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From digest.v6.n677 Tue May 20 12:29:25 1997
From: Richard Cartiledge <>
Date: 19 May 97 17:32:21 +0100
Subject: re><E28> L - Jetronic Question/problem

re><E28> L - Jetronic Question/problem "Arthur Manowski" <> wrote...

>I have a problem with my car that i think is related to the fuel injecti=

> Sometimes when I accelerate at low revs (about 2000rpm) the engine feel=

>strained/chocked and not much acceleration occurs. Sometimes it actuall=

>*slows* down. if i ease off the throttle the car seems to accelerate MO=

>than with a larger throttle setting.

This could be one of several things, as always.
  1. AIRFLOW METER When you open the throttle, you are opening the apertu= re of the throotle butterfly, thus allowing more air into the engine. The= airflow meter should measure the airflow and change the pulse-width of t= he injector opening current - (opening duration) this duration is what c= ontrols the mixture and gives the correct amount of fuel for the amount o= f air coming in..

If the airflow meter is faulty, this may give a false impression to the i= njection control unit and thus the mixture may lean out. Over 3500rpm wit= h full throttle (as per throttle position switch), the L-jetronic system = leaves the injectors open continuously, (you may notice a power band star= ts here) this means that the airflow meter is ignored. =20
2. FUEL PRESSURE REGULATOR The fuel pressure at the injectors is desi= gned to remain constant, the amount of fuel injected is controlled soley = by the opening duration. The pressure regulator is located at the end of = the fuel rail and returns excess fuel back to the tank to keep the pressu= re constant. It controls the fuel pressure via a valve which is connected= to a vacuum diagphram. The vacuum hose is connected to the bottom of the= intake manifold. If you think about it, the fuel at the injectors needs = to be about 3.0 bars of pressure, if the intake manifold becomes depressu= rised to say 1.5 bars less than atmospheric pressure, this makes the pres= sure across the injectors 4.5 bar instead of 3.0. If the regulator is fa= ulty, it may be dropping the fuel pressure upon high induction.

3. You dont say which model you have, but you may wish to have the ignit= ion timing checked, and make sure that the vacuum advance and centrifugal= weights are working.

4. Also, the fuel pumps and fuel filter could be inefficient or clogged.

Hope it helps, Richard.

E28 5 series Online Fanzine

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