I have an 88 Turbo II, not sure if this is normal, as my TII is the only one I've ever been around, but the idle is kind of strange.

Once its up to operating temps, it will idle at a perfectly normal 750 rpm but every four or five seconds, the rpm drops to about 400-500 rpm and the car shudders, but then go right back up to 750 and is smooth for the next four or five seconds. It does this constantly. On one occasion, it stalled out in the driveway. Other than idle though, it seems to run fine.

 

Check the sparkplugs/cables, O2 sensor and TPS.

 

What is the procedure for checking the O2 sensor and TPS? Sorry, I'm a noob, is there any special equipment invovled?

 

Also, check for any vacuum leaks.

 

Also, check for any vacuum leaks.

 

there is a whole bunch of threads on this topic, doing a search will yield a lot of val. info.

I have an 88 vert and I have a very eratic idle on it also.
sometimes it will die at the stop lights (very embarassing) I raised teh idle (bad thing to do) to resolve it.

another vert owner graciously assisted me in checking my ecu codes using the led light ecu checker (u can make this yourself) and we found that my o2 was out.

1. installed a new O2 sensor.

things I have read that I need to do

2. put in a new fuel filter (user have reported that this resolves their idle issues)
3. adjust my TPS
4. check for vacuum leaks - I found that found of hoses that were loose and the exhaust back pressure hose had the wire clamp come off it just above the ext manifold.
5. Grounding - I scrapped all the grounds clean and tightened them.