QuestionQUESTION: I have a 1986 420sel.
Lately the car started blowing black smoke from the tail pipe.
The mechanic adjusted the fuel distributor...
The car is still blowing smoke but not as bad as before.
The mechanic also found that there is a vacuum leak to the economy gauge
on the instrument cluster and possibly somewhere else.
He recommends changing the plugs, leads and the EHA valve.
What is your opinion?
Thank you
ANSWER: if you are getting black smoke, you are getting too much fuel, you should adjust the CO to proper specs via the airflow sensor, this is a specific adjustment that must be done with proper equipment. Plugs wont cure the issue.
Common cause is injectors - how many miles on the injectors
leaking injectors, or leaking cold start injector, would cause black smoke
Check timing - is it correct?
how many miles on car? was this a sudden event?
---------- FOLLOW-UP ----------
QUESTION: The car has travelled 220000 km, the black smoke stated rather suddenly.
Prior to this the car would puff a bit of blue smoke after sitting at traffic
lights, the black smoke would sometimes appear on very hard acceleration.
I have noticed that the idle speed seems to be down to about 650 - 700 rpm.
Otherwise the acceleration is smooth, no flat spots.
The fuel distributor and injectors were done 10000 km ago and the idle
control unit was replaced about the same time or a little earlier.
Would a vacuum leak contribute to the problem?
Thank you,
BZ
Answerdid you change out the cold start injector or just the 8? I would check that . A vacuum leak certainly could cause this issue as less air to injectors will cause ECU to dump more fuel to compensate, also your timing will be thrown off ,particularly at idle
