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1986 Erratic Idle and Bog


Vehicle Information: Year: 1986.5; Engine (size, modifications): 5.0l; Total Mileage: 70000; Transmission type: Manual;

I have a 1986.5 928 S 5 speed - I had the car in storage for over a year and forgot to put fuel stabilizer in, but ran the car at idle at least once a month for 10-15 minutes, just to exercise it. It seems that since I took it out of storage, it feels like the fuel injectors are clogged because the idle was erratic and anything from 1100 to 1500 rpm it would bog a little. Ran some primitive tests, MAS air flow checked out okay, needle glowed bright after engine tests, ohms reading through it was okay, checked for vacuum leaks - there are none at throttle body and MAS air flow as well as cross arms intake. Changed water temperature sensor, just out of reflex. Checked throttle position switch - reacted the way it should without any clicks on idle and open throttle. This is what happens: when engine is cold, it purrs like a kitten and runs perfect. 20 minutes later, after it gets warm, after throttling it a couple of times and holding it at several hundred rpms, it wants to choke out unless I pedal it or throttle it slightly to get the idle back. It seems to surge when it falls into this situation and then I take it up, and hold it there and it will surge a little back and forth and then settle down. This happens intermittently. I did not check fuel pressure on rails, regulator or any of that because it was operating perfectly at cold.

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