"Comboverfish" > wrote in message
oups.com...
> Your 2.4L has an EGR valve that feeds exaust gas to all four cylinders
> individually via cast runners inside the intake manifold. When some
> but not all of these runners clog up, the remaining open runner gives
> all of the exaust gas to it's cylinder. This results in a small
> misfire or stumble only during EGR operation. The EGR valve doesn't
> open at idle; it starts to operate off idle from approx 1500 RPMs and
> higher during light to moderate load conditions. If those conditions
> match your car's hesitation enabling conditions, then we're on to
> something.

Well, it happens right at idle, and above 1500 RPM I can't really notice it
at all.

> To see if this is your problem, simply remove the vacuum hose from the
> EGR valve and test drive the car to see if the problem has disappeared.

Sorry, I actually already tried this, and no change. The one thing I've
been wondering is if there's any way the exhaust gas might be getting sucked
into the intake in the space between the EGR valve and where it mounts, but
there should be less vacuum there when I open the throttle I would expect,
and if at idle it was pulling exhaust in there it would likely run very
badly.

I suppose it's possible the EGR valve is leaking enough to allow the exhaust
in even without the valve opening, but I've had it off and cleaned it, and
tried blowing into it, without any leaking. I wanted to disconnect the pipe
that feeds the exhaust into the valve, but it seems to be quite well fused
into the exhaust manifold.

> To repair this condition, you will have to remove the intake manifold
> and find and clean these runners with some sort of flexible pipe
> cleaner and carburetor cleaner. If your manifold is a two piece design
> you may be able to remove just the plenum and get to the passages that
> way.

It is a two part setup; I'll take a look to see what might be involved in
getting it apart, although it doesn't seem like this would be the problem in
my case. I wasn't aware there were separate passages for the EGR system
though, that's good to know.

> As far as the high idle goes, it's most likely a vacuum leak such as
> the PCV hose, brake booster, etc.

I've looked, but haven't been able to find any leaks. I pressurized the
throttle body/intake manifold by sealing off the intake hose and blowing
into the idle bypass hose, and there was no leakage. Right now I've got the
idle "adjusted" with a rubber o-ring in the idle bypass tube that restricts
the idle air. And no, it makes no difference to the off-idle hesitation.

Thanks for the reply!