Hello-Need to ask u a question. My son has a 87 Saab turbo. Dist. has been rebuilt most everythig replaced-no luck. When cold runs and idles great-but when warms up goes to 3000 rpm down to 0 then erratic until stalls--Will start back up but runs rough refecting in tach bounce. What does he seem eo have overlooked other than a mechanic-Thanks
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Yes would like a response-Thanks
Hello and thanks for using Just Answer, sounds like possibly air leakage of some sorts, possibly around an intake runner where intake attaches to cylinder head. While car is running "poorly", spray some combustible aerosal (brake cleaner,carb cleaner) around where intake meets the head. If that makes idle jump you have an intake leak. When aluminum heats up it expands which is opening up leak, it gets cold and shrinks and seals up. The professional way to diagnose is with a smoke machine, but they're a couple thousand bucks. Try the spray can trick. Good luck, hope this helps, if it does PLEASE hit ACCEPT.
Have tried all of these steps no difference
On intake near throttle body, there's an idle motor which controls idling RPM's try banging on it with screwdriver handle(don't beat it with a hammer) and see if it levels out, here's a picture so you know what it looks like, also check the hoses going to it for leakage. Good luck, hope this helps, if it does PLEASE hit ACCEPT.
Over 15 years Saab experience
The idle motor has been replaced earlier with no improvement-going to try a new coil-sound reasonable?
They're not super common to go bad, bad it sounds your getting desperate, maybe during poor running, try unplugging the Mass Air flow sensor and see if it runs any better.