406 V6 3.0 lumpy tick over

Hello All, My 406 3.0 V6 seems to idle in a lumpy fashion. With all the electrical extras off i.e. lights, fans, heaters, AC and the steering wheel not moving and foot off the brake: The cars idle speed fluctuates, well more dips occasionally. Not periodically but every 20 seconds or so. Most of the time the car recovers, it seems by applying is own amount of throttle. Other times it stalls (particularly when facing down a hill or approaching round-abouts). When you put your foot lightly on the accelerator to take the engine what would be 1000RPM the engine actually fluctuates between 600RPM and 1100RPM. Kind of like it is an unstable system with to much overshoot. Other than that it works flawlessly.

I have had the coil, spark plugs and leads changed to no effect. I have had the ECU log monitored over the period of a week or so but nothing is coming up at all. I am guessing that this is a sensor that is not reading correctly.

Does anyone have a copy of a system diagram or can tell me what sensors effect the idling speed ? Or know of if this is a common fault? Does anyone else's V6 not have a rock solid idle speed?

Regards

Gary

Reply to
G Cadman
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Reply to
G Cadman

This sounds a lot like the old idle-speed stepper motor problem. I've had that problem with those exact symptoms on other motors, but have no idea if the V6 406 suffers with it or even has one.

djimbo.

Reply to
djimbo

I've had the same vehicle - 3l V6 - for years and I have noticed, when idling, that it occasionally gives itself a touch of the accelerator. Or that is what is feels/sounds like.

I assume it is an artifact of the engine management system and serves some purpose. It has never bothered me - nice to think that the engine can look after itself.

Reply to
Ken

I had one too for 8 years (new in Feb '98) - automatic - and it did the same. Early on it started cutting out intermittently when slowing to a stop, like at lights or a junction. Can't remember now the exact details, but I

*think* it was fixed by fitting a new engine management chip or something. I also have some recollection of it being covered by a Peugeot recall, but I may be wrong. Anyway, after the fix it was fine, but always did this slightly irregular idle.

-- Tony T In email address NNNN = 7 x 643

Reply to
Tony T

Do you know where this is located? Unfortunately they don't do a Haynes manual for the V6 engine.

Regards G

Reply to
G Cadman

I had a similar problem on my 406 HDI, turned out to be the lambda sensor. I think this lies in the exhaust path and detects the amount of oxygen in the exhaust and adjusts the fuel mix accordingly. Once this was changed I had no futher problems.

Neil.

Reply to
Neil

How much did this sensor cost? If you don't mind me asking?

Regards Gary

Reply to
G Cadman

I have a 3.0 V6 Auto. Like Ken's, it does occasionally "give itself a touch on the accelerator", but your problem is MUCH more significant than what happens with mine. If you spend a lot of time in traffic, I should think your fuel economy is suffering from this too.

Reply to
Fin

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