Ignition Troubles...please help.

[sidub]

My series 3 (\'94) twin turbo has an ignition problem and i cant work out what\'s wrong.
 
The engine shakes a little on idle and throughout the rev range and at 2000-2500rpm it shakes quite alot.
The issue is with ONE of the outputs from the leading coil pack. When i use a timing gun, one of the leading plugs is sparking at the correct time but the other leading plug jolts about quite a bit. When i swap the leads over between the leading plugs, the problem stays with the lead and not the plug.
 
it is not:
crankshaft position sensor
spark plugs/plug earth
HT leads
coil pack (checked, then replaced anyway just incase it was this as i was pretty sure it was.)
 
As the lead coil provides spark to both plugs simultaneously, i dont quite understand how one output is fine but one fluctuates/misses occasionally.
 
Does anyone have any ideas? or has anyone experienced this before?
My next step is to check all wires and connections associated.
 
thanks,
Simon

[nikp]

ECU possibly? The ECU controls the timing for the leading and trailing plugs, so if the coil pack is ok, then surely its the ECU?

[Bobbit]

If it stays with the lead i\'d say it was the lead, but your posted it not the lead. So i\'m stumped.
Have you changed spark plugs and leads?

[sidub]

ECU, plugs and leads have all been replaced.
its a tough one, isnt it!

[nikp]

Well, i\'m all out of ideas then!

[RemarkLima]

Only thing left surely is the wiring... Don\'t know how hard it would be just to run some seperate wires to the coil pack... Gotta be easier than putting in a new engine loom.

[Bobbit]

Have you tried hitting it with a hammer? Worked on my starter motor, lol. Wiring looks like the only culprit left then bud.

[leon]

I have a spare ecu if you want to borrow it - I live in cleckheaton just down the road from ya, Have you thought about checking over the grounds? or even doing a check for error codes from the ECU?:Thumbs-up

[logicalChimp]

Hmmm

The following is armchair speculation, from one who has never played around in this area

Have you checked the lead connectors, on the coil side?  If both leads come from the same coil, and one is playing up, then it would logically be either the lead, or a dodgy contact.  You say you\'ve replaced the leads, so that only really leaves a dodgy contact...

[rustyrex]

more armchair speculation.....
would the ignighter be the problem?(passenger side by the abs gubbins)i,m just a numpty and dont realy know if the ignighter is conected to the coils all i know is i had to unplug it when i flooded once (pressumibly to stop leads sparking when turning over to get petrol out the engine)
one more thing to rule out?
good luck tho

[sidub]

Haven\'t had much time over the last few weeks to work on the car until this week...
It has now recently had:
New HT leads
New ECU
New spark plugs
New Igniter
New MAP sensor

Crankshaft position sensor is fine
I have checked most of the important wires and connections with no problems so far.

The problem still exists.
Im now thinking it could be a dodgy knock sensor....
When i get the timing gun on it now, both leading plugs occasionally miss a spark. Also when using the timing gun the timing is occasionally erratic (leading) and from ALL coils it is as though the car is constantly advancing/retarding the timing (upto +/- 30 degrees) when progressing through the rev range. At higher engine speeds (+5000rpm) the problem  disappears.

Can anybody tell me exactly what their ignition timing does on their RX7 when using a timing gun? Does your car constantly advance/retard the timing throughout the rev range?

Ta
simon