Astra ECU, cat. problems

Here's where I try not to write a whole book ...and switch into Yoda
speak !

Dads' 1996 Astra Estate 1.6 16v CDX just failed its' MOT, (by a VX dealer),
on emissions,
VX said it may be just a sensor, (I'm guessing they meant the exhaust
manifold Lambda/oxygen sensor), and so we left the car there. 2 hours
after we got home they phoned to say it was not the Lambda and that the cat.
had failed. On the last MOT
just after he bought the car, it failed on emissions and had to have a new
cat. !
....collected car and brought it home we did

So I started to investigate, trawled around web and found
http://www.topbuzz.co.uk/info/fault_codes/fault_codes.htm#gm and the OBDII
site but, (couldn't find anything on OBDII!).
....discovered that the ECU lamp in the driver instrument panel had been
removed, (so I put a new lamp in it).
....bit puzzled as to Dad's car having a 16 pin ALDL connector on the fuse
panel, and http://www.topbuzz.co.uk indicating that it would be a Simtec
56.5 system which reports 4 digit codes, yet when I stuck the paperclip in
it, and switched on the ignition, it blinked out "2 digit" codes -> 12, 47,
85, 84, 92, 93, and 19
....am guessing that it's GM-Multec-CFi ECU, (process of elimination / none
of the others have a code 47?). I can't see the engine no. on the engine
block - and last night I spent ages taking out the trim on the passenger
side footwell/kick panel just to discover two big electrical connectors and
no ECU ! ...well I thought the Haynes manual "ECU is under the kick panel on
the right side of the car" meant as one stands looking at the car -
obviously it meant as one sits in it ? <blush>

....anyway, I've bought a new front pipe, and cat. section, and gaskets, and
in a couple of days when my old boss has a free ramp, I'll fit them. He
also said that he can plug onto the 16 pin ALDL connector with his whopping
big diagnostics equipment in his workshop. So perhaps he'll help me sort it
out. Though, he's doing a ful service on another ramp, so I'll have to try
and not be a nuisance.
My question, or concern if you like is what is causing these cat's to fail
prematurely on Dads' car ?
The nearest thing I could come up with, is to do with the error codes & ECU
light permanently on. i.e. I read somewhere that if it stays on for more
than 30 seconds, the ECU switches to an emergency program to keep the engine
running and therefore "engine management" and "emissions control" etc. are
not being used. Does this perhaps mean that a fuel rich exhaust gas could
be poisoning the catalytic converter ? ...well that's my best theory so
far.

Any pointers gratefully accepted
TIA
....regards, Richard

 

well i'd certainly go with limp home mode eventually kill a cat.
i've seen that before but ofcourse its why its going into limp home mode?
i'd do the work and go from there, should give you some codes to look at.

the only other thing that springs to mind is a hole in the manifold letting
in air or poor manifold gasket where muppets have sheared the studs off?
found that to be the case on a 1997 sintra with the same engine,
pig to change on a sintra mind you!

mike

 

Thanks MikeFNB, ...much appreciated.

regards, Richard

 

Overfilling with oil might cause early cat failure.

Also, check the auxillary air pump & the associated valve, these are
supposed to protect the cat by supplying extra air on startup
(counteracts the rich fuel mixture). Usually this pump only runs for 1
minute or so after startup.