My car has done about 75K miles. About 2 years ago I noticed the car started to buck and jerk at idle. The rpm fluctuates from about 800 when the engine is hot, down a bit then back up again. Under the hood it sounds as if the engine is loosing power, the picks up again, but not stalling. The idle fluctuation is noticable as a vibration when in my seat. Initially the flucuation got quite bad and there was hesitation and loss of power at accelleration, but after corrective work it improved and is now almost tolerable, but annoying and it has become almost a life's ambition to resolve this problem. At speed the car is responsive and runs smoothly. The problem is present whether engine is hot oe cold. My car is UK spec. and has no Oxygen sensor. LH2.2 injection system, six cylinder engine.

Here's what I have done so far:
1. Changed plugs (Bosch) regapped to 0.6mm, appearance normal.
2. Changed plugs leads (Volvo).
3. Changed distributor cap and rotor arm (big imrovement in responsiveness at speed).
4. Changed oil & oil filter.
5. Changed fuel filter.
6. Replaced air intake & bellow between AMM and throttle body.
7. Cleaned and checked all vacuum hoses, no leak found.
8. Cleaned throttle body (big improvement). Position switch clicks as normal.
9. Replaced oil filler cap O-ring.
10.Replaced ACV valve, didn't fix it although valve was very worn inside.
11.Sprayed water and WD-40 on all manifold seals and injector seals, no change in revs. detected.
12.Put car in to Volvo workshop, they said everything checked out normal, cost me about £200, but problem not fixed. Now I don't trust the Volvo shop.

Please can anyone tell me where else to look. Maybe I am being a perfectionist on this one, but the rev counter tells me something is not right at idle. I am thinking to replace the injector seals, can anyone tell me the Bosch part I need? Any help on this challenge to a resolution would most gratefully received. I feel that if I can resolve this, then I will be on my way to mastering my car (at least for now).

Best Wishes,
KJ
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Kjartan Langskog