Saxo 1.1 Engine Management Issue

[rob2cv]

Hello there,

I have joined the forum after lurking for a while in the hope of someone here being able to diagnose an intermittent fault with my W reg, 1.1, Saxo that was recently purchased for my wife to drive. I have tried searching the forums for an answer without any luck.

The fault seems very strange to me, although as a 2CV driver I am not used to cars with electronic ignition or fuel injection(!)

The car regularly kangaroos, stopping and then suddenly starting again in a very violent fashion...It's as though the ignition switch is being turned on and off when you are driving. It never lasts very long but it is very disconcerting when it does happen. (Usually when pulling out into traffic!)

I can happen from cold, or after driving for some time. It can happen 5 times a day or just once a month. It has happened when the fuel is low and when the tank is full, at low speed, when stationary or at higher speeds.

On closer analysis the symptoms are very specific. I have caught it a couple of times from cold before setting off. If one presses the accelerator pedal very gently the revs will rise steadily to 2000 revs. At exactly this point the engine seems to cut out until the revs drop back down to tick-over. Keeping the accelerator pedal pressed the revs will rise steadily again until 2000 revs are reached and the cut out back to tick over. The effect is one of rhythmically blipping the throttle although the pedal stays gently pressed. There is no EM warning light on the dash when this happens. If the ignition is switched off and the car is restarted it is fine, or if you rev the engine really hard (in frustration) then it seems to clear the fault.

Also, it will not fire up or tick over from cold without pressing the accelerator. I have renewed the EM coolant temperature sensor without any change in this symptom.

The engine management system is Bosch MA3.1

My wife now refuses to drive the car and the fault is spoiling an otherwise decent little runabout.

Does anyone have any ideas, or has experienced this same fault?

Thank you, in anticipation, for your help.

Rob

[Chris570]

Can you confirm that the inlet manifold is plastic on it and not metal. (the difference is Multi-Point injection and Single Point.)

i'm thinking map sensor.

Does the engine management light come on when the ignition is on but without the engine running?

[rob2cv]

Hi Chris,

Thanks for the quick reply!

Yes, the EM warning light does come on with the ignition switch but goes out shortly after the engine fires up.

The inlet manifold is cast alloy, but if I had to guess then I'd say that it has single point injection looking at it. I don't know what the MAP sensor is?

Here a snap of the engine bay and one of the label on the top of the ECU



Rob

[Chris570]

Thats a single point one there.

an interesting problem you've got there (although i doubt you'll agree)

Would it be fair to say its a particular "spot" on the throttle that causes this?

if so then throttle potentiometer (i had this on my AX once although not as bad)

logically any fault that is as bad as this should put the engine management light on or at least log some kind of fault.

Is this something you can reproduce at will?

[KevMayer]

We have a W reg Saxo 1.1 in the family. It's my daughter's and I drive it from time to time. It's a great little car.

We had a problem very similar to yours a few years ago, when I was at the bottom of the learning 'Citroen/cars in general' curve. I took it to a Citroen specialist and they changed the engine management ECU and it's been fine since.

The Citroen specialist said we'd toasted the ECU when we bump started the car because of a flat battery. ECUs don't like bump starts apparently.

With the same problem now i'd start by disconnecting the battery for an hour to see if that resets anything in the ECU.

Then, if still faulty, I'd take the air box off and strip down and clean all the air intake system. You may have an intermittant air leak problem which could be a faulty idle valve (the one which controls the mixture at tick over. I think that's what it's called).

If you could risk £200 ish then a Citroen specialist can probably diagnose the fault and sort it out.

The Saxo is a good little car and worth looking after.

[rob2cv]

Hi Chris,

The problem occurs at exactly 2000 revs on the tachometer and not at a particular throttle position. I cannot replicate it at will.

Hi Kev,

In the winter I had to take the battery off to charge it up after a cold snap. The fault was still there afterwards.

Rob

[mooseshaver]

I had a problem with a Saxo that was similar but not quite the same. The car seemed lumpy some mornings, would not run correctly, would stall when accelerator pressed.
It was somethignt o do the the leads that go into the spark plugs as one of them gave me a shock when I pressed them down in turn.
Could it be this?

I did not pass that info onto the dealer who had not been able to fix the fault in the three years I had it as I was handing it back to Citroen and picking up a C3 that day.

[radders567]

Hi all I'm new to the forum.

Appologies for re invigoating an old thread.

I have exactly the same problem as ROB2CV in the first post. Rob did you manage to solve the problem ?. All - has anyone else experienced this problem ?

So far I have changed:
Plugs
Leads
ICV
removed and cleaned injector
throttle body has been cleaned with carb cleaning spray
Set tappets
Checked for air leaks
exhaust is in as new condition
air filter is in as new condition

I am running out of idea's - possibly Crank sensor or lambda senor. I am not entirley sure how to check these and what values to expect.

Any thought's

[rob2cv]

Hi radders567,

I'm afraid the fault is still there! Let me know if you get yours sorted out.
Good luck,
Rob

[radders567]

Rob I removed and cleaned the connector on the side of the throttle body. The one that goes to the orange / brown throttle position sensor on the side i then gave the connector a squirt of wd40 and the unit itself. So far today I have not had the problem return. Keeping my fingers crossed.

[radders567]

Just a quick update.
I have now renewed the Lambda sensor which made it a little bit better. I then removed the manifold and renewed all the gaskets. I also removed the throttle position sensor and cleaned it inside with WD40 then dried it of with clean kitchen paper. All seems well now. The car idles properly and drives smoothly.