Car Shakes a little While stopped - Fuel Injector?

Recently when I am waiting at a red light with the brakes fully pressed down the car seems to shake a little bit. Nothing major but it does not feel right. What could cause this? After reading many posts/threads it seems it might be the fuel injector?

What do you think?

I'd start checking the ignition. It's easier to check that first. Start with spark plugs. Take a look at them.

I have a feeling it might be the Spark Plugs - it is at 84k miles with alot of city driving.

Could it possibly be the Oxygen Sensor?

It only shakes when the brake is depressed while stopped at a traffic signal? No other loss of performance? If you have an automatic transmission, my vote is for engine mount.

Originally Posted by Jkoshy01

I have a feeling it might be the Spark Plugs - it is at 84k miles with alot of city driving.

Could it possibly be the Oxygen Sensor?

I don't see how, although anything is possible.

I like smaglik's suggestion too.
Is it correct that it only shakes while in gear and brake depressed?

There is no loss in perfomance. The entire car shakes a little, nothing out of control. Sort of lke that shake that you get before the car shuts off.
It is automatic transmission.

Thank You

Originally Posted by Jkoshy01

There is no loss in perfomance. The entire car shakes a little, nothing out of control. Sort of lke that shake that you get before the car shuts off.
It is automatic transmission.

With no SES light, and if the rev. counter is staying steady at about 800rpm, it may be wise to consider failing engine mounts as one possibility.

http://www.bimmerfest.com/forums/sho...d.php?t=528870

http://www.bimmerfest.com/forums/sho...d.php?t=634177

Aye! That seems to be it! Read all the symptoms. Recently my coolant leaked (replaced expansion tank) and water pump is just about shot.
Is there anyway to see how bad it is without taking it to a shop? Luckily the shaking only happens maybe just once every few days.

Thanks

So - I got it checked out and the fan is not working. Engine mount looks good. Are these two connected? Fan trying to kick in while stopped leading to the shake? I don't experience the shake any other time and it is once in a while not at all stops.
My expansion tank leaked because I was stuck at a railway cross for 10+ mins and the fan did not kick in and the engine overheated.
I'm glad it's 20 degrees out.

Originally Posted by Jkoshy01

My expansion tank leaked because I was stuck at a railway cross for 10+ mins and the fan did not kick in and the engine overheated.
I'm glad it's 20 degrees out.

You should be able to hear if the fan is working at idle - if it's not, the engine will over-heat and local hot spots in the engine can cause a rough idle (and worse things at speed).

Don't rely on the temp. gauge to let you know when over-heating has started to take place.
It may be that the needle stays in the middle for up to a 40 deg. increase in temp. before it heads toward the red segment.

I don't think the outside air temp. of only 20 degs. mitigates the potential for damage to the engine once over-heating has started.

In hindsight, best to shut off the engine if it looks like a long train crossing.

There are quite a few theories in the E46 forums on why expansion tanks fail.
Over-heated coolant is a plausible one.
The A/T thermostat at the base of the expansion tank breaking up and causing an increase in pressure is a less believable one.
Less than perfect casting of the plastic is a good explanation, whether it's a genuine O.E. tank or aftermarket.
Some feel that the plastic just has to crack after X no. of years - just a question of what X is.
Another theory is that over-filling the expansion tank when topping off is likely to lead to a failure because the cap is unable to handle the pressure as intended.

Hopefully, your new cooling fan and expansion tank will fix everything.

Engine mount perhaps...