Good evening all, We have a recurring issue on a Fiat 500 1400 petrol where we have had the vehicle first presented with lumpy running and fault codes P0300 random multiple misfire and P0303 Cylinder temperature too high and P0304 Cylinder temperature too high.
We carried out a relative compression check with Pico showing all with 98% and followed up with gauge check with all cyls showing 180-185 Psi. We scoped the coils and found drop outs across the board and cyl 3 being worse we swopped plugs which moved the worst drop out to cyl 2. We recommended coils and plugs after we found some cheap range coils from Euro fitted. The customer paid to upgrade from cheap to Marelli coils and new NGK plugs. We smoke tested and found breather pipe to intake tube split so replaced that pipe. After fitment the car ran smooth but noticed the rear O2 sensor long term trim is showing at 99.2% but sensor was working with short term trim working well. All adaptations were reset and car has been on road trouble free for 4 days but went to limp mode today and customer reported lumpy idle after cold start yesterday morning then ran fine. It was recovered in in limp today.. We have fault code P0300 and P0304 returned with slight lumpy running. Checked fuel pressure at 3.9 bar with data showing 3-3.5 required, this leaks off with engine off but holds good when running. There is no cylinder wash but cylinder 4 piston crown is oily compared to rest but plug electrode is clean. History shows a recent cambelt but no other work. Had been to dealer before us who advised all injectors be replaced. I am waiting on our injector tester to be returned from repair before I can check injector balance but bank 1 fuel trims are normal. Has anyone had the fault codes for cyl temps too high on one of these? . The engine runs very hot under bonnet temperature with coils very hot but coolant temp is correct. We don't see many Fiat 500s but the under bonnet temps concern me. We are going to pump up coolant tester tonight and use video scope in morning to see if any minimal water entering cylinders as head gasket check is ok. Anyone been here with a 500

Does the 1.4 require a phonic wheel relearn after a cambelt change like the smaller fiat engines? This causes misfire issues.

Matt

I haven't had those fault codes, but have had random misfire (P0300) on the 1.2 due to incorrect valve clearances.
We don't get the 1.4 in the Ford Ka though, only 1.2/1.3.

Tony

Declan,
Where did you get the description for your fault codes, as i understand it P0303 and P0304 are misfire codes for cylinders 3 & 4 !

Regards
Dave

Hi Thanks for the replies, the fault code terminology is off the bosch but yes agree they are misfire codes. We have looked further on Saturday and found oil entering no 4 cylinder bore, it also looks like its got lots of history as gearbox been replaced, and has had sump off whether for a oil leak or whatever but they cut the cat to lower the sump then welded up again after repairs and ECU wiring has been pulled about a bit so looking like it has had some issues along the way
It turns out customer has only had car for 3 weeks
and the garage who sold it are coming to get it. so we might not see the fix as its very intermittent