Hey,

The car has a subtle (low freqency) idle surge that only appears when the coolant temperature is at normal operating temperature. What could it be? PCV, throttle sensor, ICS, air leak... or *sighs* is the engine blown? I am afraid to drive it :- /

Car has a mazda rebuild with about 100 miles in it. Not sure if the car had an idle problem before the new engine as the car was bought with a blown engine. Seems to run well otherwise, starts fine, no oil or anything else amiss...

agh, please help

dave

 

Check all the hoses that attach to the intake manifold and the rats nest, check the manifold bolts are all tight and the thermosensors are ok. Check for error code from ECU. I assume the tach needle just goes up and down but by how much? Does it do it with all electricals off (fans,AC lights etc.)?

 

I will have to somehow check the error codes from the ECU, but so far it is not throwing any CEL. The tach needle goes up by mebbe 300 rpm, but it is hard to tell as the tach is unstable as well... Might be a loose connection or something more major, still unknown

When I last checked it was with the lights on, but i think it does it with the lights off (nothing running but the engine)

 

About 90% of the cycling idle is due to an intake manifold air leak. I heard that if you let out so propane around the intake manifold the engine will race a bit when ingesting the propane through a leak. But the exact procedure escapes me so DON'T try it.

 

ok sweet... basically i just hope that the engine is not blown... i have heard not such good things about the factory mazda rebuilt engines...

I will look for leaks tomorrow

thanks for the help

 

I'm experiencing the same problem...it surfaced after I put some mods on the car and did some hard driving.

I was told to look for a broken or disconnected vacuum hose but I have yet to find anything...I am in the process of checking the ECU error codes.

On a side note every now and then my temperature gague comes on and beeps at me for a minute or two (only after starting the car though, after that it is fine). The car tends to idle high after it warms up if there are not electronics on, once the lights come on or the wipers or anything that sucks some juice the surging begins.