occasionally wants to stall

[ckinart]

hey all,
i had noticed recently that my '94 MTX was starting to have idling trouble. i noticed that when you push in the clutch at above say 2000 rpm when slowing down, the rpm would drop to around 500 rpm before bouncing back to idle, nearly stalling in the process. then after a while, the car would not idle at all on starting, only to idle better after a little driving. well, i just put on a brand new IAC (IAB) valve and reset the idle program, and the idle on start problem is fixed. however, very occasionally, when you push in the clutch with the rpm above around 2000 rpm, the rpm will still drop well below idle before recovering to ~900 - 1000 rpm. am i missing something? can anybody think of anything additional that may be causing this? it's not a serious issue, but it bothers me. sorry for the length, but i like to describe my problems thoroughly. oh, and by the way, i replaced my TPS about 2 months ago, with it set at 0.97 volts on spec.

thanx in advance.

 

[sdpatt]

Try the idle reset again. If the idle speed is not being held up to about 1,300-1,500 rpm while the vehicle is still in motion and the clutch is depressed, the vehicle speed sensor may not be providing the correct signal. One of the uses for the VSS output is to maintain an elevated idle speed while the car is still rolling. Could be a failing VSS. It is located on the speedometer cable stalk above the transaxle casing. You can see it if you follow the cable as it curves down from the firewall to the transaxle.

 

[ckinart]

thanx alot scott!!
i had no idea that the idle speed was supposed to be elevated while still rolling, since mine has never done it . that certainly makes for a suspect VSS thumbs_u now, from the bit of reading i've done, it looks as if the atx and mtx vss setups are quite a bit different, and all i can find is horror stories about how difficult it is to change the vss on an atx. is it equally difficult to change on a mtx? i had a look at mine, and it's in a tight spot, but it doesn't look too bad. is the mtx vss easier to replace? anybody?

thanx again...

 

[ckinart]

hasn't anyone changed a vss on a mtx? any info on the level of difficulty/work involved?

appreciate any input