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1997 Ford Taurus 3.0L Wagon 226,362 miles
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Discussion Starter · #1 ·
'97 Taurus GL Wagon 197k: Driving itself, stalling/high idle, tach bouncing
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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?
 

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I also have those problems: the car seems to accelerate by itself at the 55-60 range without even touching the gas and eventually after about a minute it starts to slow down. I also see that I have high rpms when I shift into nuetral without touching the gas goes up to about 3200 rpms and back down to 2800 and eventually when car does start to slow down, the rpms will go back down. Seems weird, I though when you disengaged the transmission the rpms go down to idling spend.
 

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Driving Itself:
Once you release the gas pedal, throttle plate closes. Once the throttle plate closes, air flow goes down. These changes are governed by mechanical linkage and law of physics. No electronic control can overcome release of gas pedal.

You may want to check if the throttle plate linkage is moving. I heard before the cable is corroded and stuck inside the cable housing. Idling control motor may be stuck open, bypassing closed throttle plate.
 

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1997 Ford Taurus 3.0L Wagon 226,362 miles
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Discussion Starter · #5 · (Edited)
sfontain:

I strongly believe you are right. I've had "lean" codes on this car for a few years now that imply vacuum leaks. How many vacuum hoses does this engine (3.0L Vulcan) have and where are they? And what's the technique for finding the leaking ones ... or should I just replace them all since they're all originals from the factory (and it wouldn't cost that much)?

I know there are the larger vacuum hoses coming off the unit on the firewall, but aren't there also several small 'elbow' hoses here and there around the engine that could be leaking, too? And what do you do - buy a roll of hose and cut it to length for all these small pieces, or do they sell them individually?

paker:

I'll look into your suggestions after checking for the vacuum leaks sfontain mentioned
 

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Discussion Starter · #7 ·
Yeah, the diagram is still there, but it's not clear (to me, at least). I'll just have to sit down and look at the manuals for a while ... like I usually do.
 

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The intermittent super high idle and the cruising without the pedal being touched sounds more like an idle control motor to me. The lean codes point to vacuum leaks as other have mentioned. The transmission may or may not be having genuine problems, I would pull and clean the intakes and replace all vacuum hoses, intake gaskets, clean/replace the IAC and see if the transmission issues disappear. Driveability problems can confuse the transmission and create symptoms that feel like what you describe.

You didn't use the best fluid, BTW. Really should have used Mercon V.
 

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The intermittent super high idle and the cruising without the pedal being touched sounds more like an idle control motor to me. The lean codes point to vacuum leaks as other have mentioned. The transmission may or may not be having genuine problems, I would pull and clean the intakes and replace all vacuum hoses, intake gaskets, clean/replace the IAC and see if the transmission issues disappear. Driveability problems can confuse the transmission and create symptoms that feel like what you describe.

You didn't use the best fluid, BTW. Really should have used Mercon V.
Colt: Open your hood, start the car and let it idle. Unplug the electrical connector from your idle air controller. Engine should stumble or even quit running; if it does, your IAC is NOT stuck open and this is further evidence of a vacuum leak. Every symptom you describe is explained by a vacuum leak, and some of it is NOT explained by a faulty IAC.
 

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Colt, the way to find vacuum leaks is by filling a spray bottle with soapy water, spray on warmed up engine vacuum lines. If you see bubbles you have found your leak.
 

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Tps

'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?
One more trick.
I had older one, '93 Lin 3.8 that would decide to run at high idle and stay there every once and a while. As a test, I pulled the connector off the TPS while idling. It did exactly what randomly happened. Full high speed idle, if you can call that idle. Maybe 3K rpm. Replaced the TPS and that fixed. You could pull the connector of the TPS while idling and see if it makes it act like your issue. Loss of TPS causes the engine control to not know what is going on. It can't control idle speed beacuse it does not know the throttle is at idle. Default is full speed ahead.

-chart-
 

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Faulty IAC Valve

I think I might have that probelm. Mine does the same thing and if I shift into nuetral and let of gas, the rpms go up to 3200 from about 2100 and then back to 2800. It will continue to do this until the you put back into gear. I have pulled the connector out of the IAC valve and the engine stumbles, try to drive it and it quits. Could the IAC be interminently failing?
 

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Colt, the way to find vacuum leaks is by filling a spray bottle with soapy water, spray on warmed up engine vacuum lines. If you see bubbles you have found your leak.

Ya, that's not going to work for a Vacuum leak. Bubbles don't appear under vacuum, only pressure.

An unlit propnae torch will work though the idle will rise when you are close to a vacuum leak.

More than likely the IAC is the problem, and you can unplug the IAC and have the car not stall even if it's bad. I am not sure for the 97' year model, but on older IAC's that had the bellows and plunger they would usually get gummed up with oil from the PCV system that would cause them to stick and cause high idle and problems you are describing. The stalling is usually because the IAC will finally close and it's harder to open so it doesn't respond quick enough to keep the engine from stalling under the condition you mentioned (fast stop). The IAC is controlled by a PWM signal that the longer the pulse is on the farther the IAC opens, when it's not needed (like cruising) it has almost no signal to it.

Jeff
 

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Typical vac. leaks in the vulcan engine are the PCV elbow and grommet that goes into the valve cover, check that as well if your tracking down a vac. leak. My Taurus runs the same way if I unplug the vac line from the PCV valve with the engine running (Mine doens't leak unless it's unplugged.)
 

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Fast idle demons, at stoplight

My 98 taurus high idles sometimes at stoplights. And, when it's started cold or hot, it revs up to 2500rpm, then settles back down after about a minute.

I replaced the IAC not too long ago (two months) because of this idle problem, it seemed to go away for awhile, then it came back! I've replaced everything - the EGR sensor, valve, TPS, air temp sensor, MAF sensor, Trans Range Sensor, the works! If I unplug the IAC it idles down to 800 and stays there.

I also checked for vacuum leaks and changed plenum gasket. I'm stumped!

This is a really maddening fault and I hope someone can help me with it. It's especially dangerous when pulling into a parking space after driving a bit, you really have to fight the car with the brakes and pop it into neutral.

Please help! Thanks in advance,
 

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When you replaced the IAC did you clean the passages? If they are clogged then you have the problems you are refering to, you can also get crap into the IAC from not cleaning the passages causing what you are seeing too.

Jeff
 

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I removed the IAC I bought at CRAPA a month ago when this ordeal started. The plunger was STUCK. This thing was defective from the get go. I tried to move the plunger up and down and noted that it was sticky.

So, for 40 bucks I ordered a new one (and not the cheapest one) from Rockauto and installed it today. I chose the "original engine management" brand, as it says it is made in USA. It worked fine out of the box and it cured the problem! Car runs as smooth as the day it left the factory. Flawless.

So I feel stupid having changed most every other vacuum gizmo and sensor on the car. At least I can trust them now.

It goes to show you, "NEW" does not mean free of defect! In this recession I've noticed that I have had a higher instance of buying "new" stuff only to find that it's something someone else already returned! :angry:
 
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