| Author | Message | ||
| Darrell Pardy (Dpardyferrari)
New member Username: Dpardyferrari Post Number: 31 Registered: 8-2002 |
PROBLEM SOLVED!!! Through some diagnostic help from my mechanic in Massachusettes, I pulled all the spark plug connectors, made sure they were clean and then replugged them. I also remembered that part way through my trip home I had to use a mid octane fuel (87) because I was running low on fuel on a backroad in Maine. (Roads are great for driving but 90 miles without a decent gas station !!). So I let the car run down to 1/8 tank and filled it with 93 octane. I have now run it twice (about 30 miles each time), both times aggressively and no slow down light, car is idleing fine at 1200 rpm. So the lesson I learned is good gas is critical and keep checking for good fittings etc etc... I love the education I am getting from this ownership.  | ||
| dennis negherbon (Roofman)
New member Username: Roofman Post Number: 3 Registered: 9-2003 |
Just some follow up on this subject, upon further reserch, there seems to be a problem with the ECU on some Mondials and 348s. I have now had three different mechanics and two parts suppliers tell me that there has been quite a few up-dates for the ECU on these models. That it is quite common to have problems with their sensitivity and giving false readings. I don't know if the same can be said for other models, I'm just trying to pass along some additonal information. | ||
| dennis negherbon (Roofman)
New member Username: Roofman Post Number: 2 Registered: 9-2003 |
Thanks for the advice. | ||
| Mike Charness (Mcharness)
Intermediate Member Username: Mcharness Post Number: 1003 Registered: 8-2002 |
Dennis, Steve is right... you could potentially have a fire if you aren't careful. If the cat is "glowing" and that's the reason the slow-down light came on, you won't necessarily feel a loss in power. That happened to me probably 9 years ago after I first got my car, it drove just fine but indeed that cat was glowing hot. Thankfully, no damage, just had to replace the cat. | ||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 2118 Registered: 1-2001 |
dennis -- Yes, the thermocouple is mounted in the exit side gas stream of the cat. John -- The "Red Heat Range" for steels is ~1200 deg F to ~2000 deg F so at ~1600 deg F it should show a strong red/orange glow. (Everyone always seems to not stop when the slowdown light comes on and just try to take it easy and get home, but IMO the first thing to do is open the bonnet and do a visual check to see if the exhaust is glowing or not.) | ||
| dennis negherbon (Roofman)
New member Username: Roofman Post Number: 1 Registered: 9-2003 |
Would the thermocouple be located just behind the cat converter? I have a mondial t that is doing the same thing on the 5/8 side. I have also been told that the ecu sending unit could be part of the problem. The one located in the trunk. Just as long as you don't loose power when the light comes on, then it most likely is a sensor problem, at least I have been told. | ||
| John Wise (Jwise)
Junior Member Username: Jwise Post Number: 62 Registered: 4-2003 |
Dr., not on my car, but one I was looking to purchase before buying mine. Mine has no "slow down" lights at all. Steve, so if the cat is hot enough to set off the warning light, it is hot enough to glow? | ||
| Dr Tommy Cosgrove (Vwalfa4re)
Intermediate Member Username: Vwalfa4re Post Number: 1294 Registered: 5-2001 |
John, If you have the two square lights on the dash on each side of the steering wheel AND your car is an 85 they were definitely added by a previous owner. Do you still have the one up in the instrument pod too? | ||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 2117 Registered: 1-2001 |
Darrell -- Is the slowdown light self-test working OK every time? Next time the slowdown light comes on, stop the engine and have a visual look at the exhaust system near the thermocouple -- if the slowdown warning light system is working (and truly detecting ~1600 deg F temperature) the exhaust system near the thermocouple would be glowing red/orangish so that would confirm you've got a real problem and not an electrical gremlin. | ||
| John Wise (Jwise)
Junior Member Username: Jwise Post Number: 61 Registered: 4-2003 |
Weird- I looked at an 85QV (US) before buying mine and it had two slow down warning lights, one for each bank. Maybe the dash was replaced in the past. Mike- what would cause a cat to overheat other than poor running, or it being clogged? If the car runs fine, wouldn't it point to a bad sensor? Or, could it be running so rich to destroy the cat, and still run fine. | ||
| Mike Charness (Mcharness)
Member Username: Mcharness Post Number: 1000 Registered: 8-2002 |
Really... just one "slow down" light, as the temperature sensor (thermocouple) is in the single cat and wouldn't know which bank was contributing to the problem. | ||
| John Wise (Jwise)
Junior Member Username: Jwise Post Number: 60 Registered: 4-2003 |
Really? Is it just a single light on the dash instead of the dual 1-4, 5-8 slow down lights under the dash? Mine has two cats- but is a custom exhaust. Here's a picture. This is after replacing the cats and cleaning and paint. I decided to use cats again because I like how it sounded. It's actually pretty cool and sounds great:  Darrell, I'll contact you offline. We can get together sometime. | ||
| Mike Charness (Mcharness)
Member Username: Mcharness Post Number: 996 Registered: 8-2002 |
John, on the 84 308QV (at least the USA models) there is only ONE "slow down" light, as the car only has one cat. Earlier models had two cats. | ||
| John Wise (Jwise)
Junior Member Username: Jwise Post Number: 59 Registered: 4-2003 |
It sounds like, from your desription, that Mike is correct. Is it only one of the lights? If a cat is plugged, it will get warm. If there is raw fuel running into it, it will get very warm. It sounds like your car is running fine- just the warning light. No change in sound, or power? I live in Portland Maine also. If you want, I could help with this. If nothing else- an extra brain to try and figure it out. I just welded two new cats into my car because one was clogged. It's a euro 308, so there are no warning lights, so I cant tell you if a clogged cat warms up enough to set off the sensors.  Here is what the bad one looked like. I could hear it rattle around as I drove. Can't the sensors on the cats, (if you still have them) just be switched to see if the other light comes on? | ||
| Mike Charness (Mcharness)
Member Username: Mcharness Post Number: 993 Registered: 8-2002 |
The Slow Down light generally means that either it's a bad sensor (thermocouple) or your catalytic converter is overheating and needs replacement, presuming you still have it and it wasn't taken out when the Tubi went in. | ||
| Darrell Pardy (Dpardyferrari)
New member Username: Dpardyferrari Post Number: 28 Registered: 8-2002 |
I just returned from a 550 mile trip in my 1984 308QVi and about 500 miles into the trip the slow down light came on (solid). I pulled over and let the car cool down and nursed it the 15 miles left to the end of the trip. Light stayed on. Here is some other info: The car has a new Tubi exhaust, fully serviced, all guages look normal. Driving speed averaged about 75-80 mph. The next morning I checked all the spark plugs etc and restarted the car. It started fine and soon eased into a 1200 rpm idle (no light). Ran it for about 2 miles at 25 mph and then another 2 miles at 40 mph. I then took it onto the highway and about 1 minute into a 65 mph run the light came on again and stayed on until I parked it about 10 minutes later. So, do I have a bad sensor or something. Any help would be appreciated as it is 120 miles to the nearest mechanic. |