Ok so I have this problem that I haven't been able to figure out. It started with me swapping over the motor into another car. I had forgotten to tighten the coolant hose that run to the thermostat and it was spitting out coolant. My car idle's just fine & steady at start up then when it's a little warmer the idle starts to drop to like 200 or 300 rpm stuttering then kicks back up to 800-900 rpm and will do that over and over.

So i tried bleeding the coolant by letting the car run and opening the cap to the radiator. I bleed and re-bleed over & over and still found that there were minimal air bubbles coming out. It would idle fine for a little while, then the problem starts again with the idle dropping.

I checked the IAC valve, adjusted the idle control screw on the throttlebody and still same problem. I am thinking coolant temp sensor defective? But the car runs and drives fine and doesn't over heat.

Any info would be appreciated...

 

Hey I have the problem after doing the a similar engine swap so If I figure it out I'll let you know!

 

You should use the bleeder screw on the thermostat housing instead of the radiator cap.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by aquabob89 &raquo;</TD></TR><TR><TD CLASS="quote">You should use the bleeder screw on the thermostat housing instead of the radiator cap. </TD></TR></TABLE>

The problem isn't air. Air will create hot/cold spots that will cause the idle to rise, then fall... It doesn't fit the description that he gave. Think simpler.

1). Check the timing, make sure its not horribly off
2). Disconnect the IACV. The car SHOULD idle at ~400rpms now. If it doesn't, you need to adjust the idle via the idle control screw. Plug IACV back in, restart car, problem solved (usually)

 

Replace your intake manifold gasket. If that doesn't fix it, make sure you don't have any vacuum leaks. A vacuum leak causes erratic idle.

 

you can use a dvom to check the sensor depending on what type 2,3 wire

 

I am having idle problems with my b16b. Once it warm up, it starts to idle low about 300-400 RPM and then back up to about 1500 then back to bout 800 RPM. It will keep doing this over and over again. I tried new wires, plugs, rotor, distributor cap, air filter and even checked the timing. Can a little to much coolant cause this problem.