What causes the idle to raise when car stops - 1996 Mazda 626

How does it idle in park , does it run ruff or smooth? Are any lights lit on the dash , check engine etc. ? Could have a partially plugged IAC air passage .idle air control (IAC) valve ! The engine computer uses the IAC to control idle , when under a load such as when put into gear the computer raises the idle ! It does this by allowing more air to by pass the closed throttle into the engine raising the idle ! If these air passages clog they restrict the air flow an cause a idle problem ! Now if it runs ruff at idle in park you could have vacuum leak ! Rough Idle How to Fix Ford Taurus Engine Stalls at Stop Signs

have you fuel pressure check for steady pressure normally 45 to 60 lbs and steady not fluctuating.

The idle speeds software driven But vacuum leaks can raise idle speeds or weak mounts cause the shift in position giving you the jolt.

Possibly a fuel issue, but have the pressure checked before condemning the pump. Is the gas filter good? And the air filter?

It could be an idling issue-idle too low. Check if can be raised, or if idle control motor or valve needs service. Idle should be around 750 rpm, in drive gear, maybe a bit lower, not below 650 rpm, though.

probably cause by the a/c cutting in and out or running at idle . Fit an idle compensator to the system throttle or raise the idle speed 300rpm.

Problem on focus too . Without A/C on it idle's smooth . With A/C on the PCM - engine computer should raise the idle rpm. 850 . The only way to raise the idle would be to have PCM flashed programmed with up dated software . Adjusting the idle anyother way would cause check engine light problem , Wouldn't be able to get it to go out. Your best bet ,take it to the ford dealer and have the PCM reflashed .

What year and what engine size?

COULD BE THE IAC VALVE "IDLE AIR CONTROL".
LOCATED ON THE THROTLE BODY, TRY REMOVING AIR INTAKE HOSE AND WITH INTAKE CLEANER SPRAY OPENING AND ALL HOLES IN OPENING WITH CLEANER.VALVE IS STICKING AND RAISING IDLE. CAN'T HURT AND YOU GET A CLEAN THROTLE BODY SERVICE.

you could have a cylinder miss causing the comp to raise idle to try to stop the missfire. it could be a vacume leak or a bad idle air control motor. id check the throttle body for cracks and any vacume leaks at all. if your sure its ok,then an idle air control may be required

the idle speed is controlled through the on board fuel injection control module (known as the PCM), even if u raise the idle at the throttle body the computer will slow it back down, however there is a problem that causes slow idle, do the following procedure to correct the slow idle issue, follow it exactly.

Here are some of the causes of surges, stalls at stops, slow idle speed, erratic idle speed, rough idle and engine hesitation (and other problems), it is in most cases the idle speed control air-bypass valve and or throttle valve and upper intake, these area's get full of gunk and combustion residue over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.