1995 A8 Misfire with CAT light
10-08-2013, 04:33 PM
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1995 A8 Misfire with CAT light
Hi - I am a new user and a new Audi owner. I just bought a 1995 A8 in Australia.
After a few weeks of owning it - it has started to develop a shaking which is now continuous making it almost undriveable. I was hoping to do a bit of diagnosis myself (with the benefit and expertise of these forums of course!) before having to resort to a mechanic as I don't know of any local mechanic who might be good at this age of Audi.
The problem started with the CAT light on the dash flashing - usually only 3 or 4 times and with no other issue. After three or four flashes it would go away and the car would be fine for a while. After 3 or 4 days of this the CAT flashing become a bit more frequent and was accompanied by a shaking / shuddering - but again this only lasted 10 seconds or so then cleared up and the car drove fine again.
Today though when I started it and drove for a few minutes, the CAT light started flashing and the car started shuddering violently with a loss of most power. It stalled when trying to drive off. I restarted it and managed to drive it the few kilometres home but it was shaking continuously, the CAT light flashed continuously (with a regular rhythm) and was very low on power. It feels like it is missing several cylinders (maybe a whole bank?). The shaking is worst at idle, and clears up a bit at higher revs although the power is still absent. Sitting idling in drive gets a lurching / shaking - putting the auto in Neutral or Park is better but still shaky as the car drives off.
Any ideas on where to start? I have read about ignition amplifiers potentially causing this and was going to test them, is this just a case of testing continuity from one side to the other? Any other suggestions? Prior to this the car was running well with good power etc. I guess the CAT light is to do with the catalytic converter, how do I check if there are issues with the catalytic converters and could they have these symptoms?
Any advice or suggestions would be much appreciated!
After a few weeks of owning it - it has started to develop a shaking which is now continuous making it almost undriveable. I was hoping to do a bit of diagnosis myself (with the benefit and expertise of these forums of course!) before having to resort to a mechanic as I don't know of any local mechanic who might be good at this age of Audi.
The problem started with the CAT light on the dash flashing - usually only 3 or 4 times and with no other issue. After three or four flashes it would go away and the car would be fine for a while. After 3 or 4 days of this the CAT flashing become a bit more frequent and was accompanied by a shaking / shuddering - but again this only lasted 10 seconds or so then cleared up and the car drove fine again.
Today though when I started it and drove for a few minutes, the CAT light started flashing and the car started shuddering violently with a loss of most power. It stalled when trying to drive off. I restarted it and managed to drive it the few kilometres home but it was shaking continuously, the CAT light flashed continuously (with a regular rhythm) and was very low on power. It feels like it is missing several cylinders (maybe a whole bank?). The shaking is worst at idle, and clears up a bit at higher revs although the power is still absent. Sitting idling in drive gets a lurching / shaking - putting the auto in Neutral or Park is better but still shaky as the car drives off.
Any ideas on where to start? I have read about ignition amplifiers potentially causing this and was going to test them, is this just a case of testing continuity from one side to the other? Any other suggestions? Prior to this the car was running well with good power etc. I guess the CAT light is to do with the catalytic converter, how do I check if there are issues with the catalytic converters and could they have these symptoms?
Any advice or suggestions would be much appreciated!
10-09-2013, 10:26 PM
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An update on this - I got a mechanic to check the codes and it had a multitude of them which put it in "Limp Home" mode which caused the problems with running on 4 cylinders. Once the codes were cleared the car is running fine again. I plan to drive it now till the next code come up and check them before it has time to run too badly and flood the computer with errors again. Will advise once I know what the specific code is that is causing the problem.
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