I read on another post that some had removed their cone air filter and covered the maf a bit and the idle settles down.

 

So i tried this last night, i covered half of the MAF with my hand, and it DOES settle down. If i cover the whole MAF it obviously stalls.

 

One thing i did noticed too, is the when i cover half the MAF, the revs increase oh so very slightly. this could be mistaken for it settling down, because my car sounds fine above 1500 RPM.

 

Why does restricting the air flow to the MAF settle the idle down, increase the revs slightly and stop it chugging?

idle control valve upping the rpm to stop it stalling due to restriction?

Not sure m8, any techies arround that can clarfiy?

The afm works on a hot wire system, there is a fine wire sensor that is heated by a stablised set voltage this draws a set amount of current for a given amount of air been drawn passed it, as the air been drawn past the sensor cools it down it alters the amount of current the fine wire draws from the circuit, this is how the calculation is made for fuel / air ratio.

 

By placing your hand over the end of the maf, the amount of air is reduced so the fine wire starts drawing more current, the signal now tells the ecu less air is been drawn in so it fuels accordingly BUT it also knows the throttle is closed because of the tps position, so to prevent stalling the timing will advance slightly and the aux air will open slightly.

 

The increased stability of the engine is then just a consequence of attempting to fool the system, it does not represent any cure or any hint of why any particular engine is unhappy at idle because the moment the idle speed is raised by the ecu you have moved out of the problem zone ( rough idle )

 

Most idle problems are connected to air leaks, poor sensor connections, poor throttle balance, poor base idle set up, faulty aux air valves,faulty afm`s and timing issues all of which can be sorted very , very quicky with a ConZult.

 

Hope that helps

 

Jeff TT

Edited January 3, 200916 yr by JeffTT

Perfect response again Jeff!

 

Thanks