| Author | Message | ||
| Bill White (Nc_newbie)
New member Username: Nc_newbie Post Number: 40 Registered: 2-2003 |
I think that unplugging the Thermocouple ECU is better than removing the light. The orange/yellow stripe wire not only goes to the slowdown light but also to the main engine ECU according to the diagrams. Therefore I was concerned that if the ECU thought their was a problem it may change something (like lean it out). Therefore unplugging the Thermo ECU make eveything to the main ECU appear normal. Where as just removing the light would still leave this signal going between the two ECUs. | ||
| Ronald Vallejo (Ron328)
New member Username: Ron328 Post Number: 14 Registered: 3-2003 |
Jscott...thanks, too. To tell you the truth that's what I'm thinking! (Easy fix for this aggravation!!). | ||
| Ronald Vallejo (Ron328)
New member Username: Ron328 Post Number: 13 Registered: 3-2003 |
Thank you Carl and Bill. I have a few more questions (that will reveal my ignorance of the subject). I think I understand the preceding though. (Incidentally, I remember this blinking red light when I test-drove the car prior to purchase and the dealer fixed it before shipping the car to me). 1. When the ECU fails, how does this affect the engine or the car itself? 2. I'm in Missouri (about sea level) and my 328 was originally from Salt Lake City (above sea level). I was told that the air fuel mixture may have to be adjusted (ie., optimized). This I haven't done yet although I was told it's not a big deal. Could this cause #3 (too rich mixture)? 3. So long as that red light is off, can I still drive the car, or am I in danger of breaking down? (note: On my way home, I drove the car uneventfully for about 60-70 miles w/o that red light blinking) Thank you so much. | ||
| j scott leonard (Jscott)
Member Username: Jscott Post Number: 317 Registered: 1-2002 |
Take the light out. Works every time. | ||
| Bill White (Nc_newbie)
New member Username: Nc_newbie Post Number: 39 Registered: 2-2003 |
One other thing I picked up from a manual. Blinks at 850 deg. Comes on steady at 900 deg. Sounds to me like a faulty thermocouple. Measure the resistance of your thermocouple cold and at temp. Also it would help me verify my design to know the voltages you get on the orange/yellow striped wire from the thermo ECU under these different scenarios. I think the ECU for Motronic system in 348+ is different from the older K-jet systems in 3.2 and earlier. | ||
| Bill White (Nc_newbie)
New member Username: Nc_newbie Post Number: 38 Registered: 2-2003 |
I'm an electronics design engineer and have been looking into this as I have the same problem on my mondial 3.2. Seems like from what I can tell there are 4 things things that cause this light to come on (in order of probability): 1. ECU failure 2. Thermocouple resistance out of range 3. too rich mixture (fouled plug for example) 4. cat temp too high (the reason the f-in light is there) I bought a new ECU from GT Car parts for $225. Put it in. It worked as designed for about 100 miles then went out. The guys at Gentry lane then measured the resistance on a new thermocouple for me. At room temp it was about 5.2 ohm. Mine was 0.4 ohm and at idle op temp about 1.5 ohms. I think I have both a bad thermocouple and now bad 2 week old ECU. I would advise measuring the room temp resistance and if it not about 5 ohms replace both the ECU and the thermocouple. If it is too low I have proven that you'll burn out the ECU. I have actually redigned a replacement ECU that I am thinking about building that would allow proper calibration rather than replacing both the ECU (again) and the Thermocouple. | ||
| Carl Rose (Carl_rose)
Junior Member Username: Carl_rose Post Number: 94 Registered: 10-2002 |
Hi Mr. Vallejo, Recent brief thread on this for Mondial 3.2 from 3/12/03. The "slow down" blinking/constantly lit is designed to be a function of excess converter temperature. That said, apparently ECU failure is more common than true exhaust problem. This turned up on PPI for my 328 (owner fixed by putting in new fuel?) FoH replaced ECU & no further dash light. Unfortunately don't know proper diagnostic algorithym for 328 (other models with 2 ECUs can simply switch) but I do have my old ECU; can measure "bad" - if not a function of temp - terminal resistance values for you. Drop me an email: [email protected] If this is the problem be forewarned: I think new ECUs run about $450? Hope this helps,  Carl | ||
| Ronald Vallejo (Ron328)
New member Username: Ron328 Post Number: 12 Registered: 3-2003 |
Hi all. Recently drove my 328...logged about 130 miles, mostly in the interstate. When I got into the inner city (speed limit under 40 mph, all those stop lights), the red "slow down" light started blinking. I really couldn't slow down any further as I was already driving slow because of the traffic. The blinking persisted for a few minutes and this happened on 2 separate occassions when the car was running slow. But when I got the car going again as I entered the highway, the blinking stopped. All those times, the car ran fine. Drove back home uneventfully. Should I worry now? Thank you. Ron |