the idle is not 'terribly' rough, just not as 'smooth' as it should be. I note
that the rpm under load (after the car is warm) when idling drops to just above
500 and increases to just short of 700 in park. I've changed the distributor
and rotor of course, wires appear good (although not new) and I've changed
the O2 sensor (hurray it passed emission with flying colours then) I just
for the world can't figure out what might be causing this 'uneven' idle which
is actually noticeable in terms of car vibrating a tad.
What am I missing? anyone have any pointers?
-->> T.G. Lambach <<--" <"T.G. Lambach at NoHamorSpamcomcast.net"> wrote:
1) relatively new, <20k km
2) all read 2k ohms (ie 2x 1kohm)
3) good point, I sprayed propane all over the engine compartment while
the car is running, no change in idle..... I was hoping I'd hear something
ps will recheck all the above again
Hi, that's the 'bypass' valve to set air/fuel mixture right? Took it out
and cleaned it, checked it by connecting power to it directly and it
Yes, got to check all the vacuum hoses again.... it 'must' be that, but
I 'have' checked them.... maybe I'm missing something.
thanks and cheers
Go to autohausaz.com to look at the picture of the part.
Wires at 2K ohms are bad... they are supposed to be 1000 ohm and 1300 ohm at
the most before you will start misfiring. Measure the wire from the
distributor to the spark plug.
On Jul 31, 3:52 am, email@example.com (Guenter Scholz)
I would also look for vacuum leaks as the first thing, around the
"bypass air valve" in particular (higher probability and larger impact
than other places).
As I remember, you have tried to trace this problem for a long time,
Have you compression tested the cylinders (engine requires correct
mixture, ignition and compression/valve timing... you have already
been tracing first two things quite thoroughly)?
If a valve does not operate correctly, it could cause uneven running
of the engine - not only in idle but it would probably be most
Or if the engine is running smoothly but still vibrating, it could be
as simple as the engine mounts.
Jens, all good points. Yes, I've been trying to correct the situation
for some time. Putting in new distributor helped noticeably in that the
engine now does not stall anymore. I will definitely check the compression
in each of the cylinders. But I guess my main thought is still with the
bypass valve because only that could cause an rpm shift between "D" and "P"
ie, in park it idles at near 700 rpm and in D it's more like 500 rpm. This
is after engine is warmed up. When engine is cold it idles just fine at 700
other than the occasional hic-up - ie miss - in both P and D.
On Aug 3, 3:02 am, firstname.lastname@example.org (Guenter Scholz) wrote:
Just a thought:
Bypass air valve (also called idle speed actuator) is in fact at small
ecu controlled throttle in parallel to the main throttle, and gets
likewise air through the air mass sensor. The ecu should control the
bypass air valve for constant idle speed. As I remember, you already
tested the variable duty cycle signal to the bypass air valve, meaning
that ecu is trying to do its job.
Check again the hose from air mass sensor body to bypass air valve. If
false air is drawn in here, it would give symptoms as you describe....
ecu will control the bypass air valve to deliver more air to increase
idle, but air mass sensor will not messure the extra air and provide
fuel accordingly, causing too lean idle mixture and rough idle,
particularly when engine is slightly more loaded in D.
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