Black smoke after idle for ten minutes
11-10-2015, 11:53 AM
#1
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Join Date: Mar 2005
Location: Southeastern Massachusetts
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Black smoke after idle for ten minutes
Just wanted to share. My 89S4 was having issues with idle. It would be fine for about 7-10 minutes at first startup. No issues, perfect start and idle. After about ten minutes, idle drops to 500RPM's....goes back to normal RPM'S but would lope and blow out black smoke....really black. Brought her To Metric Motors in Seekonk, MA. Tom is great. Checked the Temp II...tested fine, O2 sensor...tested fine....changed the MAF...no change but it did take longer to start blowing black smoke...Had the Jetronic Computer tested by an unamed world reknown company and it came back no issues bench tested fine.
...WTF....Tom found a similar S4 and took my computer and installed it into that car.....same thing after 15 minutes.....replaced the computer with one from Porsche DME...and success....fixed idle and no issues. So, going forward, just because something tests fine on a bench, the scenario from running for 15 minutes, I assume cannot be replicated. Whether something was heating up in the Jetronic or whatever, real world application cannot be duplicated in a cubicle with a computer.
...WTF....Tom found a similar S4 and took my computer and installed it into that car.....same thing after 15 minutes.....replaced the computer with one from Porsche DME...and success....fixed idle and no issues. So, going forward, just because something tests fine on a bench, the scenario from running for 15 minutes, I assume cannot be replicated. Whether something was heating up in the Jetronic or whatever, real world application cannot be duplicated in a cubicle with a computer.
11-10-2015, 12:02 PM
#2
Team Owner
Thanks for posting the info,
I will add that if your finding smoke of any sort coming from the pipes of an S4 or later,
you should also look under the car to see if the cats are glowing,
If the cats are glowing it would be best to shut off the engine,
and make sure the car is parked away from any buildings.
Fix the issue causing the smoke before further running.
Also its not a good idea to leave the engine running at idle for more than 5 mins as the surrounding area can heat up to very high temperatures,
if the trans cooler lines are leaking then it might cause a fire.
I will add that if your finding smoke of any sort coming from the pipes of an S4 or later,
you should also look under the car to see if the cats are glowing,
If the cats are glowing it would be best to shut off the engine,
and make sure the car is parked away from any buildings.
Fix the issue causing the smoke before further running.
Also its not a good idea to leave the engine running at idle for more than 5 mins as the surrounding area can heat up to very high temperatures,
if the trans cooler lines are leaking then it might cause a fire.