F355 unsolvable issue - please help! | FerrariChat

F355 unsolvable issue - please help!

Discussion in '348/355' started by nicklondon, Jun 21, 2019.

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  1. nicklondon

    nicklondon Rookie

    May 21, 2013
    19
    London
    Dear All,

    My F355 (2.7) has a seriously frustrating issue that no one can get to the bottom of.. I have spent huge amounts of money and given it respected engineers to try and resolve and they're stumped.

    Basically when she sits at idle (particularly when running hot) there is a very annoying stutter. I have attached a link for a video which will be better than me explaining. The slow down light illuminates and when you give some revs it disappears. The ECU's have been checked, the wiring looms have been out and checked, the alternator, the alarm removed.. literally everything.

    Any help would be greatly appreciated as I genuinely love the car but just can't get to the bottom of it.

    Many thanks in advance.

     
  2. F355Bob

    F355Bob Formula 3

    Have you checked cat ecu and thermocouples ,TPS? What codes does the ECU sending out?
     
    ernie and INTMD8 like this.
  3. Pangea

    Pangea Formula Junior

    Mar 27, 2011
    442
    UK
    Full Name:
    Nick
    My 348 did exactly this at idle. Same light behaviour. Try disconnecting the LH cat ECU if not already done. Not the main ECUs. It was the problem for me.. Hard to see its anything else. Also, as said above, what codes are stored? But then again ,literally everything has been checked you say.
     
    ernie likes this.
  4. ernie

    ernie Two Time F1 World Champ
    Lifetime Rossa Owner

    Nov 19, 2001
    22,574
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    The Bad Guy
    In addition to what has been said,

    It may also be time for a fresh set of EPROMs in each of the Motronic ECUs, and check to make sure that the female pins in the T55 connectors are in good shape (not gapped), clean, and making proper contact.

    Here is how I replaced the EPROMs/chips in my 348 ECUs.
    https://www.ferrarichat.com/forum/threads/348-ecu-removal-chip-removal.351819/

    and,

    How I repined my T55 connectors.
    https://www.ferrarichat.com/forum/threads/348-motronic-2-7-connector-harness-repin.444155/
     
    GSF355 likes this.
  5. nicklondon

    nicklondon Rookie

    May 21, 2013
    19
    London
    Dear all - thank you for your responses so far. Cat ECU's have been looked at, Main ECU's have been swapped with a donor car as well to no success. It's a very strange one. I think myself that it's exhaust related, I forgot to mention that it started doing it after I removed a noisy sports exhaust that was on the car when I bought it and put a factory system on. Thermocouples have been checked as well. I'll try and get the codes the ECU is throwing out
     
  6. fboutlaw

    fboutlaw Karting

    Dec 3, 2014
    237
    Woodside, CA
    Looks like idle hunting. Could be a very wide range of things.

    I agree with Ernie that if you swap all the pins, that at least takes old connectors (which can be an issue) out of the equation. Available: http://****************.com/sri-gold-connector-kit/

    Air, Fuel, Spark:
    Air: Could be bad pins at your MAF. A bad MAF.
    Fuel: Clogged injectors (or 1 bad injector that gets masked when you're revving the engine). Bad Pins to injectors.
    Spark: Bad pins, weak spark at idle, bad battery, bad alternator

    Pull codes, if you can, check the running voltage of the car and if it dips at idle when the alternator slows down. In all cases though, bad pins can be a culprit. I did the SRI kit myself about 6 months ago, and without any other changes, all my intermittent issues went away.

    Good luck!
     
    Qavion likes this.
  7. johnk...

    johnk... F1 World Champ
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    Jun 11, 2004
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    John Kreskovsky
    #7 johnk..., Jun 21, 2019
    Last edited: Jun 21, 2019
    If it started after changing the muffle, have you tried changing it back?

    You say literally everything. Plugs, coils, power modules, ..... what exactly has been done? Who is working on the car? Have they connected an SD1 or 2 to the system?
     
  8. drbob101

    drbob101 F1 Rookie
    Owner

    Nov 26, 2012
    3,814
    Tinton Falls, NJ
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    Bob Ferraris
    If you are correlating the situation with the slow down light it could be as simple as an intermittent short in the sdecu/tc system that is momentarily shutting down a bank and then resolving itself.

    I just posted a video in another thread of an intermittent TC short spiking voltages and creating issues. The TC bench tested just fine but when installed was faulty.

    The only way to know this is to tap the sdecu outputs (you have 2) and monitor the voltages and see if they’re spiking like this vid and then troubleshoot/ replace.

    Without tapping and checking voltages you can just replace parts. New sdecu (green potted) x 2 , new thermocouples x 2.

    Not sure this is your issue but it could be and I had intermittent bank shutdown as a result of an intermittent faulty TC that bench tested fine.

     
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  9. Mats Andersen

    Mats Andersen Karting

    Sep 28, 2017
    144
    Norway
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    Mats Andersen
    As suggested. Did you try putting back noisy system? If it happened after you replaced the exhaust it 100 percent is related to that. Or somerhing was damaged during exhaust replacement.

    M
     
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  10. SoCal1

    SoCal1 F1 Veteran
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    Jun 14, 2011
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    SoCal LA/OC/New Mexico
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    Tim Dee
    99.9% of the time if you have an issue its what you just did, if not

    Check your idle valve they do that when bad or a bad connection or vacuum leak, think you may have 2 on 2.7
     
  11. johnk...

    johnk... F1 World Champ
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    Jun 11, 2004
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    Unless the issue with your wife. In that case you have no idea what you did, when you did it, or even if you did it. :(
     
  12. Ferrarium

    Ferrarium F1 Veteran
    Rossa Subscribed

    Jul 28, 2018
    5,624
    Central NJ
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    Eric
    You can clean IAC valves with maf cleaner you can find youtube videos also the maf itself, give it a spray. One of my IAC hose was loose from service, I did not have a problem but check all that when you clean them. On the 348 we reset the maf voltage after cleaning it. Probably not the maf but can't hurt. I read some cars having this exact issue out here where they replaced the ignition modules to fix it. I replaced mine preventatively after I read that. Cost about $60 a piece using Bosch part #.

    Good luck!

    Sent from my LM-Q710(FGN) using FerrariChat.com mobile app
     
  13. Qavion

    Qavion F1 World Champ
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    Feb 20, 2015
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    Have the technicians been able to reproduce those symptoms in the shop and do you know what they have specifically done to address the Slow Down light issue?

    Did the sport cats come with extenders (for the O2 sensors)? If they were refitted, maybe they shouldn't have been (and just the O2 sensors fitted).
     
  14. drbob101

    drbob101 F1 Rookie
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    Nov 26, 2012
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    Again, if you correlate the issue with the sdl then you should be focusing on the things that are triggering a sdl and bank shutdown.

    Eliminate the sdl and if the problem persists then on to the next possibility. Unless you have a true cat hot issue the sdl is an easy fix
     
    Pangea likes this.
  15. johnk...

    johnk... F1 World Champ
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    Jun 11, 2004
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    I bet the SDL is a symptom, not a cause. Also, MAFs on the 355, 2.7 are not adjustable.

    How about a bad connection to or a failing crank sensor for bank 2. At low RPM, like idle, the output is too low and the banks 2 ECU thinks the engine isn't running so bank 2 shuts down and the bank 2 SDL comes on. When the throttle is opened up the rpm goes up. The output of the crank sensor increases in amplitude, because it's a reluctance type sensor, and the ECU sees a readable signal and things return to normal. Close the throttle, the rpm drops, and the symptom reoccurs.

    To see if you are getting a crank sensor code you need to read the codes with the engine running on a 2.7 car. And in this case the car would need to be idling because that is when the problem appear. 2.7 cars will always show a crank sensor code if coded are read with the engine off.

    It could happen.
     
  16. Qavion

    Qavion F1 World Champ
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    So the SDL is not just an indication of high temperatures? Does bank shutdown for any reason illuminate the SDL?
     
  17. yelcab

    yelcab F1 World Champ
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    Nov 29, 2001
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    Mitchell Le
    Ian,

    The flashing SDL does not shut down the bank.
    The steady SDL does not shut down the bank unless you continue driving the car, then it shuts the bank down.
    The bank can be inoperative for a number of other reasons that have nothing to do with the SDL, for example, bad fuel regulator, fuel block lines swapped, bad coil, etc.
    On this car, 2.7, there is only one O2 sensor pre-cat and therefore no need or no place for an O2 sensor extender.

    As for the problem, focus on the reason for the SDL to come on. Use a DVM, or use a laser thermometer. It should be pretty logical: Thermal couple, TCU unit, wirings, bad ground, or ECU.
     
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  18. Qavion

    Qavion F1 World Champ
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    Thanks, Mitchell.

    Good point :p

    This would at least confirm the problem is real (temperature) and not a signal problem.

    Nick (London), could I ask how much you know about the operation of the engine. I'm not sure if you will simply pass on this information (piecemeal) to your technician or try to attempt to fix this yourself with some off-the-shelf tools (Voltmeter, laser thermometer, OBD2 reader, etc) and try to save a little money. It sounds like the car is still in the shop.
     
  19. johnk...

    johnk... F1 World Champ
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    I can not see this as a temperature problem. The SDL comes on and off in sync with the variations in RPM, below 1000. The flashes are not uniformly spaced in time as they would be for a temperature related signal. Additionally, the cats have thermal mass and the temperature isn't likely to respond that fast, nor would the TC respond that fast if the temp was. TCs do not have fast transient response. And once the RPM gets steady, above 1000 the SDL stays off.

    If the signal from the crank sensor is not within the acceptable voltage range (not too small and not too big) the ECU won't recognize the signal. . Under such circumstances it will think the affected bank is not rotating and it will turn off the injectors. I am suggesting that this might be the case and that maybe this would also cause the SDL to flash when the rpm drops.

    Regarding an MAF problem, I suffered a bad MAF last summer. The symptoms were somewhat similar in that the car would idle poorly, would almost stall, but with judicious application of throttle the RPM would rise and the engine would run marginally with a loss of power and poor throttle response. However, it did not cause the SDL to come on at all, but the check engine light would come on and go off periodically.

    Sorry if this seems far fetched but hanging around here for years I've seen many problems and the same old suggestions of what the cause may be which typically don't solve the problem. A little out of the box thinking may be required. I offer the 1448 code one 5.2 car. You would think by now someone would be able to point to the cause, but no.
     
  20. Qavion

    Qavion F1 World Champ
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    Understood, but what I was trying to hint at was that SDL (by design) appears to be only related to cat temperature. I don't see anywhere in the workshop manual or driver's handbook about the light being illuminated for other causes of bank shutdown/failure.

    It's hard to tell from that 10 second video what's going on, but I see a flashing light at idle, so you wouldn't expect bank shutdown. John has a good point about temperature hysteresis.
     
  21. m.stojanovic

    m.stojanovic F1 Rookie
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    It seems that the TC was intermittent when exposed to vibration (good when bench tested as there is no vibration). On the 355, the SDECU will produce high voltage not only at high temperature but also if the TC is disconnected from it. The vibration may cause short intermittent breakages of the voltage signal from the TC causing the voltage from the SDECU to spike (and the SDL to flash intermittently).

    In the case of NickLondon's problem, I would take Bob's suggestion as the first thing to check, i.e. check the voltages from the SDECUs and then replace the TC if voltage spikes are found. It is possible that the problem appears only at idle because the vibrations are greater at idle and the problem disappears at higher rpm because the engine smoothens-out and, with less vibration, the TC holds.
     
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  22. fatbillybob

    fatbillybob Two Time F1 World Champ
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    Aug 10, 2002
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    Vid not long enough and ditch the Muzak. Does it idle nice then stutter then blip throttle and it levels out nice or nice then go back to stutter? Stutter ever at cold start up? What about hot startup? If hot and stutter if turn off and restart what happens?
     
  23. Beetle

    Beetle Formula Junior

    Apr 10, 2013
    776
    All I hear is the Radio!!!!!
     
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  24. Tommy J.

    Tommy J. Karting

    Apr 7, 2016
    67
    Norway
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    Tommy Songkran Johns
    My 348 did a similar thing a couple of years ago when I bought it.I had one of the banks shut down a split second at idle, but couldn't tell which side so swapping parts on the banks didn't tell me anything. I had no error codes. I tried out a lot of stuff, and I don't even remember everything I did. But the one thing that fixed everything was when I disconnected and took the fusebox in passenger footwell apart. Went over all connectors and wiring. I found a few suspicious wire connections, but nothing obvious. Cleaned up everything and made sure all connections were good. The engine has not made a single miss ever since. It's not clear to me exactly what wire connection it was, but I suspect power supply to ECU, fuel pump or something like that. It made one of the banks shut down and restart immediately. No issue when driving or anything else than idle. Image Unavailable, Please Login Image Unavailable, Please Login

    Sent fra min SM-G935F via Tapatalk
     
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  25. m.stojanovic

    m.stojanovic F1 Rookie
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    Very good suggestion, good to have more ideas/experience.

    Some other posts, however, are useless!!!!...just to say something.
     

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