Idle and vibration S1 Xantia 16v

[davidc]

Hello
My S1 97 16valve Xantia petrol has a lumpy idle and there is an associated vibration through car which I can feel sitting in the drivers seat. Checked the exhaust system for binding and all rubber hangers, all appear ok. Think the engine mounts are ok - rev engine, engine doesn't try to escape out of engine bay. Changed plugs, air, fuel filters, cam belt but made no difference. Have to say that once underway it goes ok but does feel like it has a flat spot when at cruise but goes quite hard when floored (well it accelerates harder than my S1 8v!.
Any ideas of what could causing this(these) problems?
cheers
David

[Clogzz]

Possibly running on 3 cylinders from an open plug wire.
In dim light, or with the bonnet low, touch the plug ends of the wires in turn with the blade of a screwdriver.
Where there’s blue ‘corona’, not calling it sparking, there’s ignition voltage.
If not, travel up the wire to the dizzy to find the break.

[wheeler]

No plug leads or dizzy on the 16v's, They have a coil pack directly on top of the plugs.

[addo]

I'm interested to see what people suggest, as my car has similar issues at low idle. Quite vibratious!

[davidc]

Well thats 2 16vs in Australia with the same problem. Yes Adam hopefully in the Northern Hemisphere where cits aren't the oddities as they are here in Oz some one has had a similar experience....
David

[myglaren]

Don't know about the Citroen ones but those coil packs are a perennial problem with Renaults.

[addo]

I don't feel it's a misfire so much as a transfer of engine vibration. Mine is an auto, and the vibe is worse in D at a stop, than for N.

Sometime (ASAP) I want to weld another bung into the header downpipe. This will mainly be used for backpressure checking (but also can be for an additional wideband O2 meter in dyno operations). Reason I comment on this, is I'm wondering if it's an early sign of a slightly restricted paralytic converter.

Cheers, Adam.

[Downunder]

My Renault Laguna II 4 cyl 16 valve has the same problem. I think it may be coils. However as I have done only 52,000 km it seems a bit premature, especially as the car has the better Denso coils. I will take the car to a repair shop on the big island north of Tasmania, which has a computer to test the coils.

There is no vibration at 1000 rpm when I the car is first started. After about a minute when the engine warms up the vibration commences, at 800 rpm and even at 1000rpm. Disappears above that. Any inspiration?

[Sid_the_Squid]

Check for an air leak around the throttle body, or on one of the many breather hoses. I had terrible idle when I first got my 1.8 not so much lumpy but the revvs constantly wavered between 400~1000 like someone was piping the throttle, it used to die at junctions a lot too. Turned out to be numerous air leaks due to disconnected breather hoses letting air past the throttle body.
Coil packs are another option, so is the injector wiring, make sure theres no corrosion as the wires goto the injectors, had a nissan sunnzy ZX* once that used to drop one of the cylinders on idle, turned out to be a corroded electric contact on the injector.


*nothing like the regular sunnys, precursor to the Nissan sunny GTR