Misfire after Test Pipe install, help! | FerrariChat

Misfire after Test Pipe install, help!

Discussion in 'Technical Q&A' started by MufflerMan, May 29, 2006.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

  1. MufflerMan

    MufflerMan Formula 3

    Jun 12, 2005
    1,564
    Sacramento Ca
    Full Name:
    Colby Sandman
    I just bought a 328gtb and removed the cat and put a Borla muffler on it. Now I have a random misfire, anyone else experience this? I can't imagine it threw the mixture off enough to cause this problem, but maybe? Any help would be appreciated.
     
  2. mike

    mike Formula Junior

    Nov 2, 2003
    721
    Colorado
    Full Name:
    Mike
    I posted this under the tubi vs capristio thread in this area & didn't get a response..seems you have answered a part of my question..


    No replies, anyone have a comment?.

    Ok so now I've checked out a local shop that does mandrel bending. I have a 328 USA spec car with the single pipe, (the front header and rear header go into one pipe which goes to a cat con & into the muffler).
    I am not opposed to getting the mandrel bending done on alternative pipes, but don't want to do any fab work on the stock system (may want it back on in the future).
    So my question; if I go to the euro style exhaust (twin exhaust/one itermediate pipe for the front bank header & one intermediate pipe for the rear bank header, & if I maintain my O2 sensor & temp. probe on the intermediate pipe for the rear bank will this effect the readings on the O2/temp probe sensors (since they are normally reading the exhaust volume from both banks?).

    I read that another member had this problem when the O2 sensor or thermo sensor were off a test pipe,,(something to that effect)
     
  3. No Doubt

    No Doubt Seven Time F1 World Champ

    May 21, 2005
    72,740
    Vegas+Alabama
    Full Name:
    Mr. Sideways
    Some fcar owners have had good luck strapping their thermo sensor to the outside of test pipe, but no way will the test pipe get as hot as a cat...and that may negatively affect some fuel injection systems that depend on a heat reading to go from open loop (typically the very rich start up or full throttle conditions) over to closed loop mode (normal driving when the engine is warm).

    Too much fuel (i.e. systems thinks "engine is cold" when the engine is really warm) could easily cause a problem.

    This problem has been discussed a few times here on fchat, and I'm fairly sure that on the 348 the heated O2 sensors give the "engine warm" or "O2 sensor is warm" signal to allow closed loop ECU driving.

    I don't know about your 328. Perhaps it's the O2 if it has 4 wires, but not if it only has 3...otherwise it would likely be a thermo sensor or water temp sensor if your ECU system does any closed loop modes.

    Also keep in mind that it could just be that something that was wrong with the car when it had less power (e.g. cats on) may now be showing itself.

    To eliminate that possibility I'd suggest temporarily re-installing your cat/s just to see if that causes the problem to go away without doing *anything* else.
     
  4. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
    Owner Rossa Subscribed

    May 4, 2001
    35,280
    Birmingham, AL
    Full Name:
    Tommy
    I did mine that way. It never had a problem either. I just used a big metal clamp like one from a radiator hose. It gets pretty hot.
     
  5. No Doubt

    No Doubt Seven Time F1 World Champ

    May 21, 2005
    72,740
    Vegas+Alabama
    Full Name:
    Mr. Sideways
    Makes sense. Perfect solution. Cheap, too!
     
  6. Llenroc

    Llenroc F1 Rookie
    Rossa Subscribed

    Jun 9, 2004
    4,770
    Colorado
    Full Name:
    Vern
    How many times do we have discuss this. The exhaust temp probe and its ECU have nothing to do with engine management ECUs other than to tell it when it thinks the cat is over heating. It is an independant warning system to trigger the slow down lights for an over heating cat. The temp probe ECU is only connected to the Motronic systems ECU to shut off injectors when it thinks a cat is out of temp range and only for this reason will it effect the operation of the engine ECUs, the temp probe is even more independent in CIS system because it doesn't shut down the injectors. It does not affect mixture on Motronics or the Bosch CIS systems(328). What effects open and closed loop is mainly the coolant temp sensor, throttle position and/or the 02 temp circut, never the exhaust temp probe and its ECU. If the cats have been removed than remove the cat sensors and the warning lights as they serve no purpose. Regards, Vern
     
  7. KurtK328

    KurtK328 Formula Junior

    Mar 6, 2001
    347
    Villeneuve-Loubet, France
    Full Name:
    Kurt Kjelgaard
    Well said, Vern
    Mufflerman, check your ignition wires.
     
  8. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
    Owner Rossa Subscribed

    May 4, 2001
    35,280
    Birmingham, AL
    Full Name:
    Tommy
  9. Birdman

    Birdman F1 Veteran

    Jun 20, 2003
    6,687
    North shore, MA
    Full Name:
    THE Birdman
    I don't know much about the CIS on a 328, but it would seem to me that if you removed a restriction in the exhaust, you might need to tweak the mixture a tad to richen it up. I know CIS is self-adjusting and all that, but it still has a manual mixture control.

    A misfire is often the result of a lean condition, and this is almost certainly what would happen with the removal of the cats.

    Birdman
     
  10. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,038
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    vern -- No argument that that is the situation on Motronic, and that on the K-Jet without Lambda and the KE-Jet with or without Lambda, the warning light system is not connected to the engine management system at all, but have you ever measured what is happening on pin 4 of the warning light ECU (that connects over to pin 6 on the injection ECU) on a F K-Jet with Lambda system? None of the other Bosch CIS systems have this connection (and pin 6 is the injection ECU connection that also monitors/uses the idle/WOT switch input signal). Do you have any measured information or observations that prove that the warning light ECU pin 4 signal does not affect 328 injection operation? (Not trying to argue, but I'd like to know more -- and I don't have a 328 handy to measure ;))

    Colby -- same sort of question to you -- have you tried to verify that the O2 sensor output is reasonable/unchanged/similar for the two configurations? And can you confirm that your current situation with the Borla muffler is:

    1. the O2 sensor is mounted as close as possible to where the exhaust flows from the two headers are joined together, and

    2. the thermocouple is still electrically connected but just mounted/stored in free air?

    Or please clarify/describe the physical arrangement, if different.
     
  11. Llenroc

    Llenroc F1 Rookie
    Rossa Subscribed

    Jun 9, 2004
    4,770
    Colorado
    Full Name:
    Vern
    Hi Steve, Hey no argument taken, its fun for me to figure this stuff out. I have not measured the voltage on those wires but in all of the Fcar shop manuals and Bosch manuals I can't find anything that relates to the temp probe ECU being tied to the CIS system in a way that controls anything with engine management. That being said and that CIS system being mechanical what could it effect? I guess it could be tied to the lambda sensor by interupting that signal and turning on the CEL but you wouldn't think that would make it miss just go into open loop, correct? Since the injector system is mech. that couldn't shut down the injectors as on the Motronic systems, this being the way to cool down the cat on the motronic. The lambda probes on the CIS are fairly limited in it operation, only fine tunes the mixture to keep it at that glorious 14.7:1 ratio so, I wouldn't think that open loop on the CIS system would create a miss, (CIS referring to input based on the pre set fuel delivery) might run slightly rich or lean but not bad enough to make the engine run so bad it would it would miss. Even if you disconnect the probe its ECU would think the probe is cold and not too hot as to trigger the the slow down light.
    I have always found that if the exhaust temp probe and ECU are functioning correctly you could remove the probe from the pipe and it would not reconize that it was disconnected no lights no engine miss everything is normal. But, these comments are limited to what I have encountered related to a few cars I have been involved with over the years. Regards, Vern
     
  12. No Doubt

    No Doubt Seven Time F1 World Champ

    May 21, 2005
    72,740
    Vegas+Alabama
    Full Name:
    Mr. Sideways
    Vern, you seem to be under the impression that no Ferrari engine management system modifies fuel/air mixtures based upon exhaust temp readings (e.g. open loop when engine cold versus closed loop when engine is warm).

    Therefor if someone simply removes the exhaust cat temp sensors per your recommendation above, one can safely say that said removal won't cure the misfire that they are complaining about.

    I think that the better path to recommend is to suggest that he temporarily re-install his cat. If the misfire then goes away, the problem has been isolated to the cat/sensor. If the problem is still there, then removing the cat in the first place wasn't the cause.

    That would get him useful information either way.
     
  13. smg2

    smg2 F1 World Champ
    Sponsor

    Apr 1, 2004
    15,475
    Dumpster Fire #31
    Full Name:
    SMG
    on KE systems the Lambda and other sensors do control the pressure control on the fuel disributor. the earlier non Lambda CIS does not have this control. the O2 sensor sends it signal to the control box and from there the lamda valve controls the pressure on the control pressure regulator.

    if you remove that O2 sensor then you lose that control.
     
  14. Llenroc

    Llenroc F1 Rookie
    Rossa Subscribed

    Jun 9, 2004
    4,770
    Colorado
    Full Name:
    Vern
    I think that is already understood here its not the 02 sensor that is in question its the temp probe that is in question here. I can't find any relation of the temp probe to the CIS system on the 328. Regards, Vern
     
  15. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,038
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    Vern -- No disagreement from me that a K-Jet with Lambda system that is working well (and is tweaked-up reasonably) should run perfectly OK either open-loop or closed-loop (if the O2 sensor is mounted in a reasonable place), but I can't yet accept that as proof that the signal placed by the warning light ECU pin 4 onto the injection ECU pin 6 has no effect at all (even if the apparent runability to the Driver seems unchanged).

    Anyone know which F model had the first K-Jet with Lambda system? MondialQV? Would that particular WSM have any more detailed system information?
     
  16. Llenroc

    Llenroc F1 Rookie
    Rossa Subscribed

    Jun 9, 2004
    4,770
    Colorado
    Full Name:
    Vern
    The US 308s from 1980 thru the 328 series used that K-jetronic system. If the temp probe effected anything wouldn't it be to shut down the fuel delivery only as in the motronic system? More of a rhetorical question I guess. I have a bosch manual around here somewhere I do some digging and see what I can find. Regards, Vern
     
  17. Llenroc

    Llenroc F1 Rookie
    Rossa Subscribed

    Jun 9, 2004
    4,770
    Colorado
    Full Name:
    Vern
     
  18. No Doubt

    No Doubt Seven Time F1 World Champ

    May 21, 2005
    72,740
    Vegas+Alabama
    Full Name:
    Mr. Sideways
    Vern, if the Lambda frequency valve controls the variable fuel pressure, then wouldn't it be up to the exhaust temp ECU and lambda ECU to vary fuel pressure based upon exhaust temp?

    I mean, unless we know how the exhaust temp ECU and lambda ecu work internally, do we really know if they are only shutting off fuel at a certain exhaust temperature versus varying fuel pressure?
     
  19. smg2

    smg2 F1 World Champ
    Sponsor

    Apr 1, 2004
    15,475
    Dumpster Fire #31
    Full Name:
    SMG
    Vern, sorry i thought the O2 was in question.

    it is interesting that the earlier CIS cars have the temp probes but only as a failsafe to alert the driver to a problem with the cat. i would think with the later KE-Jetronic that the temp probe could be programmed into the control unit to cut fuel or run it in 'closed loop'. the Bosch books i have say to refer to your manufactures data for specific on sensors and how they are programmed. to me that leaves room for the manufacture to add additional sensors and controls. if ferrari did, that reamins to be the question.

    i guess you could test it on a chassis dyno. read the exhaust gas under OEM specs then remove the probes and run again to see if the ECU cuts/adds fuel or modifies it in some way. or conversly heat the probes artifically to see what happens.
     
  20. No Doubt

    No Doubt Seven Time F1 World Champ

    May 21, 2005
    72,740
    Vegas+Alabama
    Full Name:
    Mr. Sideways
    Absolutely...or you could just re-install the cat to see if the misfire goes away!
     
  21. Llenroc

    Llenroc F1 Rookie
    Rossa Subscribed

    Jun 9, 2004
    4,770
    Colorado
    Full Name:
    Vern
    The systems use water temp sensors for any temp info they need not exhaust temps. You sorta have to look at the bosch books and diagrams to this and read their theory on how and why their systems work the way they do. Remenber Ferrari is the only one to use this exhaust temp probe concept and only to shut off fuel flow in an over heated cat concept. On your second sentance they are varing fuel presure by shutting it off I think that is what you are asking?? I don't know what else to say about it, I have exhausted(no pun intented) my sources on this. Regards, Vern
     
  22. No Doubt

    No Doubt Seven Time F1 World Champ

    May 21, 2005
    72,740
    Vegas+Alabama
    Full Name:
    Mr. Sideways

    Vern, you may very well be right. I honestly don't know.

    However, I find a few things that make your explanation (which I re-emphasive, could be correct) difficult to accept:

    #1, the heat temp system is wired to the lambda ecu that varies fuel pressure

    #2, some of these K+Lambda cars that remove cats get misfires, and

    #3, some of the K+Lambda cars that remove the cats while strapping the heat temp sensor firmly to the test pipe seem to run fine.

    CopterJon had a thread recently in which re-installing his cat solved the misfire that he got when he removed said cat earlier, too. EDIT: http://www.ferrarichat.com/forum/showthread.php?p=135776534#post135776534 (see post #1 - removed cat ---- and post #5 - re-installed cat)


    I do like the approach that you and 91TR are taking; going back to the manuals and available external circuit diagrams.

    My approach at the present is more simplified; re-install the cat (and heat sensor!), I say, to see if the problem goes away.

    Italian documentation leaves something to be desired. That being said, I'd be happy to give a definitive answer to this if someone can provide me with the internal circuit diagrams and/or firmware code (if it is in use in such devices) for these systems.

    Other than that, it seems to me that re-installing the cat would provide the same answer (potentially).
     
  23. smg2

    smg2 F1 World Champ
    Sponsor

    Apr 1, 2004
    15,475
    Dumpster Fire #31
    Full Name:
    SMG
    i can't see the temp probes varying the fuel rate as the lambda does. it would seem most likely if it was tied into the ECU that it would be set for a specific resistance like a switch and at the predetermined heat range it would signal the ECU that the cats are too hot. to have it react like O2 sensors would be reduntant. O2 senors on thier own should be control the fue lso as not to overheat the cats. the probes would be more like the last minute fail safe and cut fuel to avoid a fire.

    we may never know unless we have the schematics on what ferrari designed.
     
  24. KurtK328

    KurtK328 Formula Junior

    Mar 6, 2001
    347
    Villeneuve-Loubet, France
    Full Name:
    Kurt Kjelgaard
    The 328 (and the Mondial3.2) has the KE3-Jetronic system and therefore, as 91TR mentioned earlier, there is no connection between the Cat temp warning light system and the fuel injection system (other than sharing a ground connection).
    I still suggest a check of the ignition wires - coincidence sometimes kicks in and I believe that's what happened here.
    Keep us posted - with these cars we all might be wrong.................
     
  25. jaydens1

    jaydens1 Rookie

    May 17, 2006
    33
    new zealand
    Full Name:
    tony j downes
    agree with smg2 about regulator.disconnecting them can make ECU go into a limp mode situation.why dont you weld threaded connectors into your new pipe in a similar position as your old pipe and retry/is the 02 sensor ok/is this problem on light accelleration/does it have an o2 sensor /is the heat sensor or wiring damaged/has something else been knocked or damaged
     

Share This Page