NC 3.75 - Misfire on idle after standing for a while

Technical Area Engine, Transmission, Exhaust etc
1

I have a 2013 NC 3.75 based in Stoke on Trent, it’s been in the garage for a number of months, and came to move it last week and it was idling rough.

I plugged in ODB reader, and got P0300 Random misfire. Looking further into the ODB info, the misfires seem to be on cylinder 1 and 2. 1 has lots more misfires than 2.

Ive cleaned the MAF, Cleaned the throttle body, replaced the plugs, and replaced the 4 coil packs, and no difference.

Ive tried disconnecting battery, and when reconnecting, getting the revs upto 3k for 3-5 mins, and while the revs drop back down after 3 mins as expected (assume means that the relearn is complete) the misfire is still there.

When its warm is difficult top start too, take a while to fire.

Any ideas where I can go next? Injectors sticking, compression?

Thanks

2

Might be worth sticking a pot of Redex in and taking her for a spirited drive.

3

Poor running and random misfires after standing for a long time could just be stale fuel. Over the years I’ve had many cars that have sat for a long time between uses but never have any issues. Before using it again I’ll fill a jerry can of fresh fuel and add a bottle of liquimoly octane booster then tip it in. A trip to a petrol garage and top up to full with super unleaded should hopefully bring the fuel up to sufficient quality to run well.

4 Likes
4

Great advice from @Dean_S550 - just filled up with 99 RON - went for a blast, and its seems spot on!

ODB is registering no more misfires, and pulls well again.

Thanks for the tip on that :slight_smile:

3 Likes
5

Really glad it helped :+1:

1 Like
6

The tried and tested “Italian Tune-Up” technique!