The fuel injection system on my missus's 1989 Passat is still playing up.

Starting from cold the revs are all over the place, up and down, the car 
cuts out 3 or 4 times in the first 10 minutes or so.  Settles down when 
warmed up but hardly smooth.

It is the RP 1781cc engine with a single point Bosch FI unit.  My local 
garage man tells me that this is one of the first EFI units fitted and 
they cannot attach their diagnostic equipment to this one.  Anyways.. 
attempting a cheap fix they have swapped the FI unit for a 2nd hand part 
and replaced the 3 sensors (with 3d party units) - to no avail.

They say they are at a loss at what to do next other than for me to try 
a local EFI specialist or (God help us) a VW dealer !

On another group Martin suggested that 99% of EFI problems are sensor 
related and 50% of those are due to dodgy cables.

Is it worth swapping the 3 cables or is it more likely the problem lies 
elsewhere e.g. - ECU ??

Additional info - the crankcase breather pipe is shot and i'll replace 
that tomorrow but I doubt if it will improve anything and I have not 
done owt to the engine recently that could have caused this (e.g. stem 
clean).

The car is not worth a great deal and so I dont think it is worth 
investing big  to fix it - better off using that dosh to put towards 
getting a new motor.

Any ideas gratefully received.

--
JohnB

"JohnB"  wrote in message
news:3mf85cF16b3bbU1@individual.net...

> The fuel injection system on my missus's 1989 Passat is still playing up.
>
> Starting from cold the revs are all over the place, up and down, the car
> cuts out 3 or 4 times in the first 10 minutes or so.  Settles down when
> warmed up but hardly smooth.
>
> It is the RP 1781cc engine with a single point Bosch FI unit.  My local
> garage man tells me that this is one of the first EFI units fitted and
> they cannot attach their diagnostic equipment to this one.  Anyways..
> attempting a cheap fix they have swapped the FI unit for a 2nd hand part
> and replaced the 3 sensors (with 3d party units) - to no avail.
>
> They say they are at a loss at what to do next other than for me to try
> a local EFI specialist or (God help us) a VW dealer !
>
> On another group Martin suggested that 99% of EFI problems are sensor
> related and 50% of those are due to dodgy cables.
>
> Is it worth swapping the 3 cables or is it more likely the problem lies
> elsewhere e.g. - ECU ??
>
> Additional info - the crankcase breather pipe is shot and i'll replace
> that tomorrow but I doubt if it will improve anything and I have not
> done owt to the engine recently that could have caused this (e.g. stem
> clean).
>
> The car is not worth a great deal and so I dont think it is worth
> investing big  to fix it - better off using that dosh to put towards
> getting a new motor.


The early Bosch mono-motronic is hardly rocket science; it presents very few
avenues for fault code reading anyway, so 80% of diagnostic work has to be
done by careful examination and a multi meter.

You can do all this yourself.

First check for vacuum leaks and split intake trunking- this is a firm
favourite on this engine, hoses on the PCV system especially like to split.
Disassembling and cleaning with carb cleaner as you go is the only way.

The throttle butterfly area in the body must be nice and clean, and the
inejector properly ultrasonically cleaned too.

After you've done the above check the CTS and ATS for correct readings- I
always do it at the ECU, as disconnecting and doing it at the sensor may
mask a connector / wiring problem.

CTS - 4v at 10deg c, 0.7v at 80deg c
ATS the same.

Actual values are less important than a smooth transition as temperature
changes...

hope that helps to begin with.

Tim..

"JohnB"  wrote in message
news:3mf85cF16b3bbU1@individual.net...

> The fuel injection system on my missus's 1989 Passat is still playing up.
>
> Starting from cold the revs are all over the place, up and down, the car
> cuts out 3 or 4 times in the first 10 minutes or so.  Settles down when
> warmed up but hardly smooth.
>
> It is the RP 1781cc engine with a single point Bosch FI unit.  My local
> garage man tells me that this is one of the first EFI units fitted and
> they cannot attach their diagnostic equipment to this one.  Anyways..
> attempting a cheap fix they have swapped the FI unit for a 2nd hand part
> and replaced the 3 sensors (with 3d party units) - to no avail.
>
> They say they are at a loss at what to do next other than for me to try
> a local EFI specialist or (God help us) a VW dealer !
>
> On another group Martin suggested that 99% of EFI problems are sensor
> related and 50% of those are due to dodgy cables.
>
> Is it worth swapping the 3 cables or is it more likely the problem lies
> elsewhere e.g. - ECU ??
>
> Additional info - the crankcase breather pipe is shot and i'll replace
> that tomorrow but I doubt if it will improve anything and I have not
> done owt to the engine recently that could have caused this (e.g. stem
> clean).
>
> The car is not worth a great deal and so I dont think it is worth
> investing big  to fix it - better off using that dosh to put towards
> getting a new motor.
>
> Any ideas gratefully received.


Sounds like a problem I had on one of my passats. I took it to various
garages and nobody could diagnose it and suggested I went to the local VW
dealer.
Anyway I took it to the VW garage and just got them to diagnose it and went
and bought the part myself.

It was a squarish type box located on the drivers side bulk head that was
connected to an electrical plug. I'm sure it was called the Air-flow meter.
VW were wanting a few hundred for the part. I got one mail order from a
scrappy from a VW Polo for a few quid.

> > Additional info - the crankcase breather pipe is shot and i'll replace
> > that tomorrow but I doubt if it will improve anything and I have not
> > done owt to the engine recently that could have caused this (e.g. stem
> > clean).
> >
> > The car is not worth a great deal and so I dont think it is worth
> > investing big  to fix it - better off using that dosh to put towards
> > getting a new motor.
> >
> > Any ideas gratefully received.
>
> Sounds like a problem I had on one of my passats. I took it to various
> garages and nobody could diagnose it and suggested I went to the local VW
> dealer.
> Anyway I took it to the VW garage and just got them to diagnose it and
went
> and bought the part myself.
>
> It was a squarish type box located on the drivers side bulk head that was
> connected to an electrical plug. I'm sure it was called the Air-flow
meter.
> VW were wanting a few hundred for the part. I got one mail order from a
> scrappy from a VW Polo for a few quid.


I've just looked at a picture of an air-flow-meter and it wasn't that.
Sorry. It was called an Air-"Something". It was a wee box and sat on the
bulk head with a couple of wires going in to it. If I unplugged it the car
actually ran better but still not good enough.

It was around 10 years ago so my memory is hazy to say the least.