Engine surge I was coming to a stop light on a busy road and had my foot on the brake. The engine surged almost 4k rpm's and almost made me run into the car ahead of me. I had to stop the engine to get this to stop. This is a 2006 sonata Hyundai 3.3 ltr engine. please help

test the brake booster by idling the engine with out the foot brake applied then apply the brake
if the fault appears with the brake applied ,replace the brake booster.

Hi Wendi:
If the engine runs fine except when you don't have your foot on the gas, maybe the idle stop needs to be adjusted. With the engine off, have someone step on the gas pedal while you look at the linkage at the carb. There should be a plate with a screw in it that keeps the butterfly valve from closing completely. This can be adjusted with the engine running. (SAFETY FIRST - MOVING PARTS CAN BITE)
If the engine will only run at not nice too high RPM, chances are that the idle jet in the carb is plugged, and a carb cleaning and possibly overhaul may be needed.

Is the car equipped with the Automatic Transmission?
If so, read on.
Otherwise skip to the end and answer some questions.

POSSIBLE SCENARIO:
I have observed a condition where my car surges slightly when the torque-converter clutch (TCC) cycles between lock and unlock when driving on an uphill grade.
First some basics and history that will explain why the TCC is used.

Engine, Torque Converter, TCC, and Transmission relationship--
The TCC allows for a solid connection between the engine and transmission which allows the input to the transmission to rotate at the same speed as the engine.
Without a TCC, there is slippage between the engine and automatic transmission. The slippage is greatest at low engine RPM. That is what allows the engine to run with the automatic transmission in gear, like when you first shift into gear or stop at a stop sign. When the throttle pedal is depressed, the engine RPM begins to increase and the torque converter begins to slip less and less the more the engine RPM increases. The car moves. But even at cruising speeds the torque converter slips slightly. Engine RPM is greater than transmission input RPM, which is realized as slight decrease in fuel efficiency.
When acceleration is complete and a constant speed is being maintained, the engine power output is reduced to the point where the TCC can engage and eliminate any slippage between the engine and transmission. If the car has a tachometer the engagement of the TCC can be verified when a slight reduction in engine RPM observed without a corresponding change in vehicle speed.
One method used to test the operation of the TCC is as follows:
Find a flat section of road where it is safe to perform the test.
Reach a steady speed and keep the gas pedal depressed with one foot. While observing the tachometer (or listening for an increase in engine RPM), with the other foot depress the brake pedal enough to activate the break light switch but not enough to engage the brakes. When the brake light switch activates, the TCC receives a signal to disengage. With the gas pedal being held steady, release the brake pedal and the engine RPM should decrease when the TCC engages.
Old cars with Automatic Transmissions did not use a TCC. I believe the TCC was put in use in an attempt to increase fuel economy.

MY EXPERIENCE WITH SIMILAR SYMPTOMS
The condition that causes that issue on my car is this:
- A slight uphill grade increases the load on the engine.
The car tends to gradually slow and it is necessary to depress the gas pedal to maintain speed.
- Depressing the throttle pedal (manually, or automatically with cruise control engaged) signals the torque converter clutch to unlock when the load increases slightly. (A more drastic load increase would signal the Transmission to downshift to a lower gear.) The corresponding increase in engine RPM and output is enough to compensate for the reduction in speed. When the vehicle speed, engine RPM, and throttle position stabilize to the point that the TCC will engage and the engine RPM will reduce in correspondence with TCC engagement. Now, if the road conditions have not changed, power output is not enough to maintain vehicle speed. With the increased load caused by full engagement between engine and transmission, and the cycle (surging) repeats itself until the road conditions change.

Does that help?
If not:

QUESTIONS
Please define the symptoms.
What are the road conditions when the surge occurs? (A slight uphill grade?)
What is the frequency of the surge?
Does the engine power output have a noticeable surge?
Is there a speed change related to the surge?
Does the tachometer move up and down with little or no change in vehicle speed?
Are all instrument indication in the normal range?
What else has changed?

Good luck!

Crank shaft sensor.

maps sensor

check the swiches at the brake pedal their should be two. one for brake lights and one for transmission dump valve it prevents the engine from loading up at lower rpm. ie stoping at lights while in drive

I was kind of surprised to see your post, I have not run across this problem in my shop yet, maybe just demographics. 1000. bucks to do this job seems high, maybe shop around. I did a little checking on the net and it does seem to be common. I found a very good article, even if you don't want to do it yourself, it may give you some ammo, and help you understand what's involved.

http://volvospeed.com/vs_forum/index.php?showtopic=101431

Sounds like a bad IAC (idle air control valve/sensor) that controls your idle when going from throttle to idle. If bad your idle will act crazy and can cause stalls easily. Pretty sure that's it.

this car must be under the factory warranty.
take it in this car is unsafe to drive

You could try disconnecting the air valve and see what happens.The car may stall when idling if you turn on the air, just set it to idle high and leave the air on all the time :)
Keep me updated man

regards
robotek