i just got my newly rebuilt streetported engine in my car yesterday. it has an hks super mega flow, rb header, rb presilencer, jacobs rotary pro ignition pack, brand new injectors, and a rb street/strip clutch/pressure plate combo. everything else is oem. i have put 200 miles on it, but i have an idling problem that wont go away. here it is.

when cold, it starts great, but wants to idle at 1700 rpm's. i have to blip the gas to get it to drop. it still idles at 1200 rpm's after that.

when hot it idles at 600 rpm's (a little low), but takes a couple blips of the gas as the starter is turning to get it to fire up.

it smokes like its getting too much gas under acceleration (light gery smoke).

also it is running a little hotter. the temp gauge is at 50%, versus 30% with the old engine.

i talked to a trouble shooter from the saturn plant today about general engine theory, and he suggested replacing the engine temp sensor. does this make sense?

 

Yes, in our cars it is referred to as a water thermosensor. It is plugged into the back of the water pump. If you motor was just rebuilt and it only has 200 miles, then it is still in the break in period, so things like hard starting are to be expected.

Check your ECU for error codes.

 

doesn't the ecu only generate error codes when the check engine light is on? that is what i have been told by my local mazda daeler.

 

If the check engine light is on while the car is running then that means the ECU has an error code.

I'd post the error codes and the directions, but I uh, I kinda lost them.

If your check engine light is definitely on, find the codes and run the check. Chances are if it is coming on something is merely unplugged, loose, or not connected properly. If it's not coming on, the ECU sees everything as working the way it should.

As for the idle, wait for it to be broken in and see what it does as far as starting. The way you described it, it sounds fine to me. My prefered idle speed is 600 RPM's anyway, but that's just me.