oscillating RPM & motor choke

[Kumadov]

First of all thank you for a great forum for Peugeot 406 owners.

I own a Peugeot 406 SV petrol 2L yaer 2000 with 188,000 km.
when i start the car after a long period of time (more then 8 hours) the car starts and have oscillating RPM after a few seconds it is choked and shutoff. it is happening each morning even when it's not cold. If I push the accelerator pedal during the choke of the motor, the RPM are going higher (obviously) and after several seconds i live the pedal the motor will not shutoff but the RPM is still oscillating. the oscillation will repeat itself every time the car stops\stands (in a traffic light for example).
I've have read the article in this forum "FAQ - 406 D8 petrol (Excl. V6) running and starting problem" and changed the steeper motor part, did the reset (turn the key to 2 position for 30 s the off ffor 30 s X 3 times, then start the car and drive it for 20 min).
Well, now the oscillation is a little less BUT is definitely still there

Do you have any suggestions of what should i do next?

[steve_earwig]

Is it ok when it's warm? Can you have any diagnostics done? [/clueless but would like to help]

[Kumadov]

Hi,
RPM oscillating when car is hot as well as in cold. computer of the car indicates every things fine.

[steve_earwig]

I've been doing some searching, viewtopic.php?f=1&t=4841&p=47381&hilit=hunting#p50155 this looks like a similar problem, I'm wondering if the reset problems could be the same (anyone?)

[8Jb9]

A friend with a 1.8 petrol had an issue very similar to this. After replacing various parts, checking diagnostics, etc it turned out to be a vacuum leak from a hose to the manifold.

His list of symptoms, check to see if it matches:
* Oscillating rpm (similar to wave interference beats) occurs only in idle.
* if beats got bad rpm would drop below 500rpm and check engine would turn on until ignition was turned off. could sometimes stall
* If idle is held manually by throttle the rpm remains constant (if foot is steady)
* if high idle is held manually the ECU would eventually drop to low idle regardless, presumably by controlling it by super-lean fuel instead of ICV
* when dropping from high idle the rpm would "bounce" on the way down
* pp2000 revealed a fuel mixing-fault.
* pp2000 showed the ignition advance oscillating wildly in idle. manifold pressures, lambda, etc looked normal.
* symptoms happened both cold and hot.

i have a 3.0 V6 (J4, not J4S) with a slightly broken vacuum hose. it has developed *some* of these symptoms, but only to a small extent.

so... since your symptoms include completely stalled engine it could perhaps be that you have an even more severe vacuum leak?