| Author | Message | ||
| Lloyd (Lloyd)
Junior Member Username: Lloyd Post Number: 62 Registered: 8-2001 |
Assuming cats are replaced with test pipes and all else remains the same, are the thermocouples necessary for proper engine management. The reason I ask is that if I replace the precat pipe, in a system with no cats, with another set of pipes with no thermocouples, will this negatively effect engine management? Or in other words, do the thermocouples really have any use in normal engine management absent a cat. | ||
| Jim DeRespino (Jimbo)
Junior Member Username: Jimbo Post Number: 75 Registered: 10-2001 |
Rob: thanks for the reply. This is so cool. Where does the code flash - the MIL ("check engine") itself, or somewhere on the ECU? When you say it flashes in "tens and ones" do you mean that 6 flashes followed by 4 flashes means 64? I always knew ferraris were special, but I never thought mine could talk to me... | ||
| Rob Schermerhorn (Rexrcr)
Member Username: Rexrcr Post Number: 476 Registered: 11-2002 |
If it's a US spec car, there is a diagnostic button located close to the ECU's. Press and hold >10 seconds. The respective MIL will begin flashing, first to confirm diagnostic mode, then any stored error codes. Flashed in "10's" and "1's" two-digit codes. This info should be in the WSM. Ignore the code for crank pickup, this simply means the engine is not running at the time. After viewing, codes can be cleared via diagnostic button too. If you disconnect the battery, all codes are cleard and the ECU's must "relearn" baseline parameters by idling the engine for a few minutes with no throttle input. Typically I recommend running until cooling fans come on. Jim, 512TR does have "balast boxes", but they are actually a box of potted electronics commonly refered to as "thermocouple ECU". This box changes the thermocouple data into engine ECU readable voltage. | ||
| Jim DeRespino (Jimbo)
Junior Member Username: Jimbo Post Number: 74 Registered: 10-2001 |
Jim S: The thermocouple ECU's were disconnected 2500 miles ago because it was inappropriately shutting down the 7-12 bank. I noticed no change in performance. I think the problem this time in in the O2 sensor/wiring Rob: I have the workshop manuals and am intrigued by the self-diagnostic capabilities of the Bosch Motronic 2.7. Can you explain simply how it works? | ||
| Jim DeRespino (Jimbo)
Junior Member Username: Jimbo Post Number: 73 Registered: 10-2001 |
I checked the O2 sensors and they were tight in the test pipes, so I unplugged the connectors (2) from the O2 sensor to the wiring harness, uttered some quasi-Italian words of enchantment, added a little dielectric grease and plugged it all back together. Guess what - no more MIL. I took the car out for our monthly ferrari dinner (35 min each way)- no more MIL. Will it return? Is the O2 sensor beginning to fail? Is it merely a bad connection? Only time will tell. I have a 7 hour (each way) trip next month, and I am now armed with diagnostic schemata up the ying-yang, so I'll keep you posted. Thanks to all f-chatters for your valued input. BTW Brian, I could not find any ballast boxes on the 512TR - are they a testarossa feature? | ||
| Rob Schermerhorn (Rexrcr)
Member Username: Rexrcr Post Number: 469 Registered: 11-2002 |
Agreed, sometimes confusing. IME, coolant (NTC sensor(negative temperature coefficient)), oil, air temperature: thermistor. Exhaust: thermocouple. Back to subject of thread: we really need to know the error code, otherwise this is just educated guessing. | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 473 Registered: 6-2002 |
Rob - agree that the thermister (thermocouple) continues to work in the absence of the cat guts. I was merely suggesting that the purpose of this particular electronic system was to warn the driver of a potential fire hazard due to overheated catalytic converters. Since Jim R. does not have catalytic converters, and he is having difficulty with the light, why not disconnect the acrylic ECUs to turn off the light? The aformentioned diagnostic test of switching the thermister sensing cat temperature for Bank 1-6 with ECU for bank 7-12 will tell you whether the difficulty is at the level of the transducer, or the ECU. Without the cat, it simply does not matter. Rob - your data concerning the resistance/temperature relationship is great (and available in the WSM). It does allow one, with cats in place, to diagnosis and treat. Thanks. BTW - I am not sure whether automobile temperature sensors are thermocouples, or thermisters. Different technological approach to measuring temperature. The schematic sometimes shows a variable resistor for a temperature sensor, suggesting thermistor, while at other times it reveals two wires, suggesting a thermocouple. Anyone know? Jim S. | ||
| Rob Schermerhorn (Rexrcr)
Member Username: Rexrcr Post Number: 462 Registered: 11-2002 |
Jim, my first though, other than doing a proper step-by-step diagnosis, is you have a lose connection causing the MIL. Knowing what the actual fault code is will be very helpful, you can do this yourself as you have Bosch Motronic 2.7 self-diagnostic capability. The codes flash using the MIL light as stated in your WSM. If you don't have the WSM, stop guessing and buy it first. Also get Bosch Handbook and Bosch Electrics/Electronics here: www.sae.org. James, the thermocouples send temperature data to the ECU via the thermocouple ECU's you mention. If you gut your catalysts, the thermocouples still work, no need to disconnect unless the thermocouple ECU is defective and trips an error code. You can actually tap into this circuit and use the temperature data if you want, you only need the response curve, which is data I posted a month ago for 2.7 and 5.2 Motronic. I agree, swaping connectors bank-to-bank is usually an easy troubleshooting technique. | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 472 Registered: 6-2002 |
Jim R. - This is how it works on my 1986 Testarossa. If you have "hollowed out" your cats, then your thermisters (temperature sensors) are doing nothing. Disconnect the epoxy boxes that the metal-braided wires run to. They are sending an erroneous signal to your "Slow Down" light. Good luck. Jim S. | ||
| JRV (Jrvall)
Intermediate Member Username: Jrvall Post Number: 1234 Registered: 11-2002 |
>>Do the O2 sensors send input to the ECU's or affect the fuel curve in any way?<< yes they signal the ECU's and affect the ECU's varying of injector pulse width (mixture). However, if one goes bad it doesn't mean the engine will run poorly (to a degree) as the computers have back-up parameters (Fuel/Ignition mapping) built in. But they will trigger the MIL's (Malfunction Indicator Lights). Additionally, you stated that the problem is short term & sporadic, so it seems that something that will trigger a MIL is coming & going in the system, something that will trigger a MIL, but won't affect performance short term . That's why I suggested what I consider to be a viable "starting point" = Oxy Sensors. >>>> I have just been back and forth from Sebring Raceway (FCA National Meet) twice (150 miles each time) and now the light comes on when I hit a bump or make a hard turn and stays on for 10 -15 sec. The car ran perfectly, average speed 80 (with several quick jaunts to 140) and got 13 mpg. The engine never missed, all gauges spot-on. I have the thermocouple ecu's disconnected since I have test pipes and hollowed-out pre-cats<<< | ||
| Jim DeRespino (Jimbo)
Junior Member Username: Jimbo Post Number: 72 Registered: 10-2001 |
JRV, I understand and will check the O2 sensor (these are still in place). Do the O2 sensors send input to the ECU's or affect the fuel curve in any way? Manu and Heiko, the cats are gone and the thermocouple ECU's are disconnected. Brian and James: does this apply to the 512TR as well as the earlier TR's? If the O2 sensor does not affect the running of the engine I will disconnect the ballast boxes. Since the pre-cats are hollowed out and the cats are replaced with test pipes, excessive exhaust temps should not be a problem. Hopefully I would be able to feel/hear a dead cylinder, and the car ran fine up to 140 mph and idles like a purring kitten. Thanks to all for the wise advice. I will perform the suggested diagnostics in the AM and let you know. | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 469 Registered: 6-2002 |
Brian is right on. Follow his advice to the letter. I have done this to diagnosis a bad control unit. As a general rule, if the car is running fine, then it is unlikely that you are suffering from excessive catalytic converter temperature. The sensors and warning lights are there to alert you should your fuel injection be pumping too much gas (rich mixture) to the point that excessive fuel is not burned where it should be, and ends up burning in the catalytic converter. If the car is running well, without electric fault leading to dead cylinder bank, or several dead spark plugs, then you are not going to overheat your cat. Jim S. | ||
| Brian Willis (Lmpdesigner)
New member Username: Lmpdesigner Post Number: 9 Registered: 11-2002 |
Standing behind the car, look at the right hand (passenger)side of the engine compartment. You should see a metal access panel about even with the middle of the motor, at about cylinder head height. Pull this cover (2 bolts I think) and find the exhaust temp sender ballast boxes. They are whitish lumps of porcelain/ceramic with wires going in and out. There is one each for cylinders 1-6 and 7-12. Notice they stainless braided wires going out to your exhaust (whether hooked up or not to the exhaust is not relevant-trust me!) Now take and swap the wires coming out of the ballast box (The ones with the plastic rectangular connectors). Now run the car and see if the warning light swaps from cylinders 7-12 to 1-6. (Remember-you have swapped output wires.) If the warning light swaps-congratulations-you have a bad ballast box! If he problem stays with cylinders 7-12 then you have a bad ground input from the stainless braided cable that goes to the exhaust or a bad sensor. The ballast boxes are big bucks-cannot remember price. The real solution is to simply unplug the ballast boxes completely or remove them and ignore the problem. The car will run fine whether the light stays on or not. You can find more information about this at the Ferrari Club of America website's technical forum (http://www.ferrariclubofamerica.org), go to the V-12 section and look for the "slow down warning lights on 87 TR" post. | ||
| JRV (Jrvall)
Intermediate Member Username: Jrvall Post Number: 1226 Registered: 11-2002 |
>>>the cats are removed, test pipes are installed in their place and the thermocouple ecu's are disconnected.<< I read it fine the first time. So what are you saying??? You don't have Oxy Sensors either? Not impossible, but hard to believe. | ||
| Jim DeRespino (Jimbo)
Junior Member Username: Jimbo Post Number: 71 Registered: 10-2001 |
Thaanks for the advice, but read the original post - the cats are removed, test pipes are installed in their place and the thermocouple ecu's are disconnected. | ||
| Heiko (Hgparts)
Junior Member Username: Hgparts Post Number: 76 Registered: 3-2003 |
looks like the ecu for the cats is broken often the problem on the 348 and 355 too | ||
| Manu (Manu)
Member Username: Manu Post Number: 689 Registered: 2-2002 |
The previous diagnoses are correct..... could also be that your cat is f**ked.. If it's the case that your thermocouple is damaged (excessive cat temps), then to put paid to this problem permanently buy some test pipes (and a new thermocouple)  ! | ||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 1611 Registered: 1-2001 |
(deleted) | ||
| JRV (Jrvall)
Intermediate Member Username: Jrvall Post Number: 1225 Registered: 11-2002 |
Check your Oxy Sensor wires/plugs & tightness into test pipes.. >>now the light comes on when I hit a bump or make a hard turn and stays on for 10 -15 sec<< sounds like the 7-12 oxy sensor may be loose or loosing ground. | ||
| Jim DeRespino (Jimbo)
Junior Member Username: Jimbo Post Number: 70 Registered: 10-2001 |
For the last few weeks, the "check engine cyl 7-12" light would come on momentarily after the first left hand turn after start up. I have just been back and forth from Sebring Raceway (FCA National Meet) twice (150 miles each time) and now the light comes on when I hit a bump or make a hard turn and stays on for 10 -15 sec. The car ran perfectly, average speed 80 (with several quick jaunts to 140) and got 13 mpg. The engine never missed, all gauges spot-on. I have the thermocouple ecu's disconnected since I have test pipes and hollowed-out pre-cats. I now appeal to the ferrari gods for guidance. What else triggers this light? Should I be worried? By the way, they had 2 Enzos at Sebring and they are truly phenomenal. |