Technical Misfire with no fault code

[Chrisoleil]

Hello!

Just starting to get the cinq out for winter while the alfa hides.

It's running on 3 cylinders. It had all new sparks, leads, battery and coilpack. There is no EML lights and starts first turn of key and idles fine (not bouncy - just misfire)

Ran perfectly before changing brake lines which included removing the tank. The tank was off the car for 3+ months. I've also put fresh fuel in today but no change!

Could it be clogged filter? I will be doing a compression test but any other tests should I include?

Thanks!!

 

[Chrisoleil]

It's an 899 soleil before anyone asks

 

[Chrisoleil]

Also heats up fine, fan comes on and cools down perfectly.

Heaters blows red hot and freezing too.

Everything runs normal apart from being under powered and 3 cylinders.

 

[varesecrazy]

sorry daft question.., is it injection of carb..?, all fed from 1 point I assume,

try and pull plugs - see if only 1 is wet..,
or you're getting random spluttering,

Charlie

 

[The Black Box]

Charlie it's an spi injection same as a cinq sporting. It's a continuous ie on cylinder doesn't run at all. Need to see which cylinder is down then once found swap coils over to see if that moves which will rule out/in coils etc. I'd put it down to old fuel filter it looks almost original and tanks been disturbed so crud blocks somewhere?

 

[Metalguru3]

Hi Chrisoliel,

have you got 1 faulty spark plug - try the old set before doing anything too drastic.
Also - silly mistake I've made a few times - scraped up a sliver of electrode with the feeler guages when gapping plugs and this tiny anount of metal causes a misfire.

 

[Chrisoleil]

It drove fine for months with all the new bits Only change is that I've had the fuel tank off.

Even if it was spark plugs, surely it'd throw up a fault code? It's the lack of a fault code that's got me.

So plan: unplug a lead, start the car and check if that changes the anything? And get a new fuel filter on!

 

[fingers99]

I'd expect it to throw up a fault code eventually. But by then the cat will be fubar.

As it's SPI, fuelling issue would affect all cylinders.

From cold you can tell which cylinder is missing by putting a finger on each exhaust stub in turn. The missing one will be much slower to warm up than the others. (Safer way is to borrow an infra red thermometer).

Alternatively, pull the plug leads (insulated pliers recommended) one at a time. Missing cylinder will have no effect on engine speed.

Try swapping the plugs round, then the coils.

I'd expect the issue to be mechanical, otherwise, but easy enough to rule out the electrics.

 

[Chrisoleil]

I suspect it may be cylinder 4 as there's a white stain around on the lead near spark plug.

Have the old spark plugs and leads so will swap around and see tomorrow.

 

[Lecook]

May sound silly but does it pick up the 4th cylinder when its warm/upto temp?? Ive got a similar issue on my 899 where is wont run on all 4 until its up to temp.. although Im pretty sure thats down to hg or the massive bodge that was done on the lambda wiring

cheers
lee

 

[fingers99]

Lee's one is almost certainly HG.

 

[Chrisoleil]

Nope, let it get to temp and cool down several times with no change.

 

[Lecook]

Lee's one is almost certainly HG.

Its going in the bin so no real worries.. although theres a 30k mile gearbox thatll be going cheap

 

[fingers99]

A working 899 gearbox is a rare thing!

 

[Lecook]

30k miles.. in great working order..

 

[Chrisoleil]

Removed leads as above, appears to be cylinder 3. No change in idle with the lead removed. Had a look at spark and looked little darker than the rest, and I mean a tiny bit!

So removed all plugs, cleaned up them a little and put back in. Works fine now! Tiny splutter at low rpm, not enough to make me think the car will stall. Gave it an Italian tuneup and drove in 2nd gear for 3 miles to clear out the cobwebs!

Going to change the oil, filter and some new spark plugs then off to MOT.

 

[woj]

Just for the record, the older IAWs are not that brilliant with reporting missfires. Actually, I think the ECU will tell anything only once one of the coils is properly dead, but even then you cannot be sure...