Hi all, as title suggests, my panda 100hp has developed an intermittant cold start misfire. Have plugged a diagnostic machine into it which has given the code P0300 (multiple cylinder misfire - cylinders 3&4). Have had cars missfire in the past, one caused by a faulty coil pack, the other (fiat panda 1.2) caused by aged HT leads. Wondering if any of you folks have had something similar, if so, what was it?

When were the plugs last changed?

I noticed cold start rough running on my girlfriend's 100hp. It was almost up for needing new plugs. Changed them a couple of 1000 miles early and it solved the issue.

Could also be coilpacks, but if the plugs need doing it's worth starting there anyway.

The 100HP has a stick coil on each spark plug. If you suspect a problem swap the coils to different plugs and see if the fault moves.

When mine had a misfire, I was able to detect the problem using an IR thermometer on the exhaust manifold at cold start. This wont work with the engine hot. However, all four outlets should warm at the same rate. Barring anything mechanical, the one running cool has a spark plug, coil or other ignition problem.

The coil electrical connectors are difficult to remove. The cable trunking is bolted to the engine top. The yellow locking tab on each coil has to be pulled (IIRC) then the clip can be lifted and the plug pulled away from the coil. They are likely to be brittle so be careful.

It could be fuel pump. Turn on the ignition and wait a few seconds before turning the starter. It may well start ok or with less struggle. aAt the next cold start, turn the key straight to start. If it struggles to pick up you may have a weak fuel pump. Further investigation of fuel rail pressures is needed.

Thanks for the replies all, since posting, not had any more misfires. It was very windy and wet that night so a damp connector might have had something to do with it but so far as no more have appeared, i can only keep an eye on it. The sparks were changed around march 2019 i believe.