Synergie 2.0 petrol - lumpy idle?

panther12 · Post by **panther12** » 03 Sep 2005, 01:46

1996 Citroen Synergie 2.0 (Petrol)
My Brother has asked me to look at his Synergy. He says it's idling very lumpy and sometimes cuts out at junctions. I took it for a drive and although I’ve never driven a Synergie before it feels very gutless lacking power and needing a lot of full throttle use. It sounds to me like it has an air / vacuum leak but all pipes and connections appear ok. When you take your foot off the throttle the revs will sometimes drop to almost stall before levelling out at a lumpy 950rpm – but sometimes does stall when approaching junctions.
Any pointers welcome.

AndersDK · Post by **AndersDK** » 03 Sep 2005, 03:40

Do a full service if not done lately.
It's <i>VERY</i> often one of the common service points that needs attention. Any history on repairs done lately ? - as this is often a good start on fault tracing.
Fuel filter
Air filter
Spark plugs
Ignition leads
Oil filter
Engine oil

panther12 · Post by **panther12** » 04 Sep 2005, 04:10

Thanks for the reply. Out of that list I think there is just the fuel filter that hasn't been changed but it has a gas LPG system fitted and still runs lumpy either on gas or petrol, so I think that would rule out any fuel filter or injector problems as the gas would bypass that. It has high mileage 220,000 and has had a top end engine rebuild by a Citroen specialist (pistons rings, cylinder head, valves ect).
Also had a new MAP sensor but made no difference. I was thinking if it could be the Idle air control valve. With the IAC disconnected the revs increased to about 1400rpm but still ran very lumpy - although the revs didn't drop below 1400 when you blip the throttle. If the IAC valve is sticking would that give the symptoms of a vacuum leak and make it run lumpy?
What also concerned me is that I noticed that the Check Engine (MIL) light on the dash does not illuminate when you turn on the ignition so I suspect that the bulb may have been removed. I have a copy of Autodata CD and that gives the procedure to access any fault codes using the homemade LED & switch method connected to pins C2 & C3 on the 30 pin plug under the dash. It didn't work so I think these need to be connected to a dedicated fault code reader. I will try giving the IAC a good clean with carb cleaner and see what that does.

AndersDK · Post by **AndersDK** » 04 Sep 2005, 04:53

Please give all info on model/modifications in your first question !
- otherwise the chance on any sensible answer is about 0% [8]
The LPG info is just about the crucial point. Any LPG installation will modify the fuel injection system to such an extent it does not function anymore [8)]
If this problem is to be corrected - you must firstly insure the engine is able to run clean and well on petrol controlled by the standard ECU setup.
There are in fact LPG systems around containing the extra gear needed to be controlled by the existing ECU. I doubt this is installed as these systems are like diamond rings on a full hand.
This is also indicated by the missing ECU fault lamp [:0]
- it's been cut mate [8)]
My bet is you can go ahead and replace just about any bit fitted to the existing engine control system - and it wont help you an ants hair.
Because the LPG system runs completely out of control of the existing engine managing system (except ignition).
So you're left with the LPG gas injection nozzle and regulator.
If I were you - I'd leave this for a professional. Any gas outside the intake in engine bay + a spark - and you're out of business as the friendly car fiddler [V]

panther12 · Post by **panther12** » 04 Sep 2005, 23:25

Thanks for that. Sorry I missed off the LPG info, I now realise that was important. I told the Brother about the LPG effects on the ecu / management system and he assures me it has been running fine for months after the conversion. I had another look at it today and removed the IAC valve to give it a good clean (it was very mucky) and noticed that the plunger does not move. If I hold the IAC and turn on the ignition I can feel 3 pulses but the plunger does not move. I wasn't sure if this was meant to move on ignition or only when the vehicle is moving? I measured the resistance between the 2 end pins and the 2 middle pins of the IACV and they were within spec (53 ohms) but even connecting it to a 9v battery the stepper motor did not move. I cleaned all the gunk off and replaced it and the car started but this time would not even idle at all. After a while it started to idle just as it did before very lumpy. Do you think this sounds like a faulty IAC valve?

Mosser · Post by **Mosser** » 05 Sep 2005, 01:07

If its a true stepper motor, then a dc current wont make it move at all, they run on a sort of three phase control signal that controls the position and speed, and the three pulses you feel when you turn the ignition will be the stepper motor making sure its back at the start point so you shouldnt see it move normally, can you try pulling the plunger out ?, it should move back to the home position when powered then, but if its a geared stepper then moving it might well break the gears as they are usually plastic

panther12 · Post by **panther12** » 05 Sep 2005, 02:30

Hi mosser. I did try applying hand pressure to the plunger in both directions but it is solid and I was worried I'd break it with too much force. With the ignition on you feel 3 pulses, Nothing happens when you turn ignition off but turn it on again and there is just one pulse, and then 3 again on the next turn (but no actual movement). The last IAC I cleaned was on a Daewoo and looks similar to this one but on that the plunger moved forward on ignition and switch off it moved a little bit more forward before closing - but I suppose different vehicles operate in different ways. Apart from the usual carbon build up on the tip there was also a lot of thick gunky oily deposits on the plunger which I cleaned off with injection cleaner.