Good thing to check. Air as a percentage of fuel could be higher at low revolutions. Or the issues it produces more apparent then.


Also especially since the car has the 616 engine the fuel system should be checked out well. Not expensive to do either other than the injectors being checked for condition usually.


The car is thirty five years old and in all too many cases it has been years since anything much was checked. If anything on a lot of them. The last owner may not have even done a valve clearance check. They should at least be checked every fifteen thousand miles. This also could be a portion or contributor to your current issues.


These engines do not require a lot of maintenance. Yet none done over a very long time will have consequences. You may as well check the timing chain for excessive stretching as well. Not doing this can cost you the engine. Also the condition of the oil cooler hoses. As the engine can be easily destroyed if they fail.


Generally paid for service is not a practical reality with these old cars and many other brands today. So the owner and perhaps a friend do it or it does not usually get done.


At least with the assistance of this very useful site. You can do a lot yourself. To me just having the proper fuel pressure available to the injection pump is important on the 616 engines. Air free of course as well.


I freely admit on more complex cars. I have engaged in a general tune up of all the engine systems. Basically checking them and repairing any that were found less than normal.


Either I found the problem in many cases or the problem was gone along the way. Or I found a good indicator of what it may be. At least I then knew what it was not. On a neglected very old car you can have a lot of accumulated minor problems.