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Ted G.
Ted G., ASE Certified Technician
Category: Car
Satisfied Customers: 6138
Experience:  20 years auto repair experience, ASE Master Tech, Mechanical Failure consultant, Expert Witness
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2008 FORD TAURUS: I have a 2005 Lincoln Navigator

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I have a 2005 Lincoln Navigator and have had several incidences similar to(2008 FORD TAURUS 10240327 Consumer Complaints). Lincolons position is it either drvier error or the problem does not exist. I was wondering how the Taurus issue was resolved.
What type of incident are you experiencing?
Customer: replied 8 years ago.
Already Tried:
Auto surged/reved at least 4 times. The surge stopped when shift thrown into park. The surge occurred while stopped with foot lightly on brake. Took full weight on brake pedal to keep car from hitting person or car in front of us. Dealer and field engineer checked the car and claimed it was driver error(foot on brake and gas at same time) since they couldn't reproduce problem. Their position is," if it's a random/intermittent problem and they can't reproduce it, it doesn't exist". That's why I like to know how the Taurus problem with surge was resolved. Looks like I may need legal advice. - Bob
What we have seen on several of these is a combination of factors resulting in your symptoms. There is a part on the engine called an idle air control. It is basically an air valve that opens and closes under control from the computer to raise or lower the idle. Over time, from usage they will get build up in the unit and begin to stick. If the stick is intermittent then you will have an idle fluctuation only at certain times or temperatures. This sets up a surge scenario, because the idle will drop from a load on the engine, like the AC compressor coming on or the power steering pump loading the engine, and the computer will try to raise the idle speed. If the IAC sticks at that point the speed will not increase and the computer will command it to open even further. This happens approx 10 times a second so in a short period of time the IAC is commanded to open quite a bit. Then it comes loose and opens to the commanded position so a rush of air comes in to the engine. This causes the rpms to surge up. Now understand this is enough to make the car surge forward slightly if you are only lightly pressing on the brake. At that point it seems the driver reacts by pushing on the brake pedal harder and in some cases, we suspect, moving their foot somewhat to the right and contacting the accelerator pedal. At that moment they have become the reason for the unintended acceleration without realizing it. It doesn't happen to all people in all cars but the pedal placement on some vehicles seems to be more conducive to it. The physics of an automobile will not allow it to overcome the brakes with the engine so in cases where the auto actually takes off and runs into things this has to be the cause. Obviously it is not possible to see it actually happen but all the testing by the industry and investigations have never found a car that could accelerate past the brakes if they were applied and functioning. So after all that, how to solve your problem? I would strongly suggest replacing the IAC and then monitoring it. I suspect if the initial surge is cured, you should have no more incidents.
Customer: replied 8 years ago.
The first part of your answer is good info but the second part is the same position that Lincoln is taking(driver fault). We are 100% positive that our foot was on the brake and not touching the gas pedal. In the navigator even if we try to hit the gas while our foot is on the brake it is near impossible. Again the engine rpm tries to redline when the situation occurs. Can IAC problem drive the engine to redline?
Customer: replied 8 years ago.

Can I find out how the following complaints were resolved?

Complaint Number:10229836
Complaint Number:10208801

No, the orifice is only so big, usually if they stick open you will see 2-2500 rpms in neutral. Your description is different from some I have see in that you were able to keep the vehicle from moving forward. As you can imagine usually this involves a crash into something. I will never discount the fact that something else may be occurring since I am a firm believer in the fact that I have not "Seen it all". If your vehicle was slightly newer and had a "fly-by-wire" (electronic throttle) system then what you describe is theoretically possible since we really have no idea what the computer is commanding the throttle to do. (Frankly those systems scare me a little) But so far we have not heard many failures in that regard, even though the Taurus you referenced could be that. Where are you getting these complaint numbers from so I can do some research?
Customer: replied 8 years ago.

I got to you thru I thought you were tied into that site. The following is the taurus comlaint page.


The dealer gave me a long BS story about how fly by wire has redundancy and checks that "make what I've experienced impossible to happen". I have be lucky that I haven't hurt anyone so far.

We are tied to lots of sites and we have no way to know where a customer comes from. Sorry for the confusion. I also have to admit I grabbed some incorrect info on your truck during my answer. You are totally fly by wire and do not have an idle air control per se. All the functions are tied into the throttle body and computer system. That said it is possible that you are overcoming all the redundancies and the throttle body could be opening unexpectedly. Since it is computer controlled and we all know how well computers are programmed I think it is a little naive to say unexpected acceleration is not possible. The only saving grace is that the brakes will hold the car against the engine, but obviously it can still result in crashes, as the Taurus complaints alledge. BTW, those are NTSB/NHTSA complaints and are being investigated by those agencies. If they come up with a finding or resolution they should issue a recall. I realize that doesn't help your situation right now, but you may also want to file a complaint with them for documentation purposes.
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Customer: replied 8 years ago.

Thanks. I didn't find it earlier but I see several complaints of this nature on the Lincoln town car page.


I'll continue to dig into this and it looks like I need a lawyer to protect myself.