Hi,

Thanks in advance. 2006 Mazda 6 2.3L 5Speed.
Wondering if someone might shed light on this problem and suggest things to try. When I start it cold in the morning and stop at the first intersection in Drive the idle is annoyingly low and bounces a bit. Putting into Neutral raises the revs to a sensible level and stops the bouncing. The car also does this when right up to temperature - idles too low - again putting in neutral helps/fixes it.

I'm led to believe that an intake leak tends to puch revs higher whereas mine are dipping too low. Doing an ECU reset (disconnect battery for a while, then idle for 20mins) fixes the problem for about a week, then its back to the same issue. I haven't asked my mechanic to look into it but he told me that it is throwing no codes.

Thanks,
Simon

 

Get your throttle body & MAF cleaned.

 

Hello again grim! (You helped me before in these fora when I first bought this car 4 of 5 years ago! And I'm also in NZ). I haven't done the MAF but I have cleaned the throttle body - maybe I'll do the MAF if the problem isn't solved. I'll put pics below. Judging by the condition of it you might be right/have solved the problem.
As stated in the OP whenever I reset the ECU it gets better for a while, so I'll know in a week if it has solved the problem. But already it drives perfectly. One thing that is noticeably better is that I'm sure there is a little slack in the drivetrain - I think the gearbox somewhere as there is a perfectly reasonable amount of slack when I rotate the wheels when up in the air - which is most noticeable when going from slight engine braking to on throttle and vice-versa. This feels way better now, I think because when off throttle the engine isn't trying to idle so low.

One question I have is, how in the sam hell does carbon build-up occur in the engine intake. I mean, it's the intake!. Before engine filter, no problem. After filter, no problem. MAF sensor, no problem, Rubber duct to throttle body, no problem. Throttle body and south, problem!

 

Interestingly some tarnishing on the intake side did not come away. I would have thought the opposite would be true, but maybe the carbon build-up actually protects the engine-side surface from....windage damage, maybe. I also thought that when cleaned the butterfly might sit completely closed, but this did not happen. Obviously it is designed to be slightly open when 'closed'.

 

It's been over a week and still running very smooth. I call this a win. Thanks Grim!!