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Re: FI rough idle



> I have a weird problem with my FI:
> - the engine starts up immediately, even after one night rest;
> - however, it idles rough; I finally learnt that of the of the cylinders
>   does not work at all (random, sometimes #4, sometimes #2, sometimes...),
>   even though they all would work properly at higher rpm;
> - also, at idle, if I let to much air by adjusting the screw on the 
>   air intake case, I got only #3 and #4 running!

Using a good voltmeter, measure the battery voltage at fast idle 
after going for a short drive (to get the battery up to an 
equilibrium charged state.)  The voltage should be 14.1-14.4 V.  If 
it is less than 13.5, replace the voltage regulator.  Low system 
voltage will make the FI run rich and can have symptoms like you 
describe.

> I suspected that the injectors clogged. I poured an aditive in the gas
> tank. No change. Fuel pressure is 2.1 bars.
> I mounted brand new injectors ( BOSCH 0 280 150 105). No change.

The correct injectors for our cars are 0 280 150 007.  The ones 
above are used on Alfas, Renauts, Opels, Porsche 912Es, and Jaguars.

> I re-re-rechecked the wiring, suspecting some bad grounds. All was OK.
> Throttle switch and pressure sensor OK too.

It is common to have bad connections to replacement injectors
because the material thickness of the metal used to make the pins in
the replacement injectors is smaller (by a few thousandths of an
inch) than the OEs.  This can be fixed by CAREFULLY removing the
female pins from their plastic holders and CAREFULLY squeezing them
a bit until they are a snug fit on the injector pins.

If you go gonzo at this you will just ruin your harness, so be warned 
that this a place to work slowly and carefully.

Jim
-
*******************************
Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA
*******************************


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