the drivers side headers. theres oil all over the inside of the engine bay down more towards the block. oil level is still the same so i know im not leaking oil. it had been like that when i bought it so im thinking it might of been oil burning off the headers. i noticed a little leak coming from the balancer tub driverside but the smaller oring. im assuming its just the o ring. but the car has no power it might take about 8-10 second to get up to 20mph from a stop and acceleration doesnt get any better after that. i dont think a small vacuum leak would cause this so i need help for things to look at that could cause this problem.

 

Could it not be running on all cylinders? Maybe some of the injectors were faulty/improperly installed.

 

i dont feel like its a misfire but its not hesitant its just slow.. could oild sludge possible cause this the plenum had sludge in it but looking in the oil fill i can see the cam and its shows no sign of sludge in there

 

Ohm injectors, make sure the fuel filter isn't clogged, check plugs, pull codes.

I'm putting money on vacuum leaks, dead injectors or both.