I have currently two problems, the more serious which is now rendering the car almost undrivable, happens between idle and 1800rpm. The car whether hot or cold starts to 'kangaroo' until I give it above 1800 rpm (not fun in traffic!) and it smooths out.

The second, that may be unrelated is that when I release the gas pedal the revs occasionally stay at 13-1500 for a few seconds then return to idle. This is most noticeable during 'choke' conditions but exclusively.

Please help I have a essential 2 hour drive tomorrow!

What year?

However, I would blame the Idle Air Control (IAC) valve. It sounds gummed up.

It's an 88 4+3 (i hope my signature comes up now)

Test your throttle position sensor.

Happen to know what the correct voltage should be?

don't depend on your sig. The forum defaulted to "sigs off" for display as a way of saving bandwidth. Did this a couple of years back. There were some who had damned near an entire web page in their sig...

Anywhere from 0.54v - 0.68v at idle and anything near 4.5v or over at WOT is acceptable.

What you really want to test is the smoothness of the sensor which is best done with an analog multimeter. Strap the multimeter on and slowly sweep the TPS to its full throttle position. You want to see the needle on the multimeter move smoothly without jumping up and down or doing other funky things.

If you can get the car to recreate the high idle, that would be a good time to see what the sensor is reading.

Ok, thanks I'll try giving the IAC a clean and check the TPS voltage. What about distributer, coil or HT lead problems? I also wound up my fuel pressure as my gauge wasn't returning to 0. It reads 47 ish assuming its reading correctly.

Had the same "idle hang up" that you describe. Engine wouldn't return quickly to idle speed. Instead it stayed higher for several seconds. I tried several remedies but none worked(iac cleaning, spring on throttle lever of throttle body), etc. Replaced the throttle body(went bigger) and is now o.k. It is known that the throttle shafts can wear in their bores)no bearings) and allow air to enter thus causing the problem. A forum
advertiser, Dave ________, repairs these with bearings. Can't remember his name but others will. Good luck.