Shuddering?

[FastbackBoi]

Hello folks, i have a little question about my 91 240's engine...

lately ive noticed while idling at stoplights, that every few seconds or so, i can feel a slight shudder in my car. when i first noticed it i kept paying attention and it does it often. i decided to see if it was just at that rpm, so i raised the rpm to  1000, 1500, and 2000  for about 1 min each and payed close attention, and apperantly the slight shudder shows itself regardless of the rpm.

what i want to know, is if this is a bad sign (which im pretty sure it might be), and if so, what is causing it and how could i fix it?

also i notice if i like, have the clutch down and the engine is at idle speed, and then i quickly push the gas down a decent amount and let the rpms jump to about 3000 or so then quickly release, the engine shudders (sways) back and forth somewhat violently, making it easily felt inside the car.

as ive made clear in previous posts, im not quite experienced with cars, but i get the feeling that these are bad signs <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/tounge.gif" border="0" valign="absmiddle" alt=':p'>
sorry if they are n00bish questions, but then again i am a n00b lol.

any enlightenment on these observations of mine is appreciated, thanks in advance <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=':D'>

[guidot]

Your engine mounts could be gone, as well as you may need a tune up. &nbsp;Cap, Rotor, Plugs and Wires are a good start!

[FastbackBoi]

how would i go about checking the engine mounts? (i.e. what is the location of them and what should i check for when inspecting them)

and if they are gone, i take it the shaking of the engine could be damaging it, am i correct?

and what is most likely the cause of the slight, quick, periodic shudder of the engine at idle and other speeds?

sorry for the spew of questions, im just concerned about my baby <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/tounge.gif" border="0" valign="absmiddle" alt=':p'>

i dont want to kill it far before its time, or cause any costly repairs to be needed <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/sad.gif" border="0" valign="absmiddle" alt=':('>

again, i appreciate your help <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=':D'> thank you.

[geeaj]

Highly unlikely it is your engine mounts, otherwise, you'd be shuddering during acceleration and decleration as well when the motor is "twisting" the mounts.

Your best bet is to do a complete tuneup and pay special attention to your plug wires, cap, and rotor. Should also check your MAF and the rubber boot leading to the intake. I suspect you may have a crack in it and have some airflow issues. If there is a crack in it, your engine will seem like it is gasping at low rpm and stoplight idle situations.

[Arcane]

aint this in the FAQ?

and i applaud you for being so polite and professional...imo, this isn't a n00b question and is warranted...but a quick glimpse in the FAQ would have been appropriate too...eh...either way...glad to have you in the forums...happy postings...

yes, i know...i'm being nice...weird isn't it?

[bheld]

could also be fuel problems...fuel pump maybe?

[S13Grl]

You should not check your fuel pump right away. If you have the proper tools, you may want to check for pressure (fuel) output. I would not be worried about it, it's normal to have some shuddering. It happens to me with my car when I tap the gas gently and I also have a '91.
If I were you, I would just replace the air filter, check the IACV, and maybe pour some fuel system cleaner down the tank and use good quality fuel.