Zafira 1.8 petrol 'jerkiness on light throttle problem' cure?

  • Thread starter Thread starter Mike J
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Mike J

My W reg Zafira has had light-throttle jerkiness for a while and it gets
worse as a yearly service draws closer. Last year they 'cleaned out the
throttle body' and it cured the problem. The cleaning was just a carb
cleaner spray! This year, the jerkiness reappeared and the throttle body
re-cleaned. This time there was no cure.

Given this I decided to have a go myself after reading about Vectra ECOTEC
cam cover breathing pipe problems.

Off came the air filter to throttle body ducting. I disconnected the
throttle cable to throttle body to get better access to the 2 cam cover
breather hoses that join onto the throttle body.

The upper one vents up stream of the throttle and was not blocked. The lower
hose (which vents downstream of the throttle and is thus more 'active' on
light throttle) was removed and dry dust came out!

Using a mirror and torch allowed me to that a small hole in the throttle
body was blocked. With my trusty paper clip, that had just flashed out my
self made EGR error code (see other posting), I opened up the small hole.

Subsequent journeys have had no 'jerkiness', although early days yet!

HTHs.
 
might be the icv as well

I am not sure the Zafira version of the 1.8 uses an ICV. All my info points
to an ECU controlled throttle stepper motor for idling stability, rather
than an 'extra air' system that can get blocked (like our Golf GTi). Note
the idling is fine.

If I am wrong, can you supply more info, so I can track it down?
 
Mike J said:
My W reg Zafira has had light-throttle jerkiness for a while and it gets
worse as a yearly service draws closer. Last year they 'cleaned out the
throttle body' and it cured the problem.
Click to expand...

I forgot to mention that they also upgraded the ECU software to the latest
version and this cured a stalling problem (only happened when aircon off!)
The cleaning was just a carb cleaner spray! This year, the jerkiness
reappeared and the throttle body re-cleaned. This time there was no cure.

Given this I decided to have a go myself after reading about Vectra ECOTEC
cam cover breathing pipe problems.

Off came the air filter to throttle body ducting. I disconnected the
throttle cable to throttle body to get better access to the 2 cam cover
breather hoses that join onto the throttle body.

The upper one vents up stream of the throttle and was not blocked. The
lower hose (which vents downstream of the throttle and is thus more
'active' on light throttle) was removed and dry dust came out!

Using a mirror and torch allowed me to that a small hole in the throttle
body was blocked. With my trusty paper clip, that had just flashed out my
self made EGR error code (see other posting), I opened up the small hole.

Subsequent journeys have had no 'jerkiness', although early days yet!
Click to expand...

The jerkiness has returned and I am now almost certian that it is the EGR
valve. I disconnected its electrical connector and the jerkiness disappears,
although the engine fault light stays on - of course.

IIRC, the EGR valve is used to reduce NOx. NOx occurs under high combustion
temperatures. High temperatures occur with lean mixtures. Lean mixtures
occur on light throttle. Today is a hot day. If the EGR valve lets in too
much exhaust gas (which actually reduces burn temperature!), then the car
will miss (I guess).

BTW, the easiest way of checking the lower cam cover breather hose is to
remove it at the cam end and, with the engine ticking over, feel for suction
on the pipe that is still connected to the throttle body. Air will probably
pulse out of the cam cover as well.

HTH,
Mike.
 
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