I have been struggling with first an exhaust popping issue even when the engine is warm as well as a low rpm "miss". When started up the car runs rough, missing but it improves as it warms up but never goes away. The exhaust pops, sometimes often, other times seldom so it is not consistent. When warmed up the engine still misses at low rpm and it disappears (smoothes out) around 3000 rpm on harder acceleration. When driving the exhaust will popif there isno load (consistent rpm) and it will disappear as soon as you load (accelerate) or also on deceleration.
I have changed the ignition wires, plugs, cap, rotor, new CO sensor on the exhaust and am about to change the head temperature sensor. The car is a 87 and the exhaust cat has been removed and replaced with a test pipe at some point in its long life.I didn'tthink it would be the exhaust sensorsince it is installed before thecat anyway. It is a strong high mile engine (213k miles) but compression/leak tests etc were excellent.
I have had it to a few specialists without any success so far in solving the problem.
This is a maddening sitution and frustrating enough tohave me looking atselling the car. I have owned several earlier 911's in the pastand never had an unsolvable issue like this. Maybe someone reading this has had a similar issue and can offerdirectionto go for a solution.
Thanks