Unexpected acceleration

I have a 2003 Mazda MPV minivan with 100,000 miles on it. Twice in 2 weeks it surged ahead just as I was coming to a stop in a parking place. Both times I had my foot on the brake and was almost at a complete stop. The car leapt forward about 4 feet each time and stopped as I stepped hard on the brake pedal. Our mechanic could find nothing wrong. Now I’m afraid to drive it

If I trade it in or sell it, I would disclose the problem, but how can I insure that it won’t be resold “as is” ?

When you say it leaped forward, did the engine speed increase and it overcame your brake or did your brake pedal just felt like it went to the floor and the car just rolled forward.

The engine speed increased and van lurched forward, but stopped quickly when I stepped hard on the brake and the revved up engine sound went away. The overdrive was not engaged, but the sensation was similar to the resume speed acceleration with overdrive.
Appreciate any ideas you have .

Sounds like an issue with the idle air control. When you sell something though you lose control and have no more rights to it. So if you trade you have no say in what happens to the car. The only way to control it is to have it crushed now without trading it in.

Sounds like a throttle body and/or Idle Air Control valve problem to me. They’re essentially one unit and a thorough cleaning after removal could help.

If you trade it off and are honest with them about the problem that car will end up in the hands of someone, somewhere. It’s possible that whoever takes it in trade will attempt to resolve that problem but that all depends.

Louise, you could take it to your shop and get an estimate for cleaning the throttle body/IAC valve as suggested above. Tell your mechanic where you got the information from, and show him the responses here. There are some outstanding mechanics here, and you’ve just heard from a few of them. If it doesn’t cost too much, it would be worth it to see if it solves your problem. Then you won’t have to trade or sell the car at a big discount because it has an unsolved unintended acceleration problem.

I’m a retired beauracrat not a mechanic so don’t include me in the “outstanding mechanic” class.

No offense, Bing, but I was really thinking of OK4450. But your sharp, even for a bureaucrat.

Two possibilities come to my mind. One is simple driver error, in which case you would accidentally step on both the brake pedal and accelerator at the same time. No need to be offended or embarrassed if this is the case, many people have done this before, including me. We even had a thread on here a year or two ago in which the original poster was prepared to sue the pants off the company who made their wife’s car when it went roaring backwards down the driveway, across the street, and into their neighbor’s garage (or something like that, it hit something) “on its own”. Some 20 or 30 comments later, the OP reveals that wifey has a medical condition that causes loss of feeling in her feet and legs, and that it was probably her unknowingly stepping on both the brake and gas and causing the accident. This kind of driver error does happen from time to time and is often attributed to a mechanical problem.

The other possibility is a mechanical problem. In addition to the possibilities mentioned before, I suspect you could possibly have a malfunctioning power brake booster. The brake booster is driven by engine vacuum and can possibly fail in such a way that vacuum can leak at certain points in the stroke. Engines respond differently to vacuum leaks. Some can stall, some can run rough, and others can positively scream in response to a significant vacuum leak. I once forgot to reconnect a brake booster vacuum line, started the engine, and it fired right up and immediately screamed up to 5,000 rpm, so this is a possibility.