Dear fellow F355 enthusiasts. I have read many extremely knowledgeable posts by many of you and would very much appreciate your thoughts on my problem that has been dragging on for far too long. Intermittently, but seems to get worse, my 1995 Motec 2.7 F355 Berlinetta, starts to misfire badly and loose a lot of power. Seems to be mostly when warmed up. (just warm, not like potential overheating after hard driving) Possibly that one of the banks basically stop working, temp seem different on the cats after shut down. But not at all sure. There are no lights lit on the dash though. Neither amber or red. Only indication is the powerloss and very different sound that any car person can hear. Sometimes even some light exhaust bangs. (thinking maybe from unburnt-fuel entering the exhaust. It has been like this for a while and Ferrari Barcelona has worked on it several times and keeps coming back after a few hours driving or just 5 mins... Mechanic even connected computer once when it was misfiring, so disappointed they haven't been able to find source of problem. Runs like an absolute dream initially, then after random amount of time "switch" over to running rough. Usually start up and run perfect again after having shut down for a few mins. So got to be something electrical, not mechanical. Car is generally very well serviced, but unfortunately haven't been driven regularly enough for a few years. Could be part of the problem. I replaced one crank position sensor (unfortunately could not get to the other one. Looked good though and the one replaced seemed fresh. cleaned and exercised connectors. I am on my 4th set of cats now as the have been burnt out. Possibly due unburnt fuel in exhaust. Now refurbished originals. Running tubi headers and Capristo 3/1 exhaust. Worked perfectly with these items first few years though, even long cross-europe road trips. One of the cooling fans (right side) would not come on recently and engine coolant temp approaching overtemp. (caught in time) After trouble shooting worked again, no complete evidence but my best guess is that one of the connectors in the engine bay did not have good contact. Cleaned and exercised the ones I could access and now works well. Will tow to Ferrari shop once again soon. Want give comprehensive list, with your help, of things to check/replace as they have been unable to successfully troubleshoot several times before. Sorry for long post. Really need you knowledge and experience partners!! Sincerely /Rickard
Back to first principles. Do you have spark? It is not normal to routinely burn through cats. These cars are known to go through HT leads and coil packs reasonably quickly, which could lead to dumping unburnt fuel through the exhaust, and bore washing. Also, does your slow down light come on then extinguish at startup? Does unplugging the cat ECUs solve the problem? Finally, find another mechanic. You shouldn't have to furnish Ferrari with info on how to fix your car.
I've had similar problems and while I don't like to just replace part sometimes with intermittent problems sometimes it's easiest to spend a little money. Replacing the coils and the power modules is a cheap DIY. Fixed my problem. Power modules = Bosch 0227 100 200, also Porsche part Porsche part 99360270601 (94-95 911) . $48 on amazon Coils are : BOSCH 221503407 or BOSCH 0 221 503 407 $35 on amazon Or cross reference. Replace Part Numbers ALFA ROMEO 60558152 BERU ZS234 BERU 40100234 BERU 0 040 100 234 DMB300 LUCAS CAV LAND ROVER ERR6045 LAND ROVER ERR6566 LAND ROVER ERR604 FIAT 76487970 FIAT 7648797 FIAT 60809606 FIAT 60558152 HELLA 5DA749475-041 KIA 0K0-11-18-100 LUCAS CAV DMB300 PROTON PW811201 VAG 489051051 VAG 048 905 105 1 ZS234 BERU
not sure if there is spark when misfiring, as it is still running then. Later will start up again perfectly, for a little while. Yes, all lights come on and then off during power on self test. Thanks for the idea of coilpacks and HT leads, could be. Where do I access cat ECUs? /Rickard
What about a smoke test? did you.consider an air leak in the intake manifolds? Too much air not balanced, engine runs too lean randomly misfiring, temperature skyrockets and kills the cats ....
Sorry for my inexperience but how do I make a smoke test? Also the change from good to bad is instantaneous. Almost like you can hear a click from running like the responsive nearly racing car we all love, to running like garbage and a lot less responsive to throttle input.
Could be the car going from open loop to closed loop mode if it's literally a switch. Duff lambda sensors causing overfuelling perhaps.
I imagine if it’s a leak somewhere should be more slow transition. It feels like some electric module all of a suddenly goes fully off center or even shuts off.
Thanks. That sounds quite plausible. Can I test lamda sensors somehow? Also surprised Ferrari didn’t think of that or just replace them at their several troubleshooting. Difficult to replace yourself?
Yes, simple to replace, but I would just get the car to a competent mechanic rather than throw parts at it. It'll cost more than simply throwing on coil packs and lambda sensors but cheaper than new cats.
Yeah. That’s what it seems like. Just switch over, one instant to the next. No one had this before? Not gradual in any way. From awesome to garbage.
Only positives is seem to get more frequent than random and therefore easier to troubleshoot if whatever module or sensor fails properly.
