Just took delivery on a 92 512 TR The car is beautiful. EXCEPT It bucks and jerks just after a few minutes of starting the car. The dashboard warning lights that tell you to slow down because cylinders 1-6 or 7-12 are not working correctly keep coming on? I've relaced the O2 sensors in the catalytic convertors today, but nothing has changed. Anybody have any ideas? Help???
I think you're already looking in the right area (something is wrong when it tries to run closed-loop after warming-up using the O2 sensor output signal), but just to reconfirm that you might try just unplugging the O2 sensors when warm and see if things smooth out somewhat. Usually these O2 controlled injection system are designed smart enough such that when it can determine that no O2 signal is present it will default back into the "dumber" cold-running mode. Did the car previously run well warm? You don't give much background so you might reverify that the 1/6 O2 sensor is connected to the 1/6 injection control unit, and likewise for the 7/12 side -- did you just put a new exhaust system on it where who's-who might be mixed-up? I know that putting a Tubi on my TR required moving the O2 sensors around physically to keep things right. Getting exhaust overheating indications on both banks is a little unusual based on the split injection architecture...
The O2 sensors only modify the base line setting, unplugging them does not return it to a cold operating condition it allows it to return to an un modified state. But you are correct, unplugging them will eliminate them as a cause. If hooked up backwards it will be a disaster, but I dont think that the wires are long enough on a 512TR to do that. The ck engine lights (if those are the ones that came on) indicate that something has been registered in the computer memory and can be accessed easily.That should be done before you spend any more money throwing parts at it.
I was referring to the cold operating situation as an "unmodified" (open-loop) state so I don't understand your distinction... PS shouldn't a Moderator move this thread into the "Classic" section?
There are a host of differences in a cold versus hot operating condition. There many inputs to the motronics several of which are temp related. The o2's are not one of them in the strictest sense. The The o2's go off line (open loop) in a couple of situations not necessarily temp related and their going to open loop does not return the motor to cold operating mode. In any event I made the statement to bring a little more precise information into the conversation, not just in an effort to correct you.
I'm sorry that I forgot to mention the most important thing. If the lights that are coming on are the slow down lights that is an indication of the catalytic converters overheating and the motor should not be allowed to run very long in that situation. The cats can get so hot they can set fire to the car, (I've seen it happen) and even on a much less severe overheat the cats themselves can be destroyed, Very $$$$. At this point it may be less expensive to get it to a shop experienced with those cars.
Steve: I bought the car from a dealer in PA. And he told me he drove it a week before delivery and thing s were perfect. (yeah right) The service records indicate a full 30K service was done a thousand miles ago (car has 29K) at ALGAR in Philadelphia. Anyhow, It never has run correctly since the day I got it last week. Now the dealer will take it back and have Algar look it over again, but I though if it was something easy I could do it here in New York. After all I want to drive the car. But that does not seem to be a reality, now. I bought new O2 sensors and installed them. With no change at all? And this morning I unplugged the O2 sesnors completley. Although the car seemed to idle better, it was not searching for an idle speed, as soon as I drove the damn thing it started backfiring etc... Now the guys at Miller Motor Cars, and Algar tell me that I might have to change the "PROBES" also? Paul
A long shot but have you tried disconnecting the battery for a minute and then retrying? It resets the system and works on my 512TR for a few months when a yellow light comes on for a particular bank. Your problem sounds different but its worth a shot. By the way , disconnect the battery cable not just turning the switch off.
I have a 92 TR and i have had the same problems. It could be a number of different things my problem was bad spark plugs and i had a burnt valve. good luck with finding the problem.
how can replacing CATS affect the cold start problems? I don't understand. Cats aren't even in the loop when engine is cold. < And this morning I unplugged the O2 sesnors completley. Although the car seemed to idle better, it was not searching for an idle speed, as soon as I drove the damn thing it started backfiring etc... > So when you didconnected the O2, you had the above quote, well then your problem has nothing to with Cats or O2s then. Once you have disconnected the O2 sensors, the motronics will stop using them to calculate fuel metering. It will rely on your TPS and Hotwire AF. Also check your FPRs vacuum line for unmetered fuel going back into the inlet manifold.
