rpm bouncing?
 

recently when i started my car and let it idle for 20 second, the rpm gauge would bounce up to 3k and down to 700-800rpm. then it would just bounce up and down, up and down like the motor is gonna die. any help on this? suggestion?

I usually only post in the 2nd gen area but I saw your question from the main screen... I would check the TPS...

Try starting the car in gear w/ foot on the clutch. This will disable the AWS Accelerated Warmup System. (Usually let the car run for 15 to twenty secounds before taking the car out of gear.)

If the car still feels like it wants to die check for vacuum leaks. Most common is the crossover pipe off the turbos.

I just saw your other post concerning not idling below 1200 or a 1000. Check your thottle cable make sure it has the proper slack, and also check that your fast idle cam is dis-engaging. Its located on the thottle body between the fire wall just below the wax rod under the throttle body coolant line. Mine was actually catching on some other linkage.

Check the hose to the map sensor

check out the TPS. tune it w/ a voltmeter.

Crossover pipe off the turbos would NOT be a vacuum leak as it is before the throttle body. A vacuum leak will normally produce a high idle, not bouncing rpms. Definately start with the tps and asjust it per the mazda manual.

+1, i agree

Very common mishap. symptoms include rough/choke idling with black smoke from exhaust. check the map sensor (firewall side near driver). if it's unplugged (can happen if you're working in engine around that area...I would reconnect and zip-tie that sucker.

Also check your grounding points. They may be nasty dirty. My idle was AFU and it turned out to be a broken ground wire.

How Does The Map Sensor Look Like Anyway To Be Curious? And Also The Tps?

its the idel screws next to the throttle body, adjust them a bit to the stock idle at 750, and the 3k rev at start up is normal on USDM cars, its an auto-warmer.. it helps warm the car up faster.. not a problem.

i check the voltage of my tps and find it off by .02...is that good or do i need to adjust it more?

off by .02 on which setting? Damian had a good write up on that if you want to search for it. Link to it is also in the FAQ sticky above.

Another thing to check is the mechanical settings (screws) on/under the throttle body. Mechanical settings will throw off the TPS settings.

did you change anything before this started happening?