Bdan57

Hey everyone, new to the forum and needed some advice on what to do about a stalling problem.

I got a 96 300zx na manual trans. with 141,000 miles just before christmas. It has near flawless interior and good exterior. The car is completely stock. Oil was just changed with synthetic, air filters replaced with K&N air filters, and new spark plugs just put in (NGK Platinum). The head cover gaskets are leaking a little oil, and the a/c compressor needs a fix. Those are the only known problems besides this stalling situation.

So, back to the problem, what's happening is when you are coming up on a stoplight or a turn, if you are going more than 30mph, and you engage the clutch to just "coast" up ahead, the car will completely shut off. What I have to do to downshift is brake until the rpm's drop to around 1500 rpms and then change gears. When upshifting, there is no problem. If I'm at or above 3rd gear and im coming up on a turn, most of the time I just brake and let it drop down to about 12-1500 rpms and make my turn, instead of downshifting all the way to 2nd.

Right now, the problem seems to be under control. I drive it daily and I have learned to drive so that the car doesn't stall, but I am worried that letting this problem continue could make it get worse. I also took it to my uncle(mechanic), and he thought it could be the idle, so he adjusted that, but it wasn't the problem. He also threw the idea out that it could be the egr valve, so I don't know.

Any ideas that you guys can give me would be greatly appreciated. If you need more details, just ask and I can post more details about the problem.

Thanks,
Brandon

ZLover4Life

What kind of K&N air filter are you using? Is it a cone filter or a drop-in OEM replacement?

Most common causes of stalling when coming down from speed are turbulence at the MAF (caused by an improperly installed cone filter), or a plethora of vacuum leaks.

KasbeKZ

tell your mechanic to stop adjusting the idle because he probably doesn't do it right, and it shouldn't need to be adjusted unless someone has already messed with it or something else with the engine set up has changed. other than that, it's just a way of masking certain problems.

Bdan57

The K&N air filter was just an OEM drop in replacement. The problem existed before the air filters were replaced also. If it were vacuum leaks, what would I need to do or tell a mechanic to do to fix the problem? With regards to the idle adjustment, I think he adjusted it because it was idling high (around 1300 rpm) and its now just under 1k.

Thanks guys, any input is helpful, I'm pretty clueless when it comes to cars, but I'm trying to learn more and more.

KasbeKZ

when the car is idling too high, it's because something is wrong, not because a tight screw just got turned over time. stuff has to be fixed rather than masked by adjusting the idle. there are a ton of threads on the forums about finding high idle problems, and they all start with the "pinch test". there's a good search topic. once it's confirmed that everything is working as it should, then it's acceptable to assume someone else has adjusted it up at some point, and it can be adjusted down, through a specific process dealing with disconnecting the plug closest to the adjustment screw.

Bdan57

So do you think the high idle and the stalling are related? Do you think if I found the source of the high idle it would fix the stalling problem? Wasn't able to find much on the pinch test, what does that involve?(if you have maybe a link to info on it that would be great). Z's are all new to me so bear with me. Also, do you think driving around with this problem is okay for the time being? It's been going on since I got it, but like I said I've kinda learned to avoid the problem so it doesn't stall out on the road. The idle hasn't changed since it was adjusted, so I guess my main concern is to not damage something mechanically.

ZLover4Life

They are both likely caused by an air delivery problem.

Driving around with the problem is probably fine - you're likely just wasting a little fuel.

You need to get a boost leak tester... you can find them in classifieds on TwinTurbo.NET or you can make one - it's just a PVC plug that fits into the intake T (you'll have to remove the intake box and MAF), and you thread an air nozzle into it. You then pressurize the intake tract to about 5psi (NO MORE THAN 5psi!!!) and listen for air leaks. Find the leaks and replace the hoses that are causing them.

If you don't have a compressor, you can just get a bunch of new rubber (not silicone) vacuum hoses and start replacing them (one by one, lest you mix some up and really cause damage). In nearly two decades, I'd suspect probably all of your vacuum lines are dry-rotted, so it would be a good idea to replace them, anyway.

Finally, zip-tie the ends of all vacuum lines to ensure a tight fitting.


Also, how far north in North Carolina are you? There's a damn good Z32 tech in northern Virginia if you wanted to take a weekend trip to have it fixed. Do not take this car to your uncle or any other mechanic again - it is too advanced for any mechanic not well-versed in the Z32.

KasbeKZ

i believe there's somebody good in virginia beach as well? that's very close to northern NC.

Bdan57

Okay guys, I appreciate it, I will look into getting the vacuum hoses replaced. Do you guys know of any good z shops in North Carolina. I'm in central NC, so Virginia is quite a drive. If not, I could probably find time to get up there, just wondering if you guys knew of any in NC. There is one that opened in knightdale called the knightdale z shop, but I don't know how reputable they are.

ZLover4Life

There are only two people/companies I'd let touch a Z32 of mine... one is in California, the other is in northern Virginia.

KasbeKZ

haven't heard of them, wouldn't trust them. it probably really is worth the trip up to bernie.

Bdan57

Okay guys thanks once I get enough money to make the repair I'll probably make a trip up there to get the problem fixed.

KasbeKZ

or in the mean time you could let us help you out getting it fixed yourself. i hate to take business from bernie, but if you can't afford it, you can't afford it.

Bdan57

That would be awesome man, I would have to have step by step instructions though. I'm not knowledgeable about working on these cars whatsoever, but I trust that you guys know what you're talking about. If you get the time, just tell me what to do to get started as far as dealing with these vacuum hoses. I know Zlover said I needed a boost leak tester, should I get one of those to start with? Would I be able to obtain one from a local auto parts store, or does it need to be ordered off the internet. I would make one myself, and if I knew how to read Zlover's instructions I would, but like I said this is really all new to me. Help me out with this if you have the time, I'm not trying to take up anybody's day with my problems. Thanks!

KasbeKZ

he's going to be a much bigger help than i am if he chooses to be, but i'll throw in what i can.

http://boostpro.net/prodtester.html

looks like a product there will help you out. you need one for a single pop with a gauge and a tire valve adapter. looks like $25. i doubt you can make one for much less than that.

in the mean time, get some electrical connection cleaner from any automotive store. WD-40 is also capable of the job, but is inferior. there are three connections that i'm going to recommend cleaning. i'm going to use the courtesyparts diagram to show you

http://www.courtesyparts.com/300zx-p...3_884_898.html

there are two connectors on 23781m and one on 22660m that should be disconnected, sprayed, brushed (with a tooth brush or soft wire brush or something), and scraped with a small screw driver or ice pick like tool. scrape the inside, and scrape the male posts on the units. so you'll be cleaning the male and female ends of these connectors. remember, we're just cleaning these off. don't break them. make sure the females are gripping their posts securely. you can bend the sides of the metal female connectors inside the larger plastic connectors slightly to make them grab harder. put this stuff back on and make sure they click and are on securely.

these connectors are on the rear of the plenum, and down a bit. they are not impossible to reach. you just have to gently move the wiring harness out of the way sometimes. they are on the drivers side.

this is not the most likely problem, but i have had the problem that you describe fixed by cleaning all of these connections.