High-speed stall?

What would the possible causes of my car stalling when at highway speeds I disengage the clutch and take it out of gear to coast? I went out with some friends on a little romp up and down 9W New Years Eve (did any body hear us?) and I noticed that if I let the car coast in neutral the idle would get erratic and the car would stall. Regular shifting is not a problem and of course once I put it back in gear it would roar to life. I have no such problems when I'm at a light or at speeds below 30. While the situation is currently 100% avoidable and not major for now I am afraid that it might be indicating some impeding doom. Any thoughts or help would be much appreciated. TIA Jeff Happy New Years everyone!

Loose oil cap.... Maybe. Easy to check. I have seen it affect idle on some models.

I'll check that now. Thanks. Jeff

I have this same problem but have not checked the oil cap. I tried cleaning the MAF and it didnt work. Any other ideas?

I had the same problem on a turbo car - was a diverter valve I think. My bet would be it is something vacuum related. Probably something silly.

That happened to me once after coasting from high speeds to 0 mph but there was no rough idle. The only time I've had a rough idle and stalling is when my MAF needed replacing.

Do you have a cold air intake installed?

And, WHY would someone deliberately coast in neutral from high speeds?

As a matter of fact I do. Are you suggesting that while at speed there is too much air being introduced to the engine? btw, the oil cap is on nice and tight Jeff

In my case, the first time it occurred I just happened to want to coast down a long hill so I pressed in the clutch and took it out of gear. And then after about 5-8 seconds she just stalled.

It happens to me after semi-high speed romps (& high speed) when I go from 6th to neutral & let the clutch out. It has happened twice, but ONLY under these conditions. Others have mentioned the same thing as well. - Cam

why does it matter if you take it out of gear? Sometimes when coming to a toll at 70 mph, I just take it out of gear and slow down rather than downshifting the whole way.

Mine happened only twice at first but it is getting worse over time. I would say that it has happened 10 times now.... HELP US!

Does it happen going from 6th gear ONLY, or other gears as well??

Not sure what the reason is but it's also happened to me before in other cars I've owned...only when going from WOT to neutal. I wouldnt worry about it to be honest. Sounds like cars just dont like that for whatever reason...probably similiar to if someone just ran hard for 2 miles and just stopped instead of slowing down. Body would respond better if you slow down first...

no- there is a reason, a car is not organic.

Coasting on the highway at high speeds???!!! I have driven a manual all my driving life and can't think of a reason to do this. Ever. I would suggest this is incredibly dangerous. Once in Neutral you lose a significant amount of control of the car (because you no longer have power available imeediately if you need it) and if you need to get it back into gear quickly for some reason, you have just lost valuable time in doing so.

These are probably the same guys who put their car in neutral at a stop light and then wonder why they have syncro problems later on.

Actually, it was while coasting up to a stop sign/light, still in 6th, then putting it into neutral as I was braking.....I dont believe anybody was actually "coasting on the highway" as you put it.

Exactly, not one person mentioned they were on the Highway. So it's official, no one knows why this happens.

The pesron who started this thread stated "high-speed stall" and "at highway speeds" and that they were on 9W. YOU aklso stated "while coasting from high speeds".

Actually, I did mention it happened as I was coasting down a long hill and yes there was a red light at the bottom. I didn't realize I was breaking any rules of driving with a clutch. However, the next time it occurred I just happened to be accelerating up through the pattern and I had to pause in between shifts because someone cut me off...and it stalled. So...let's assume you are never supposed to be ever caught out of gear with the car moving more than 30 mph but that it can happen...should the car stall out?

No, the car should never stall in those conditions (or any other conditions). Do you have a LWFW? The stock dual mass flywheel should keep the engine spinning. If you have a scanner, log what the throttle position sensor does when it happens.

I restate that no one stated this happened on the Highway just at High and Highway Speeds. We just want to know why this happens why do folks have to go through so much crap sometimes for an answer to a question? We asked for Help not Hate.

On the egas cars, I would suspect the TPS and on the 99C2, I would suspect the ICV.

neutral at the light.....as opposed to what? Am I missing something here?

Same here. I almost always put the car in Neutral at a stop light. Driving manual transmissions for almost 12 years. Ross

I am guessing as opposed to leaving it in 1st with the clutch in.....I normally put it in neutral if it is going to be a while.

In gear at all times. Why would anyone put the car in neutral, anyway? Putting iit n neutral and releaseing the clutch will only allow the gears to spin unecessarily and require use of the syncro everytime you put it back in gear. You might as well turn off the engine at the same time. The pressure plate is much more durable than are the synco's. No wonder so many complain that they cannot get the car into first at 30 mph. Not to mention that it is not only unsafe to sit at a light in neutral, but it is illegal in many states.

Same here. I was told that leaving it in 1st with the clutch in is hard on the clutch release bearing, as well as being potentially dangerous if you were rear-ended and your foot slipped off the clutch.

The release bearing is designed to last far longer than your clutch will. This is not to say that they do not fail once in awhile. Like your wheel bearings, they are designed to be used. Each and every time you shift from neutral to any gear while the engine is running and the car is not moving, you are using the synco to its maximum. Therefore, your logic of wearing out the release bearing by using it, should apply to the syncro's also? I wonder which is easier and cheaper to replace? Ever been at a stop light or toll booth and seen an 18 wheeler coming up behind you at full speed? How much longer will it take you to get your car moving if you are sitting there in neutral?

That's it, I'm selling the cars. I can't take it anymore. In gear? In neutral? Am I breaking the law? Am I wearing down the cltuch? ARGHHHHH!H!!!!!

I had a quick look at the IL and CA DMV sites and I couldn't find this, though both have rules against coasting down hills.

(my bolding) That's only true if you push the clutch and then immediately change to a gear from a standstill. If you hold the clutch for a second or two, the input shaft will spin down, and the gears will be stationary, and you won't hear or feel a "clunk" when you engage 1st. This is how people started their cars in the days before 1st gear synchros.

So, would you suggest that your teenage daughter sit at a stop light in the city in neutral or in gear, ready to move and what would you do about that semi coming up fast behind you? Remember, you have to wait a few seconds to put it in gear.

The way I do it when at a stop light is put it in neutral and then being aware that my light is about the tun to green I engage the clutch, let it spin down, then put in gear. Sounds like the best of both worlds.

High-speed stalling is a common problem with 350Z owners who have certian short-ram intakes. If you put the car in neutral at high speeds(100+) they will stall. Fortunantly this can be fixed by not putting it in neutral.

I would recommend that she follow LVDell 's method. I would hope that my teen daughter had the sense to recognise that there is a time to wait for a moment before engaging gear so as to protect the synchro, and a time to hurry up to avoid the semi.

I dont want to start a little war here because I respect your opinion and you obviously have a LOT of experience working on our cars. To your point, at a red light and a semi is coming from behind... yeah you have to put it in gear but what is in front of you? Another car? Traffic going across? All sounds pretty dangerous, and how often does it really happen (never happened to me)? ... is the ICV easy to get to? I think that might be the culprit...

It is located on the left side of your 99C2 throttlebody. It is the larger of the 2 devices on the left side. Remove the electrical connection and then the 2 screws that hold the ICV onto the body. Careful with the gasket as you will reuse it. Remove the ICV and saturate with carb cleaner. Carefully move the vertical valve inside it to make sure it is not stuck. Reinstall and you are good to go. Jim

I take it no one here has ever been hijacked or knows of no one who has or has never witnessed someone killed being rearended by another vehicle? Like a person who has lost someone to a drunk driver might preach against drinking and driving, I suspect that if you had, my recommendation for keeping your distance from cars iin front of you while stopped and keeping the car in gear at all times might be more understandable. On the technical side, are you people who have problems getting the shifter into first maybe being to gentle with it. You should force it in as necessary and it will gradually become as easy to shift into as any other gear. As for Porsche Dealers claiming that it is normal not being able to go into 1st gear, ask them why the manual states that you can shift from " 2nd to 1st at 40 mph or 4100 rpm's"

Now your sounding like the ADT commercials around the holidays talking about that too many times they get calls from people that just had thier house broken into, yada, yada, yada...... By the way, I know I for one am ALWAYS aware of my surroundings and constanting think about crap like carjacks, etc, in these cars. Always leave room to "get away" if I see something out of place and always monitor "poeple" on foot aware of any "changes in direction". But when it comes right down to it, if I don't jump the gun and haul @ss on a situation BEFORE it comes to ahead, I am the first one to get the F$CK outta the car and give it right over to ANYBODY with a gun! I have insurnace for my life but not nine lives.

You and me both.

Ok...so is the answer for me to sell my 6 speed and get a tip?

I would never recommend that. EVER...

Jim, Thanks for your help on this, looks like a great afterwork activity for me. Is there a way to manually reset the check engine light? Thanks,

You can dis-connect the battery for a short time....that will reset it. Be sure to have your radio code handy though, as you will need it.

There isn't much crime in the DC area, I don't even lock my doors when driving down Martin Luther King Avenue.

I have a code reader I bought from Autozone, also Autozone will read and reset your check engine light for free.

The Autozone near my house will NOT reset the codes for some reason, only read them for you. They stated they were not supposed to. I purchased a reader from them as well to read & reset my own.

At first they used to let you borrow the reader buy you just leaving your license, then they started doing it themselves but the last guy I used didn't know how to reset. I showed him how since I use to borrow their device and now this? Zesh.. It's good to have your own.

So....I did a little testing and I have nailed down the speed at which the idle goes erratic to be at 53-55 mph. I need to pick up something to read the codes at that point. Will a standard 'autozone' meter read the codes while live or do I need something more sophisticated?

So I did as Jim instructed this weekend. I took off the ICV valve and sprayed it with carb cleaner. Then I took a couple q-tips and reached inside the valve and pushed on the valve and it was indeed stuck. The Carb cleaner and a gentle push with a qtip and it was moving freely. I then unhooked the battery to reset the check engine light. Took her for a spin ~ 30 miles of stop and go, high speed, no stalls and runs like new. Thanks for your help Jim!