Hey all, my 323 is having a bit of an issue, when I am going down hill around 50-40kph with no throttle the car slightly surges randomly like your giving it ever so little gas briefly. If I turn off the ignition while coasting downhill the surging stops, key on and it starts again, it is random though you might go 3-4 seconds without a surge then you get a tiny buck, it feels like a miss on accel would feel, just that little blip of power in my case. Any ideas? Only thing I can think of is either my IAC is going out or I have a leaky injector.

 

What do you expect out of a 15 year old car! Perfection!

 

Well if it had what your first pic has (fire under its a**) then it would at least be quicker :P

 

My first thought: vacuum leak.

....or your chickens finally hatched ;-) (inside joke)

 

Bahaha, funny, very vunny I did think of that but its down the list of things it could be although for the sake of really ruling it in/out doesn't the ECU turn off fuel on decel? If so a vac leak wouldn't show up since there is also no fuel to burn correct? If it was a vac leak it still should do it when the ignition is turned off on decel but it doesn't..........or am I missing something here?

Also the eggs haven't hatched.........yet, but I cant see the coolant pipe and radiator lasting too much longer although its lasted since April when I used them.

 

I think you are experienced enough to find a vacuum leak if there is one. Back from my motorcycle days I recall that a leaning out of the mixture causes a rise in RPM.

I don't know if the ECU completely turns off fuel delivery on deceleration. Complete fuel shut off could cause some rough running.

When you turn the ignition off, lets say downhill but in gear, then there should be no spark and no combustion. There still could be some fuel delivery though if the fuel pump is active. But I am not sure because I don't play with the ignition switch when driving.

Maybe a look at the spark plugs reveals something? i am just shooting in the dark here.

 

Plugs are new since the cylinder head change so they look clean right now, fuel pump turns off when ignition is off BUT not to steering lock, and we have LOTS of downhills LOL. I did a test on the 3 and it seems to do a complete fuel cut since the feeling going downhill is the same.

 

All I can think of is this: the fuel system is still pressurized when you coast and there could be a slight leak in the injectors. To test go coasting on one really long downhill.

 

Well I did the really really long hill and it has the surges the whole time with the ignition on, with it off its smooooooth. Very annoying riding in a bucking car going downhill, works fine everywhere else, just a bit smokey now at startup (black), ignition parts are new (cap, rotor, etc) since the head swap.

 

I would think this means it gets fuel when it shouldn't. Probable causes:

-Leaking pressure regulator: if the membrane is on the fritz it may leak an amount of fuel into the vacuum line and from there it goes into the intake manifold affecting all cylinders. Check fuel pressure, take the vacuum hose off and smell for fuel.

-Leaking injector(s). This will only affect the cylinder(s) where the injector(s) leak(s).

Also possible but not likely: the chicks feel the loss of gravitational forces on the decline and instinctively flap their wings which you feel as a power surge!