Hey folks, hope you are all well. These are more of a concern than real issues atm but Id like a bit of clarification anyway. Picked my car up from JMH today after having yet more £££ given to it for new rear wheel bearings (its great now some may remember I posted about this before). Id got about 4miles down the road and the 1-4 CEL light came on, lit for about 2-3 secs then went off again...didnt see it again during the remaining 20mile journey home and havent had this before....should I be concerned or not? Secondly, during the past 4 weeks my idle has got increasingly worse, it missfires intermitently and also missfires quite a lot when im pulling off nice and steady, if I give it some beans its fine....also if Im driving in say 6th gear @ 2000rpm, and apply throttle, it starts to missfire then too. Above 2500rpm and WOT its fine....Im assuming this is either going to be plugs or leads? or could it be something more sinister and that flash of CEL is related to the missfire even? Cheers Dan
mine does/did similar, but on the 5-8. I've got a long thread on here that goes over my trials and tribulations, but the problem is still not completely cured. I think mine is a wiring issue that I am going to tackle once life slows down enough. Not much help, but if you get it resolved, post up...
You need to read the ECU error codes. If you have a 2.7 motronic 355 (early models) your MAF's can be heading south or your O2 sensors are getting old. The MAF has a screw that sets the CO (fuel to air mixture) when the O2 sensors go open loop. O2 sensors go off line causing an open loop when they are too cold (their internal resistor will force a 0 reading until they come to temperature) or when they are at the end of their life, where their values go too far off the scales, and the ECU starts ignoring them. At this point, the ECU goes open loop and uses the CO screw on the MAF to guess the fueling based on a limp home map. If the MAF screw is set to rich (which it is by default to prevent other problems) then you can get over rich and misfire as you throttle up. When you are at a higher RPM everything is fine as the air fuel ratio is closer to what an engine under power needs. A way to test this PRIOR to changing O2 sensor, is to warm the car up good and well, then disconnect the O2 sensor (pre-cat) on the offending bank, put an ohm meter on the MAF pins 1 and 6 (motronic 2.7 only) and read the original setting. Then increase the resistance to around 500 ohm, and if the misfiring improves your O2 sensor needs replacing. When you replace the O2 sensor put the MAF back to the original setting. O2 Sensors do not have to come from Ferrari. You can buy standard universal 4 wire BOSCH sensors with thimble zirconia tips for a mere fraction of the SAME BOSCH sensor but in a yellow box from Ferrari. You can then buy some plugs and wire them up. Also change the O2 sensors on both banks when you do! Marco
Thanks for that!! That makes a lot of sense, and also tallys with a couple of days ago.. A friend of mine was driving behind on the way to drop the car off for some work, I opened it up and he said he could smell fuel as if it was running a bit rich. Cant hurt to change the plugs and leads also, running rich is gunna foul the plugs up anyway. Thanks again for the info.
plugs and leads will set ou back 5-700 GBP. First fix the cause of the rich running. Then take the plugs out, get a brass brush and give them a quick buff. The engine will sort them out within a hundred miles of running at the right mix. The leads, well, if it all runs smoothly once you've got it set up right, then no need to change them. What you can do is get an ohm meter (multimeter) and measure the resistance and continuity across them. The first and third, second and fourth cylinders in each bank fire the sparks at the same time (one will do in the compression cycle and one will be a wasted spark in the exhaust cycle) as the coils are twin spools driving 4 plugs. The "best" setup is that the plugs in matching cylinders should have the exact same gap, and the wires (leads) should have the same resistance. Electricity always takes the shortest route, so you want to make sure the potential energy gap at the spark plug gap is the same across both plugs so that the spark heat is the same too... M
Marco's got it right above, but I'd handle it more lazily become I'm a Stooge. First, pull the computer codes. Can't hurt to know what your computer(s) see. Second, I'd reset the computer(s) so as to start from scratch. Very simple to do if you are running M2.7, just turn off the battery when the car is cold, turn it back on, start the car, and let it idle without touching throttle or anything electrical for 10 minutes. Done. The above codes and ECU reset will give you a baseline that's useful for diagnostics (and that often clears minor problems). Now make sure that your air filter is clean and that you hear no obvious air intake or vacuum leaks with engine idling. Then I'd pull my MAFS and clean them with CRC MAF cleaner internally, and coat their external electrical connectors under the black plugs with Stabilant 22a. Again, cheap, quick, easy to do and fixes many problems. If the problem still persists at this point then I'd disconnect the front O2 sensors. This *will* throw ECU error codes, but driving at low speeds with the O2's disconnected should tell you if your O2's are the problem...if the problem disappears with them disconnected! If so, then simply replace them with cheap generic O2 sensors (Bosch O2 sensors aren't great). If the problem *still* persists, then I'd pull the spark plugs after a hard drive up a long hill and read them. See my thread in the blue link in my signature below. That will isolate the problem area for a more serious problem-solving attack later.
CRC cleaner is here: http://www.midwayautosupply.com/showproduct.aspx?productid=3640&affiliateid=10050 Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Most auto parts stores carry it. You can find it on the Internet. It's about $12.00 USD. If you have trouble in the UK, I KNOW FabSpeed sells it. To clean the MAS, just disassemble it from the air intake and spray the hot film sensor from both sides. Although it's over-kill I used the whole spray can. No need to absorb the excess, as it dries without any residue. Make sure you clean the electrical contact and (if possible) use Stabilant 22 contact enhancer. FabSpeed Link: http://www.fabspeed.com/ferrari_355.html
Link: http://www.ricambiamerica.com/advanced_search_result.php?keywords=Stabilant&x=5&y=7 Also, http://www.stabilant.com/bccomp.htm. But buy it from Daniel at Ricambi.
