BX GTi runing very rich

Our most popular forum is for Citroën problems, discussions and chat.
Specialising in AX, BX, ZX, Xantia,C5, Xsara, Saxo and XM. CX, 2cv & Berlingo, all are welcome.NOT for selling cars/parts!

Moderator: RichardW

martinwiseman
Posts: 7
Joined: 13 May 2002, 17:06
Location: United Kingdom
My Cars:

BX GTi runing very rich

Postby martinwiseman » 25 Jun 2002, 17:32

I've reached desperation point with my GTi (1991 H reg - with Motronic MP3.1 engine management system).
It's been a bit down on fuel economy for some time, but in the last couple of weeks it has got really bad and will no longer run at idle.
The symptoms are that it starts fine and as long as you immediately rev it up to over 2000rpm, it continues to run. It can even be driven (although it's a bit under powered), but if the revs drop below 2000 it runs very rough and below 1500 it eventually cuts out. The cause of this appears to be that the spark plugs are rapidly sooting up - i.e. it is running very rich. In the last week it has used an entire tank of petrol in 200 miles.
I've checked the sensors - air and coolant temperature sensors are giving sensible values, the throttle potentiometer works fine, the CO potentiometer works fine (although it is at it's minimum value) and the MAP sensor (internal to the ECU) doesn't have an air leak. I've tried replacing the pipe between the manifold and the MAP sensor in case that was leaking - makes no difference. The pressure in the fuel rail is 3.5bar absolute which I think is correct(I am assuming that the 2.5bar rating on the pressure regulator is gauge pressure rather than absolute pressure). With the fuel rail removed from the vehicle, the injectors all give a reasonable spray pattern when energised and don't leak any fuel when not energised. Removing the air filter doesn't make any difference.
I'm going to borrow an oscilloscope from work this evening to look at the injection pulses but I'm not sure that will actually tell me anything new because I already know it is injecting too much fuel.
So, can anyone suggest something that I've missed.
Alternatively, is there anyone in the Cambridge area with an H reg BX GTi that would let me try my ECU in their car because that would seem to be the only component I haven't tested.
Thanks,
Martin Wiseman
0 x

Jon
x 2

Postby Jon » 25 Jun 2002, 18:12

Martin,
Read your post very carefully and also spoke to a colleague here about this interesting case of over fuelling.
Its odd because the obvious causes (sensors) seem to check out OK. I'd certainly try a "known good" ECU if you can. Before you do so, try this. Have a look at the carbon track on the air vane on the airflow meter. It may be stuck or dirty, causing an incorrect air to fuel ratio. Mark the position of the airvane flap, then turn 2 clicks anti clockwise. See if this makes a difference. If no difference, return to your original (marked) position and move 2 clicks clockwise.
This may help.
You may ultimately be looking fitting a better air flow meter if the above does not solve the problem!!
Good luck!
Jon
Jon Wood
IT Supervisor
GSF t/as Andyspares
0 x

martinwiseman
Posts: 7
Joined: 13 May 2002, 17:06
Location: United Kingdom
My Cars:

Postby martinwiseman » 25 Jun 2002, 19:27

Jon,
<BLOCKQUOTE id=quote><font size=1 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>
I'd certainly try a "known good" ECU if you can. Before you do so, try this. Have a look at the carbon track on the air vane on the airflow meter. It may be stuck or dirty, causing an incorrect air to fuel ratio.
<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>
Thanks for the suggestion, unfortunatly you are thinking of the older version of the GTi. I have the version with a Motronic MP3.1 ECU (produced from 1991 onwards) which measures manifold air pressure (via a pressure sensor that is internal to the ECU) instead of using an air flow meter.
Martin.
0 x

NiSk
Posts: 1435
Joined: 24 Jan 2002, 21:11
Location: Sweden
My Cars:

Postby NiSk » 25 Jun 2002, 19:49

Hi Martin,
Does the Motronic not have an air mass sensor? Your fault certainly sounds like duff air mass sensor.
//NiSk
0 x

cavguyuk
Posts: 5
Joined: 11 Dec 2004, 21:53
Location:
My Cars:

Postby cavguyuk » 11 Dec 2004, 21:59

did you ever sort this mate!? i have the exact same thing!
0 x

alan s
RIP 2010
Posts: 2624
Joined: 26 Jan 2001, 16:53
Location: Australia
My Cars:
x 4

Postby alan s » 12 Dec 2004, 01:52

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by cavguyuk</i>

did you ever sort this mate!? i have the exact same thing!
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
He hasn't been on this forum since June 2002 according to his profile so I don't like your chances of a reply.
Alan S
0 x


Return to “Citroën”

Who is online

Users browsing this forum: Bing [Bot], Google [Bot] and 14 guests