Speedo not working and car stalling?
 

Hey guys, I have a very interesting problem with my 97 GT 5spd! The only mods it has are exhaust (flows and bassani x-pipe that have been in for about a year, and a steeda shifter, also in about a year).

The other night, I started up the car and noticed that the speedometer wasn't working. It just sat at zero without moving, twitching, anything at all, at all speeds that I drove at. Also, there are no miles registering on the odometer or tripometer.

This isn't the worst part though. A few minutes later, I was braking from (about) 60-65mph and the car stalled out when I had the clutch in and was braking! This sucks because I lose power brakes, power steering, etc. I had to start the car back up quick and continue braking. It didn't stall twice in a row or anything, it seemed normal, so I thought it was a fluke thing. Apparently it isn't a fluke thing though, it does it regularly when I brake from what seems like above 50mph. It hasn't done it yet when I am not going above what seems like above 50mph. Basically, if I haven't made it to 5th gear, it won't stall, but if I have made it to 5th, it will stall when I have the clutch in and I'm braking. It is a very smooth stall, no sputtering or anything at all, it just basically comes off the current rpm (say 2.5k) and goes straight down to zero very smoothly.

I can't think of any possible reasons? I am wondering if the speedo problem and the stalling are somehow related? I'm not really sure where to start.

On a side note, in case it is applicable, about a week ago, I ran over an island curb in a parking lot pretty hard on the left side only :( It shook it up pretty good, but it seems like it has been alright since (for about a week, driving it everyday), I haven't noticed any problems. I looked underneath from the side and couldn't notice anything obvious, doesn't look bad at all, but I haven't had it on a lift to check.

Any thoughts on what the problem(s) could be, or where to start? Thanks for any help!

Re: Speedo not working and car stalling?
 

I was reading quick on another forum about a different car (not sure make or model) that was experiencing what seems like the exact same stalling problem (no mention of speedometer). The person said that it was the IACV (Idle Air Controller Valve) that was the culprit. Does my mustang have one of these and if so how could I go about checking it?

I was also thinking, is it possible that this is a vacuum issue of some sort? I'm going to check quick when I get home, I just haven't had the time since I got home after the problem.

Re: Speedo not working and car stalling?
 

An update on the problem:

It seems to do it at all speeds, as long as I was moving, shift either into neutral or put clutch in, and I brake. The rpms come down from whatever they were, pass right by the idle rpm, and go down to zero. This is in a sometimes slow, smooth motion. Sometimes the rpms will sit at 400-600 rpm for a split second and it will either come up to idle or stall out. If I tap the gas it will come up, and seems that it will not stall after this, as by this time I am usually at a stop.

Seems that it just cannot "catch" the idle when moving and braking and not in gear. What component controls this, and is it related to the speedometer not working?

As far as the speedometer goes, I crawled under the car and searched around for the cable the best I could, the only thing I found that resembled a cabled going into the transmission was a thick black rubberized cable coming off the driver's side front of the transmission and heading straight toward the engine. This looked more like a hose, but was quite stiff, maybe 3/8" or 1/2" in diameter. It appeared to be securely connected, though I couldn't really tell how it would be disconnected even if I wanted to.

Any thoughts before I give in and take it to a dealer?