325 M20 engine flatspot and "Hunting"

Over the last week, I replaced the cambelt on my M20 engine, as well as
disassembling the "fuel side" (manifold, injectors throttle body etc) to
clean it up and replace some cracked hoses etc. Now, after starting it
up, the engine is "hunting" on idle, has a flatspot on acceleration, and
is generally not running all that well (although still perfectly
drivable). My first thought was vacuum leak, but I have been all around
spaying carb cleaner on all the hoses and joints to try and pick up a
leak, but nothing.

The only other thing I noticed is that the black device near the top of
the inlet manifold (I think it is the idle air bypass valve), makes a
loud buzzing noise when the ignition is on, don't know if it is related,
as I cannot remember if it made this noise before.

Anyone got any ideas, would the cam timing being out by a tooth cause
this? Could it be the idle air valve thingy?

Any ideas much appreciated

Robert

Hello,

On my old '86 320i this also was a problem, I cleaned out the extra air
valve. You can also check if when the engine is heated up that this thing is
fully closed. At my car it was still a non electric one, it was closed by
the heat of the cooling system.

Did you also check the big (10 cm accross) hose between the air filter box
and the air inlet? At my car this one was cracked at the bottom.

Best regards,
Marcel, '92 525i @ 344.000 km


"Robert" <kosi (AT) ntlworld (DOT) com> wrote

Over the last week, I replaced the cambelt on my M20 engine, as well as
disassembling the "fuel side" (manifold, injectors throttle body etc) to
clean it up and replace some cracked hoses etc. Now, after starting it up,
the engine is "hunting" on idle, has a flatspot on acceleration, and is
generally not running all that well (although still perfectly drivable).
My first thought was vacuum leak, but I have been all around spaying carb
cleaner on all the hoses and joints to try and pick up a leak, but
nothing.

The only other thing I noticed is that the black device near the top of
the inlet manifold (I think it is the idle air bypass valve), makes a loud
buzzing noise when the ignition is on, don't know if it is related, as I
cannot remember if it made this noise before.

Anyone got any ideas, would the cam timing being out by a tooth cause
this? Could it be the idle air valve thingy?

Any ideas much appreciated

Robert