BMW E28 jerks under acceleration and has lost power
Why does my E28 jerk under acceleration or load?
Common causes are an air leak or a mixture that is too lean, and an ignition fault. A broken spark plug wire can cause jerking specifically under load even though idle and light driving are fine. Also check the distributor's ground wire, which may be almost broken.
Which air leaks and vacuum hoses should I check on the E28?
Look at the intake air hose, the accordion-type bellows, which can harden and crack at the ends, and the vacuum hose between the breather and the intake manifold. Also check the vacuum hoses of the distributor and the pressure regulator: hoses connected wrongly after a repair have caused lack of power. The diaphragm of the distributor's vacuum unit may be broken.
What else can rob the E28 of power or make the engine run only at idle?
A broken throttle position sensor can leave the engine running only at idle. A stuck-open idle control valve makes the mixture too rich and costs power. A worn camshaft can also make the engine sluggish. Do not spray water on the air flow meter when pressure washing.