need a VG30DE expert

[SnakeKack]

A friend of mine just bought a 1990 N/A 300zx. Everything on it is cool but he explained a problem that it seems to have very often. He said said at low speeds it sometimes acts like it isn't hitting on all cylinders. I told him I would drive it and see what I can think of.

At first I didn't notice anything at all. But then after a few minutes it seemed to start acting up. At slow acceleration and rpms it moves funny and doesn't move very fast, also when you come to a stop and go to press on the gas pedal it won't press in is like it get stuck so you have to push hard which ussually causes it to take off kinda. Now here is the interesting part, when it gets to about 2500 + rpms its fine. And when you floor it or get on it a bit its fine, no problems at all. At idle it is fine and when you rev it it seems fine too.

I told him to check his connectors, replace the fuel filter,sparks plugs, and clean the injectors. I really don't know much about these engines. But I did notice something interesting, when standing in front of the car on top there are two throttle cables next two each other. The one on the right looks fine and is tight, but the one on the left looks like it has a slight bend to it and its not very tight when I tug on it. It seems pretty loose actually. I wonder if that has anything to do with it.

Any help would be much appreciated, thanks.

[rrobe99999]

Sounds like you found the problem. At idle, both throttle plates are closed, so its fine. When you floor it they are both open. But since one cable is loose, the midrange positions are different, which causes one side of the engine to get less air than the other. Tighten up the loose throttle cable.

[ranisron]

Clean the MAF (wait, does Z32 run on MAF or MAP) sensor.

[SnakeKack]

Ok, so before we tighten it, I heard that one of the cables is for cruise control, I am not sure if it is true or not. When he revs it and I watch, only the right cable moves, and seems to make both throttle bodies open. But there isn't anything stuttery about it during reving it.

Also he told me something else that happened today, when he started it up when it was cold it idled kinda crappy and the idle was real low (fast idle sensor?). He went to put it in reverse and it stalled. So he started it up again and rev'd it to warm it up. He said white smoke was coming out at higher revs, not idling or low revs.(doesn't sound good to me).

Thanks, all help is greatly appreciated.

[bardabe]

the Z32 uses a unique throttle body cable style, there is not two cables for the 2 throttle bodies silly kids. one cable is coming from the pedal and another is coming from the cruice control solenoid. one or the other cables being loose should not affect your idle. why? simply because you have what is called a Throttle position sensor so that tells the ECU how far the thorrle bodies are open. (I know you will ask how it;s possible to open 2 throttle bodies with only one cable. the 6 bolts holding the cover will reveal the shocking answer to you I'll let you find out on your own for the suspence.) so clean your TPS conector and TPS sensor plug with some "electric parts cleaner" the maf should not affect your Idle. uf the MAF is bad you won;t be able to rev the car past 2500 RPM's. you might want to check your Air filters however a cloged filter can affect performance drastically. I also recomend you clean your throttle bodies and AIV system (follow this write up http://300zxclub.com/showthread.php?t=59296 you can thank CC for it) after that is done and your Idle is still crappy. check for vacum leaks. and make sure all the vacum lines are properly conected and where they are suppose to be conected.(look here for further details http://www.300zx.co.uk/cgi-bin/manual.cgi?list=efec&dir=&config=&refresh=&slide=1&cycle=off&scale=0&design=default&total=190) once all that checks out. clean all the coil pack conectors and Injector plugs. make sure all your grounding points are clean and tight. replace your Fuel filter and make sure your plugs are properly gapped and in good working condition. and this should take care of your Idle and Hesitation problems.

The white smoke well that is Kind of scary, since this is not a turbo car you can;t be burnin Oil or coolant through the turbo. so what other cause can this be??? you guessed it Leaking Head Gasket. nwo there are 3 ways to check for this. one is Coolant mized with oiil. to see this simply open your radiator afte rthe car sits overnight and it;s nice and settled. if you don't see any cofee like stuff in the coolant proseed to the next step. Run the car untill it warms up. and then park on the side of the road and while the car is idling remove the Oil cap. and look under it if you still don;t see any cofee like stuff or mily stuff you are close to being on the clear. final step for leaking HG now that your car is at runing temperatures unplug your fuel pump relay or fuel pump and let the car run untill it dies. now give it a few more cranks to make sure all the fuel is out of the system. take out allthe spark plugs. and do a compression test. (http://www.300zx.co.uk/cgi-bin/manual.cgi [engine mechanical page 9] yep) if this checks out fine you don't have to worry about a leaking head gasket. because your problem is slightly easier to fix. so if all of the above checked out fine adn you are still spitting out white smoke out the back. you have a leakig injector or bad injector O-ring. so you change the injector O rings or all your injectors adn take it for a spin and now you should have a Nice and Solid VG30DE. enjoy! you can ask me anithing Via AIM or IM me for my number Don't be scared I don't bite

AIM: wanton TD

-Juantons

[SnakeKack]

:eek: Geez lol thanks I got way more info than I expected. I heard from other people that those cars get throttle body an fuel system problems alot. I will definilately tell him to try these things.

I forgot to mention one thing about the car, and that is I noticed the oil pressure guage doesn't show much activity. Its always on a low position and reving or getting on it doesn't make it move much, but it does move a little, real slow though.

[bardabe]

:eek: Geez lol thanks I got way more info than I expected. I heard from other people that those cars get throttle body an fuel system problems alot. I will definilately tell him to try these things.

I forgot to mention one thing about the car, and that is I noticed the oil pressure guage doesn't show much activity. Its always on a low position and reving or getting on it doesn't make it move much, but it does move a little, real slow though.
these are real highmaintenance cars. I use to own one. it was rather complex system. I studied the car alot. became a Z Junkie for the longest. untill my dad desided to build boost in the rain adn ended it;s legacy. but mine never gave me problems always gave it a good clean kept it up to specs.

about the Oil pressure gauge clean the Oil Pressure sending unit. (next to oil filetr) and check conection if you need a new gauge I have one laying arround. but it reads in BAR though. but it;s a direct swap in

[ranisron]

Z32 is a beautiful car. But looking at the engine bay (and see how cramp it is), it turns me away.

EDIT: I forgot to say... if you have a blown/leaking head gasket, doesn't your engine temp shoots up? I know the factory temp gauge is not the best, but it will sure tell if your water temp is going off the roof.

[bardabe]

Z32 is a beautiful car. But looking at the engine bay (and see how cramp it is), it turns me away.

EDIT: I forgot to say... if you have a blown/leaking head gasket, doesn't your engine temp shoots up? I know the factory temp gauge is not the best, but it will sure tell if your water temp is going off the roof.
the Z32 gasket is pretty hard to bllow. but if you actualyl manage to as you can see his has not gotten that bad since he only shoots white smoke at higher RPM.s wich means it's a minimal leak in fluids in the combustion chamber. this should show in the compression tests. and no the Factory gauge on the Z32 is actually pretty good.

[SnakeKack]

Whew, we went to CarQuest and looked for Throttle Body cleaner, and one of the employees told us about SeaFoam. This stuff it pretty neat I don't know how I didn't know about it before. We poured some into the vaccum line and it smoked only a little bit, but the hesitation thing is virtually gone now, he is real happy. I will probably have him put the rest in the gas tank.

[bardabe]

Whew, we went to CarQuest and looked for Throttle Body cleaner, and one of the employees told us about SeaFoam. This stuff it pretty neat I don't know how I didn't know about it before. We poured some into the vaccum line and it smoked only a little bit, but the hesitation thing is virtually gone now, he is real happy. I will probably have him put the rest in the gas tank.
yeah that thing works nice but it kills your sparkl plugs. good to hear your hesitation problems are gone. after the seafoam is all consumed tell him to change his spark plugs. and use Factor y OEM NGK's ONLY! other wise he will regrett it in th elong run look at this for proof

http://www.zdriver.com/forums/showthread.php?t=15019

-Juantons

[Neejay]

Also, be sure to do a leakdown and/or compression test.

[SnakeKack]

So should I tell him to get the NGK PFR6G-11B plugs for his NA? or is there another one?

BTW the help is greatly appreciated.

Lol I am liking these cars more and more, the interior alone, and the t-tops are what really attracts me, I kinda want to buy one. Wish I had the money and time.

[bardabe]

no what I am trying to sya is get the OEM N/A NGK spark plugs for Z32. (U can get them at Kreagen) if you put the Extended plugs on the N/a it will come in contact with the pistons. (N/A Pistons are taller than Turbo pistons but the head is exacly the same.)

[SnakeKack]

Hmm, I was looking up the saprk plugs on autopartswarehouse and prostreet, and I noticed something interesting.

It says there are 2 recomended spark plugs:

use 6 of NGK PFR5B-11
(hot heat range for
low speed driving)

use 6 of NGK PFR6B-11
(normal heat range;
platinum)

For the PFR5B-11 it says for low speed driving.. does that mean its not good to go fast?

And for the PFR6B-11 , you said it wouldn't work for the NA because those are for the turbo.

Just for fun I looked up spark plugs for the turbo and this came up:

use 6 of NGK PFR6B-11B
(cold heat range for
high speed driving)

use 6 of NGK PFR5B-11B
(normal heat range)


Lol, sorry, if anyone can explain this to me I would be greatly appreciated.