Help me out with this problem which is proving to be extremely stubborn.

Earlier this year I saw my unstable idle problems come back, with some symptoms of the car dying at stop lights when idling in neutral after along drive (it's a manual transmission so it would only happen in neutral). It was an occasional problem I had seen before but thought I had fixed it after cleaning out the ISCV real good.

A few drives after replacing the starter (unrelated problem, the original starter solenoid started clicking when I would try to start) I saw an engine failsafe prog happen when taking the family out for a mother's day hike. The only code was idle speed valve mechanical fault.

Since we are about to sell this car (we just bought an E70 diesel to replace it) I figured, let's fire the parts cannon and make sure we fix the problem rather than let it drag on, replacing parts one by one. So I replaced the ISCV, the MAF (always seems to be a suspect even though it tested fine), and the DISA valve (which had been repaired last year but now had a torn diaphragm). When I took it apart I found a tear in the intake elbow, so I replaced that too. (That was probably the original problem all along, and it had probably torn when reassembling after replacing the starter since I had had it off.) I also replaced the throttle body gasket.

Got it back together for the first time, and it threw idle speed plausibility codes repeatedly, with a high idle, about 1,200 rpm. Figured I hadn't reassembled it right, so I took it all apart and put it back together real careful like. After I put it back together, it seemed to idle high still but solid until I took it for a drive. After I gunned it, the idle started surging from 1,200 to 1,500 rpm repeatedly.

At the advice of this board I took it apart yet again and triple and quadruple checked that I put it back together right. And this time, it idled super solid at about 700 rpm, even on the first half of my test drive, until I gunned it again after which it started surging even more severely from about 1,200 to 2,000 rpm. It went into engine failsafe again and threw the same "idle speed valve mechanical fault" code (no other codes present). Which, the crazy thing is, it drove great for the first half of the test drive, and didn't have the clunkiness associated with a vacuum leak at all. But after it started surging it became clunky again.


Do I have ANY other things to check or try other than buy a smoke tester or pay an indie to smoke test it for me?

Lastly... the throttle body seems to be fine, but when I took it out I notice that it's not fully closed when it is at rest. I can push it fully closed with my finger but it doesn't stay closed. And the other question I had, on the ISCV, the arrow is supposed to point INTO the manifold, right?

Any help is gratefully appreciated as I am at wit's end with this car.

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2003 3.0 5MT Topasblau
Purchased in 2016 and sold in 2024
2012 35d Platingrau