There is no problem to start the engine, but right after start up the RPM is fluctuating between 500 and 1000 for a minute or two. When I try to drive it it behaves as if the fuel was cutting off. It does not stall but lacks power, same as if the tank was empty and running on fumes. After few minutes of “no power symptoms” the car drives O.K. Yes, I have changed check valve and fuel filter, but it didn’t solve it. What is the next suspect? The car just turned 300K km. It is 740 Turbo 1991.
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'91 740 turbo SW, '92 940 turbo, '94 940 Regina SW (PL)

Remove and clean the IAC with brake cleaner. Spray it out until it frees up and starts flopping around. Turbos gum up the valves with oil vapors. I believe yours is a "two wire" type and can't be taken apart and cleaned out like the older "three wire" ones.

To solve this problem I’m considering swapping ’91 740T ECU ...563 with spare at hand ...937 which can be found in ’92 940T and see if it is the ECU that is acting here. My question is: are they compatible? The only difference I see is that my ’92 940T with ...937 does not have cold start injector which is present in ’91 740T that I have problem with. Did anybody do such a swap with good results? I don’t want to fry good spare.
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'91 740 turbo SW, '92 940 turbo, '94 940 Regina SW (PL)

I'm not too familiar with Turbo cars, but it seems that the next suspect would be the cold start injector. But I don't know if the turbo system uses one. It is off the fuel rail between the #3 and #4 cylinders. Check and let us know.
el Raidman

The OBD shows 1-1-1, should I get 3-2-1 with faulty injector?
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'91 740 turbo SW, '92 940 turbo, '94 940 Regina SW (PL)