My 94' Nissan Presea vibrates when it's not running in "drive" mode(when breaks applied).Why does this happen?

Question

This car is excellent. It's an absolute gem compared to my Mitsubishi but when i switch the gear to D or R from P or N, it starts to vibrate...The engine has been checked and it's totally normal.. When the car is in P or N, the tacho shows the engine speed at 800 rpm which is the normal speed but when i switch the gear to D or R and apply breaks, the engine speed drops down to 500 rpm and the car vibrates... I asked from a few people and they said this is clearly not the gear box but could be because of engine mounts or something.. Anyone knows the reason why this happens? Pls....

I forgot to mention that when i turn on the a/c, the engine speed goes up a bit but i know that a/c idle is not functioning well ( a mechanic showed it to me) However, with or without the a/c, the engine is very smooth when the car is in P pr N modes.. I said earlier that the car vibrates when the gear is switched to D or R and breaks are applied.. Actually, when it is in R mode, the RPM doesn't drop down ( I was wrong) It happens only when the car's in the D (drive) mode... And there's no "check engine" bulb is indicating... Other than this problem, the car's fuel economy isn't the best.. Does about 6 km per litre in town and about 8 outstation which is very low compared to my previous two Preseas..

Answer 1

First lets take a look at your RPM (tacho) which should normally be about 800-900 rpm with the gear engaged. You say it falls off to 500 when the gear is engaged, but otherwise runs fine? The viberation you are hearing is pretty normal for an engine that is barely running. Once an engine falls that far below normal, the engine will struggle to keep running, thus it will shake, rattle, and roll. There should be a decal on the front area or the hood (bonnet) that supplies you with information about the engine, such as what liter the engine is, and some specifications such as engie idle speed, spark plug gap, and ignition timing. What you are looking for is the idle speed, in order to know what the normal idle speed should be with the engine hot. Now, lets look at the causes for the idle speed to be lower that it should be. The first thing you want to look for will be vacuum hoses that are loose, worn, split, off, or craked. Since you didn't state you had any check engine light that came on, I would suspect it is a vacuum leak, and I suspect the vacuum brake booster to be the culprit since you put your foot on the brake when you engage the gears. If you don't find any vacuum leaks, check your air filter, to make sure its clean, and that you can see light through it when you hold it up to the light. Be aware that a clogged fuel filter can also cause this problem. The problem is simple to resolve, but don't go turning the idle speed screw up just yet, as something is causing the ilde speed to be that low. It may be as simple as cleaning the intake with an intake cleaner, or replacing the PCV valve. Buy some STP fuel injector cleaner in the black bottle (not the white) and put that in the tank with about 3/4 tank of fuel, and see if it straightens up. It may even be a lazy or sticking injector, and this cleaner will resolve the issue. If none of this fixes the problem; have the Idle Control Valve (IAC) cleaned or replaced, as this is what tells the computer what speed to maintain the engine. I would think there should be a check engine light if this is the problem though. You can always find the screw that controls the engine base idle, and bring that up until its about 800 rpm with the gear engaged. I hope I have been able to point you in the right direction. Good Luck!!!
Do This:
If the car only does it in D, and your fuel mileage is down; This may indicate there is a problem with the transmission lock-up converter not dis-engaging as it should be. You may have to have the transmission serviced and/or add a bottle of Lube-Gard to the fluid to correct the sticking valve in the transmission. You can get the Lube-Gard at most parts stores. Get the one in the white bottle ONLY. This should fix the problem, if it don't then you will have to have a transmission shop take a look at it.
check:
I would like to add; have the motor mounts on the engine checked this way. Put the transmission in D, and hold the brake on firmly, while someone else watches the motor from the side of the car so you don't run over them. Stand on the accelerator pretty hard to say about 3,000-4,000 RPM, and if you have a broken mount the engine will stand right up off the mount. Be careful to get off the accelerator pedal pretty quick if the motor tries to come way up. You can try this in R also to check the other side of the mounts.

Answer 2

Wow, these are pretty hard questions! (my answers aren't too great but that's all I could come up with) 1) I guess that fight got a little too carried away. 2) I got kind of crazy the other night when the Wings won the cup and pleaded Holstrom to convince Lidstrom that he should have a sleep over at his house and for some crazy reason invite me 3) Well, I guess I was drunk (that's why I don't remember what happened! lol) and I accidently spilled my soda on top of Hollweg the night of the game and he got revenge (along with Orr and Dawes)! 4) I was camping with some friends and then before I knew it these hockey players come along (when my two friends were both sleeping) and it's dark out and I heard some noise. I was knocked out not too long after. When I woke up I heard one of them say something about how hungry they were and how disappointed there wasn't much meat on me. It turns out that I was tied up and was supposed to be dessert. They must have been drunk to think I was similar to the rabbit they were roasting - I suppose they thought I was some kind of puckbunny - literally! lol

Answer 3

Your car is old enough to need the motor mountings. "Insulators" Nissan calls them. However the basic idle speed in gear seems a little low. Does the idle speed rise with A/C on and when you turn the steering all the way past the end steering switch idle up. That way we know the IAC AAC valve is working. Idle Air Control Air conditioning air control. The valve is loacted on the intake. This valve can be adjusted but you have to have specialized tools like Consult 2 your dealer may have to be contacted.

Answer 4

Hi,
Well, the drop in rpm is normal when you put it in gear.

I would check two things
1. motor mounts-this can be done by using a jack and lifting up on the engine(gently) see if the mount separates.
2. there is a transmission mount at the rear of the trans if this is worn out it will cause this vibration also.

Answer 5

Almost all 4 bangers (it IS a 4cyl isn't it?) vibrate under these conditions. It's the nature of the beast. If it's a V6, have the idle speed adjusted, and maybe a tuneup.