Re: k-jet Idling Problems

[Kalves Tom <k140119@xxxxxxxxxxxxxxxxxx>]

> Hi
> 
> I really appreciate if someone can give me some information that will
> enable me solve a problem I have with the engine idling of
> my E28, 520I, Euro K-Jetronic.
> 
> The overall situation is as follows:
> 
> On cold start the engine does not idle at 1500 rpm but stays at below
> 900 and occasionally stalls if not assisted by  pressing the
> accellerator. When the engine is warm, idling will rise automatically to
> 1500, instead
> of 950 RPM.
> 
> Although I will be able at times to reduce it to 950 RPM by engaging on
> high gear and disengaging, it will after a few seconds rise again to
> 1500.
> 
> When driving behind traffic, and hence  the temperature rises above
> normal, the engine idles erratically and eventually stalls.
> 
> Starting a warm engine that has been shut down for about half an hour is
> difficult as idling will be erratic
> and engine will stall.
> 
> Thanks Tony
> 
> Wishing you all a merry Christmas
> 
> 

Hi Tony,

First you have to understand that a lot of things could cause these
symptons but let assume that the basic things have been taken care of,
i.e. high pressure fuel filter, spark plugs, airfilter, valve
adjustment etc..

Next, lets also assume that your mechanical water heated choke is
working and your motor still has some mileage on it (good pressure in
sylinders and no huge clouds of blue smoke). Now, we are getting into
business. I think you have a lean mixture.

Check EVERY hose on that motor for air leaks - especially bypass hose
that come to the manifold and intake boot after the air flow meter. Try
adjusting the idle from the screw where the bypass hose is attached to
the manifold. Also screw the mixture hex on the air meter all the way in
(rich) and then about 2 round out (more lean). Note that this mixture
will have effect only from idle to mid range, when revs are high or you
pressing the pedel a lot, the air flow meter is fully (or near) open and
this small bypass valve has no effect on mixture. Try playing around
these two adjustments to get it right.

Also, check the fuel pressuse or pressure regulator (before any
adjustments!). I do not think that it is the cold fuel valve or
thermotime switch that controls it but with the symptons you described I
cannot be sure. If the consumption is ok and the engine starts sharply
when it is cold, then this is probably working ok.

I would gues that maybe your machanical choke is not working (moving) 
as much as it should (bad cold idling) and the idle is set too high for a
warn engine (idle screw). But then it dies in traffic from no fuel(?) 
(well I would also!). It could be filter(s), bump, pressure regulator or 
broken hose.

Good luck and happy New Year 1999!


- - Tom Kalves
'82 520i
'86 M535i

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