Why would a car run in park but stall in gear?

The first thing I would check is the idle speed, second thing I would look (and listen) for is a vacuum leak, these are the 2 most common causes of your problem. Bill Alley

Check the plugs to make sure they aren't fouled. Then maybe the fuel pump. If it dies when you hit the brakes, that's electrical. I'd say it's the fuel pump, filter, etc.

When plugs are fouled, it probably wouldn't want to start, and brakes aren't electrical and the fuel pump isn't real likely either. Or maybe it ins't any of these, may want to look further down the list for a better answer.

Actually when you step on the brakes, it takes power from the battery or alternator to run the pump for the master cylinder on the brakes. (not true)

Doing so will cause your car to stall if the idle is too low. Turn the idle up and see if it happens again.

Same thing with the in gear driving. Putting the car in gear will drop the rpm to half or less than what it is already. Or maybe there is a better explanation down below.

The brakes have no pump. If they are power brakes, then it has a booster (and the booster uses engine vacuum, not electrical power) you can't adjust the idle speed in a FIed car. When you put the car in gear, the rpm should stay steady since the FI system should adjust for loads on the engine (turning the a/c on, putting car in gear, turning on lights etc) Do a tune up and go from there. By the sounds of it though, this is a lock-up torque convertor problem. The convertor lock is stuck on so the torque convertor is "solid" when you put it in gear.

If it is not an engine problem, it should be a problem with the transmission. When the gearshift is in drive, in this case, the gears get jammed with each other, causing the whole engine/drivetrain to lock up, stalling the engine. You should get a repair as soon as possible.

I know this sounds dumb,but i had a firebird that did the same thing in my shop & the only thing wrong was somebody put the wrong Tail light bulb in the socket & then forced it in wrong so when the brakes were applied it back fed the ignition system & killed the motor-It turned out 2 b a easy fix because I noticed the front running lights would come on when the brakes were applied when it pulled in 2 the shop.

I had that happen to me with my 86 Grand Am, it turned out to be a PCV valve, which was very cheap to fix...you could also try that.

It sounds like something I have been going through, In my case the car has an automatic transmition and the "Lock up celenoid" is the culpret. This little item (costs about 40 bucks give or take) is located in a ussually easy to get to area In my ride it is there right after removing the Trany pan.

What this thing does is causes the Torque converter to "Lock up" to the drive shaft - ussually in an overdrive type thing. When it gets stuck your car will stall.

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The fixes that where suggested to me where replace the celenoid or try to use fresh trany fluid ( for a short term fix )

Later! hbooker

check your fuel filter & fuel pump/pressure...........also, once you put it in gear it puts a load on the engine, faulty igniton wires may start to "arc" once the load is on, it will cause engine to run like s***t or even stall completely...

Have a 95 Barina C14NZ with auto tranmission. Drives fine, idles fine, but when it is put into gear it stalls. Traced fault to temperature sensor connector (the one for the computer at the back of the manifold -- not the fan one at the radiator). This connector had some minor corrosion which increased the resistance and hence told the computer that the engine is cold, even when the engine was at operating temperature. This caused the engine to idle a bit higher, so when it was put into Drive or Reverse, it would cause the transmission to grab and stall the engine. Wriggling the connector temporarily fixed the problem; and replacing the temperature sensor was the final remedy. Good luck trouble shooting! :-)

I have 93 New Yorker - Car ran fine in park, but any other gear and it stalled. Believe it or not the black box (with the keys) had batteries that were dead. It had to do with the car alarm - New batteries, car runs fine in all gears. You could give it a try.