Alfa 147 twin spark rough idle

[Alfapride]

Hi all and merry Christmas! My 147 has started to have a real rough idle the engine shakes pretty bad and I can feel it through the cabin, once driving problem is gone and car feels great as ever. I've changed plugs, cleaned the throttle body and maf and done a ecu and throttle reset all to no avail...any ideas where I should hunt next???

[Citroënbender]

You could test the DC resistance of each coil pack output winding, you measure between the two spark plug connections (side and centre base) - this requires removal of the coil pack carrier assembly.  From memory 9K Ohms is the ideal figure. 

[bazzbazz]

Check engine mounts

[Alfapride]

The mounts look ok I'll try testing coils later I initially ruled them ou as the car drives fine it's just idle where the problem arises I should say cold start is ok takes about two minutes for the problem to present itself. Driving and coming to a stop the idle drops almost stalls but brings itself back in time...

[Alfapride]

Quick update noticed it's actually misfiring could tell by listening to the exhaust the fumes are awful too smells almost farty...disconnected the maf no difference in symptoms I'll let the cat cool down and look further tomorrow

[bonno]

Hi Alfapride
Did the rough idling start immediately/soon after filling up at the petrol station, ie; bad batch of fuel.

[Alfapride]

Hi there no tank is three quarters full filled up a week ago problem started two days ago and getting worse

[Colin Edwards]

Is the car using coolant?  An iffy head gasket can allow coolant to condense on to a spark plug overnight. 

First time cold engine starts, plug misfires causing engine to run rough until condensed coolant on plug evaporates.

[Alfapride]

G'day Colin coolant level is steady and clean so I'm praying head gasket is still good

[bazzbazz]

To be honest, you could very well be chasing your tail without first getting it hooked up to a Alfa Romeo Diagnostic suite by someone who knows what they are doing, doing so could reveal the fault instantly.

It could reveal blocked Cats, faulty coils, faulty Cam Angle Sensor, ect ect.

At the very least look for a split, bad sealing of the air induction piping from the MAF all the way to the throttle body. A split in the Concertina Piping is possible.

Last but not least, have you noticed any decrease in the Braking or Vacuum Brake Boost system? (I do ask for VERY good reason)

Baz

[Alfapride]

G'day baz I agree diagnostics would make it easier but it's a horrible time of year for this to happen most of the mechanics here are closed for two weeks if it's a small problem that I can fix myself prior that would be ideal ...braking is fine brake pedal feel is normal unchanged. I'm going to test the coil packs tomorrow with my multimeter

[Alfapride]

I tried to test the coils today I got 20k in all four? Wondering if I tested correctly I used a probe in each spark plug terminal two per coil pack? I measured across the two top terminals all the readings there were the same approx 10 ohms all the coil packs look to be original

[bazzbazz]

Your readings are a little off, but not much, more likely resistance in your connectors/setting on the meter would account for this.

The telling point here is that all 4 coil packs gave the same readings, and the likelihood of all four failing at once is unlikely, so you can assume that the coils have passed your resistance check. This does not mean that there is no fault in any of them.

Have you checked the air intake path for loose clamps ot splits as I suggested?

[Alfapride]

Your readings are a little off, but not much, more likely resistance in your connectors/setting on the meter would account for this.

The telling point here is that all 4 coil packs gave the same readings, and the likelihood of all four failing at once is unlikely, so you can assume that the coils have passed your resistance check. This does not mean that there is no fault in any of them.

Have you checked the air intake path for loose clamps ot splits as I suggested?

Hi baz yes I checked the clamps and air hoses to the maf I can't find any holes or leaks looked good...put some injector cleaner in this morning and topped up the fuel tank but no change was worth a shot haha

[Alfapride]

Quick update it's a lot cooler today in Melbourne car drove well for 15 minutes then the problem came back...convinced it's temperature related I'm going to look at more hoses tomorrow and might swap over a few sensors to test