I have had this car for 6 years. I am really happy with it. Over the last 40,000 miles it has developed an ignition problem that the main dealer can't solve. During the summer only, when the weather is warm, if the car gets warm in traffic or is left to stand with the engine off after it has been running for some time, it misfires. The way to solve this is to leave the bonnet open (hood if you are in USA) for 2 - 3 minutes. It then totally recovers and all runs normally. If the bonnet is not opened, it will need 30-40 minutes before it will start normally. The fault code says that there is injector failure for cylinder 4. Swapping injector 4 for injector 5 makes no difference - it still registers injector failure cylinder 4. There is really nothing to suggest a problem with the injectors. All the following have been done with no effect; All 5 coils have been renewed. All plugs replaced. Air mass meter replaced. New air filter. When not misfiring the engine runs perfectly. No loss of power or fuel economy. Any ideas please?

 

Could, be the fuel rail ....there is also a fuel pressure regulator sensor I would say that you may have some exposed wires that half to due with ignition engine wires.. I recovered all of mine just to be safe but by this happening when its hot is pointing me in that direction...Heat slows down current ...pull the wires off the engine rap them with tape and don't let them touch anything hot . Rerap electrical tape over any thing that looks suspect....my old wire covering crumbled as soon as I touched them.

 

Thanks, I'll have a look

 

OK so when I replaced my spark plugs and recovered my coil wires I forgot to tighten down one of the six black coil ground wires and after I connected all the pipes and Volvo plastic covers up 30mins .I started her up and had a miss fire after 3 mins of idle....wow what a Scarry sound that was . I hooked up the canner is said missfire ignittion ground wire coil 4.....so what I'm saying is that the bolt was tight but not tight enough and anything thing in my opioion that is in that area that is a tinny bit off , expossed coil wires,coil grounds, corrision and heat can be a big to small issue. Hope this gives you a bit of inside experience bud

Cheers

 

OK so I have done all this problem remains the same. I have also cleaned the earth connection between coils 4 and 5. Warm weather in UK means that problem now coming more often. If I stop and open bonnet for 3 minutes problem clears. Interestingly, this happens if I stop in the shade. If I stop in the sun and open the bonnet with the sun shining directly on the engine, the problem does not clear until I move to a place where the engine can be shaded. Further ideas?