'97 Taurus GL Wagon 197k: Driving itself, stalling/high idle, tach bouncing


#1

'97 Taurus GL Wagon 197k: Driving itself, stalling/high idle, tach bouncing


Some of this stuff has been going on for some time now (several months … maybe even a year).

1.) Driving Itself:

Car seems to drive itself on my way home from work which is a long, flat road in the 45-55 mph speed range. Once I get into this range, I can take my foot off the gas pedal and the car pretty much maintains speed until I get to an upgrade. I’ve even noticed times when I’m not pressing the pedal but the car is slightly speeding up to the point where I have to keep tapping the brake to keep from getting too close to the car in front of me.

2.) Stalling/High Idle:

Sometimes when I come to a less than smooth stop at a light - say, a yellow light that quickly turns red and I have to stop quicker than I’d want, the car will stall out. This has only happened a couple of times in the last 6 months, but it had never done this at all up to this point, so it’s a new phenomena. Otherwise, the idle is usually at 600 rpm (except recently I’ve been seeing high idles of 2000 rpm every so often, which is really weird!!). Also, it seems like if I park the car on an incline, the engine will turn over many more times trying to “catch” and start - and the whole start-up sequence just feels weak - like it’s not getting enough gas.

3.) Tach Bouncing:

This one’s got me the most concerned because I think it’s the most serious (and potentially the most costly to fix). I completely transfused the tranny fluid a few months ago as a possible solution, by the way, so the fluid (Dexron Mercon IV) is fresh. At about 1500 rpm on the tach, the tach sometimes starts bouncing up and down on the scale and I can feel a metallic engagement/disengagement cycle. If I get above or below this area on the tach, however, no problem. Also, taking off from a standstill -even though I accelerate very slowly and smoothly because I KNOW the tranny is “soft” and will ‘slip and slap’ if I don’t - I’m recently starting to feel a very very brief grinding-like slippage feeling that does not hinder acceleration much at all, but feels very unsettling. This is a new feeling and it only happens every now and then (so far).

You’re gonna say the tranny’s on its way out, right?


#2

Is the check engine light on? If so you can probably find the problem by having the codes pulled from the ECU. The high speed idle (driving itself) could be caused by a bad throttle position sensor or idle air control valve. I also had an ECU go bad on my '88 Escort several years ago, the idle speed would randomly jump to 2-4K rpm when driving down the road, but if I would turn the ignition off then restart the car everything was back to normal.


#3

I think that you have an “air” problem - such as a bad idle air control valve or even just a vacuum leak.

I also think that you have a failing transmission.

As FordMan59 said - have it scanned for error codes. Is the engine light on?