This is not a good thing....

[Frappe]

Sometimes, most often in 2nd gear, when I shift into the gear the car will spasm violently back and forth. Not like a "give me more gas before you let out the clutch" feeling, but it's like I'm mashing the gas and then releasing it over and over again very quickly. It's physically painful, and absolutely terrifying.

The previous owner of the car had installed a throttle body recently, so I will be checking that. It sounds like maybe a loose/bad Throttle Position Sensor, or Vacuum Seal problem...but I'm not really sure.

It will do it in the higher RPM range of 1st as well (4k+ usually) but not nearly as violently. In 2nd gear, it's mostly independent of what RPM I'm at, but tends to go away if I growly at the car, push on the gas pedal, and tap at the clutch a bit...but I think that's just luck. It tends to go away in 2nd gear also if I bring the RPMs to about 5k or so with the driveline engaged.

I'm going to take a look at the throttle body and all the vacuum lines I can see today, because this is making the car nearly undriveable and very uncomfortable.

If anyone else has ideas for things I might want to check, I'd really apprectiate it. Sorry about the long post.

oh yeah, if it makes any difference it's a 96 S14 with not quite 100k miles on the engine, and an awful awful second gear synchro.

-Frappe

Edit- would it be a worthwhile thing to change the transmission fluid while I'm at it? help with the shifting maybe?

[Foxcolt]

This probably isn't the problem but better safe than sorry.

I had almost the same problem however is was on an SR. Turns out the maf sensor wiring was bad. Whenever the mafs would get disconected the car would buck wildly. Checks your mafs. See if the plug isn't in all the way.

Hope this helps
Jed

[Frappe]

I went out and checked the throttle body this morning. and the MAFS. The sensor itself looked downright clean, and the plug is in all the way (took it out and replugged just to be completely sure). I also re-connected the Air Intake Temp. Sensor.
I haven't taken the car out yet to check, but I'll post when I have...I think that if it's still a problem by this afternoon I'll take it down to the shop...

-Frappe

[Starlin]

My '89 does this to occasionaly if I try to idle along in first gear. I never worried about it and I hope it doesn't grow into the same problem you're having. Please let me know if you get it figured out.
Starlin

[Sil80girlie]

I dunno if this is the problem or not, but I had (what sounds like) the same thing happen to me a while ago.  I believe the prob was just that I needed new spark plugs/wires.

[Frappe]

OK! I took her out this morning, and it's all fixed. I checked the MAFS, the vacuum lines, the hose clamps, the TB, etc.

And I removed one loose power wire that was powering an amp that I removed before hand (whoo, free money &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/wink.gif" border="0" valign="absmiddle" alt=''> )
(see post in Sell/Buy/GB section for prices on the amp and sub &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/thumbs-up.gif" border="0" valign="absmiddle" alt=':thumbsup:'> )

I'm almost positive that the problem was that wire. It would hit the + battery terminal during driving, and would interrupt the current until it was shaken off again. Hence the violent shaking. Thanks for the help everyone, I did in fact find a loose hose clamp which I tightened as well.

-Frappe