[urq] random missfire , non ur-q

[Patrick Carlier]

I need some brainstorming guy's . 

My wifes's car , 4 cil 2Ltr citroen . 
Symptoms : 

Hesitates and stumbles and bucks at low revs . 
Idle's pretty rough altough within reason . Engine's got 236.000 Km on the odo . 
Starts without problems , hot or cold . 
Once above roughly 2000 RPM , it behaves quite normally with decent power 
and normal fuel consumption .
I 'de say that the problems is worse with a hot engine but that could be subjective . 
Offcourse the CEL is alway's on , and when the problem occurs it starts flashing . 

Tried : 
New spark plugs  : noticeable improvement , but not cured . 
Fixed a broken crank case breather hose :  noticeable improvement but not cured . 
Full service , oil air filter etc : no improvement 
Ultrasonicly cleaned the injectors : no difference . 
Compression test : OK . 
New oxygen sensor : no improvement . 

So a bit unsure on how to proceed , I got  me an obd2 reader wich indicates random missfire  . 
A quick search on the net : change the coil pack . 

What do you think . 
Can it be that a faulty coil pack only causes problems at low rev's . 
Last week we went on a trip , 2 hour drive on the highway , at  high speed 
all the time .4 Adults , 3 kids so it was loaded . 
Car behaved perfectly until we arrived at our destination , with lots of city traffic .

 
I'm a bit reluctant to just start swapping parts without knowing for sure they're defective .
Especially with an expensive coil pack , wich appears to be working fine at higher rev's . . 
 
Pat