Hi Guys one and all, I have my car with the dealers to check why the "Slow Down"light comes on on the lower right corner of the dash when hoofing it near the red line. Now I know that might sound obvious, but it does it only when hot, and not all the time. I have a 99 355 F1 with Capristo 3 and removed the Cats for straight through pipes. One consideration could be the depth that the sensors are going into the flow of exhaust gasses. The agents do not pick up any error codes with their computer. I suggested to them that they come to the track and plug the machine on and then get on the track. It is irritating knowing that I have not got tot he end and it tells me to slow down, surely there should be a margin of getting to the rev limiter anyway. All the engine peramiters appear normal. Just a thought if the sensors were shimmed so not to protrude too much it might help. Anybody able to measure how much they protrude would be helpfull. Thanks in advance
One or both of your cat temperature ecu's is shot. If you are running straight pipes there is no way that you will get an over heated cat. Run a search of the archive on the subject to learn more. But in short just disconnect the damn things. The car will run fine with them disconnected. The only thing is that the Motronic ecu will store a silent code that says the cat ecu is disconnected, but the car will still run just fine.
One possible rectification I have been given on this problem would be to place a deflector infront of the aft sensor to deflect the hot gasses around the sensor thus reducing the temperature slightly and in so doing allow there to be a diferential between the front and rear probe temperatures.Any thoughts???
That's a bunch of bull. First of all the thermocouple takes the temperature of the exhaust gases from INSIDE the catalytic converter, so you can put all the shielding you want around it and it still will not matter because the thing is INSIDE the cat. You said that you are running test pipes right? Well the test pipes DO NOT MAKE HEAT, because there is not catalyst to get hot from unburned gases. So................there isn't any way for the thermocouples to get hot, nor for the cat ecu's to get a hot signal from the thermocouples. The only way the the cat ecu will get a hot signal is if the thermocouple sends it. If the TC is sending a hot signal and you DO NOT have a cat, then the TC is bad. The only way that the Motronic ecu will get a hot signal, and thus give you a slow down light, if if the "cat"alytic converter temperature ecu sends it a signal. Again, if you have NO CAT there isn't anyway that it can get hot, so........................ Either your cat ecu is whack, or the thermocouple is whack. All you have to do is unplug the cat ecu's and drive the car. Which will cost you nothing, zip, zilch, nada = free. If these guys are telling you to put a "shield" around the thermocouple something smells reeeeeeeeeeally fishy????? Capiche? Heck, you can even pull the thermocouples completely out and then cap the hole if you want. Because you are not running any cats.
Will disconnecting the CAT ECU's on the 5.2 motronic do nothing more than throw a silent code? In other words, will this eliminate the slow down light all together, or will you at least get the blinking slow down light? I ask because I've removed my cats in favor of test pipes and I'm now receiving codes 1445 and 1449 which (if I'm not mistaken), are left and right thermocouple/CAT ECU errors.... as well as the blinking slow down light. I can clear the motronic of codes, drive for approximately 15 minutes, and get the blinking slow down light. Thanks, Nick
