Not sure what to put in the title but here is my daughters problem...

2003 Taurus SE 3.0 (OHC) engine. The car idles fine when in park around 700 - 800 rpm. When you put the car in drive you need to be pressing hard on the brake or the car will move forward quite strongly.

I think when you put any car in drive and let the foot off the brake it really shouldn't move at all - especially on a level surface. But there is obviously a higher load on the engine when in drive than in park so what controls the engine rpm when you do this so the engine wouldn't stall.

Am I wrong about this acceleration from the car when no foot on the brake or accelerator?

 

Forgot to mention that the check engine is not on so I haven't bothered to see if there are any DTC codes generated. Could there be some if light is not on?

 

It depends how much acceleration and if it is after cold start or when warm.

At a cold start the idle is raised so much (about 2000rpm) that the car could go about 50 mph.
When the engine is warm the idle should be about 800 to 900 rpm. shifting into gear will raise the idle a little bit and should, on even ground, induce a very slow roll that is easily stopped with the brake.

So is the problem occuring when cold only?
Does it occur when cold and warm?
Is it less a problem when warm?

 

It happens when engine is hot. Drive around come to a stop sign or light. Put foot on brake - car stops. If you let foot off brake then the car will take off on you - not just roll forward a little bit.

 

It could be a stuck throttle cable.
It could be a dirty IAC valve:


It could be a number of other things. But these are the first ones coming to mind.

 

Nice suggestion you have given and also you have shown the image so clearly, now there should be no ambiguity for the problem. And most of problems of this type occur when the engine got heated.

 

Sorry for the delay in responding. I have been focused on the other issues with this 2003 Taurus 2003: new starter, jammed rear electric window, putting a new radio/cd player in to relace the factory one. Who the hell dreamed up putting the radio/amp in the trunk, running cables to the trunk and leaving tons of space behine the dash for a radio. There has to be some logic behind doing this????

I did remove the IAC and cleaned it out and lubed the throttle cable mechanism but it made no difference. I dismissed the IAC as it appears to do what it is supposed to do. From cold start engine rev's high for a bit and then in stages slows down and finalling idles at around 700 -800 RPM. All appears to be ok. But put it into drive then idle realy doesn'r rev much higher but let of the brake it will accelaerate quite alarmingly.

As the IAC is around $50 in Autozone I should just switch it out.

 

my 2006 holds just fine when engaging drive at higer rpm than 900. If all else checks out; what condition are the brake friction material in?

 

I have the exact same problem on my 2000 Taurus. Same engine as well. I changed to IAC, it did not fix the problem. My car also has no engine light. The car runs fine, but it will accelerate all through the gears, and takes a moment once you apply the brake for the RPMs to begin to drop. One you take your foot off the brake it begins to accelerate again. I have cleaned the throttle body, and done an extensive search for leaks. The car idles perfect until you put it in drive, then it takes off slowly accelerating.

 

That makes me think that there is an issue with the PCM or a sensor feeding wrong data. I hope someone with more experience will chime in.

I would first disconnect the pcm harness and inspect it for corrosion. Inspect and test the throttle position sensor. I am at the end of my wits.