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OBC detects misfire - what now though?

Wife's Amica Si engine management light came on last night and engine spluttered - no real power. Managed to get it home ok and I put an obc reader on it. It gave error code P0303 - "Misfire on cyc number 4"

So this morning I put in a new set of plugs gaped to 41" (Nowhere have I been able to find a workshop manual for this thing). I hope that gap is a good guess! I'm not even even which cyl 4 is (is it at the clutch end of the engine?).

Started up - and (yes) is still missing a beat. The leads are clean and dry (maybe look for sparks/lead-breakdown when it gets dark). Having said that, even when the leads are pushed onto the plugs they still wobble about - is difficult to say if they are really on.

At this point I'm stuck for ideas so would appreciate advice as to what to do next? If it's the ecu - that's a big job I guess?

ps If anyone has a w-manual for sale pls let me know.

Reply to
dave
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It's unlikely to be the ecu, try swapping the plug leads between cylinders & see if the fault follows them.

Reply to
Duncan Wood

ngk plugs should come ready gapped to 1mm for that car.

first check that there is actually a spark at that cylinder using a gap between lead and plug (there is a handy tool for this from gunsons) if no spark then find out where there is a spark up to, I guess this vehicle has a double coil pack in which case that will be the first suspect. if it has a distributor/single coil then look at distributor cap/rotor arm/plug lead. no 4 is the cylinder nearest to where the plug leads come from. if there is plenty of spark then check for disconnected injector (if it has one per cylinder) air leak on that cyl. then compressions

Reply to
Mrcheerful

tvm - will try these tomorrow. btw I can't actually see an ign coil anywhere - the dist. cover looks reachable though. Yes there is one injector per cylinder.

Reply to
dave

you could always try the old fashioned way to find the coil

follow the central lead from the distributor cap back to its source!!!

Reply to
TMC

if there are only 4 leads from the 'distributor' then it is a double coil pack if there are 5 then the one that doesn't go to a plug is going to the coil, but if that is the case (unlikely these days) then you know the coil is ok because the other cyls run.

First off establish if there is a spark at the problem cyl. then you can decide where to go next.

Reply to
Mrcheerful

Well somehow I seem to have fixed the problem (but don't know how)! Here's the ignition "pack"

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Here's a pic of the ign spark on cyl no 4
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I've seen better, but it seems to be working.

I disconnected all the injector connectors and measured the resistance of each: they all measure 14 ohms.

Measured (meter on DC range) the voltage on no 4 injector feed - is

12Volts exactly. (engine running on 3 cylinders). Also OI can hear the injectors clicking - used a stethoscope.

Used good quality contact cleaner on the injector plugs and sockets.

Put it all back together and the engine runs just fine. Trouble is I haven't actually found any fault! All I can thing of is that perhaps the connector wasn't making connection properly. Guess driving it and hope for the best is the only option now.

thanks all for the help.

Reply to
dave

I had that on a nova once, not running on one cyl. cleaned all the injector connectors and away it went, I guess they are very sensitive to a slightly bad connection. But I don't think it is a common fault.

Other question is: was it very damp under there at the time of the fault? sparks love tracking.

Reply to
Mrcheerful

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