Citroen AX 1.1 Echo Plus

[jamesnoble]

I have had a small thermal incident on our lovely AX 1.1 Echo Plus. The 2 wires to this part on the Magnet Morelli single-point injection housing/throttle body shorted out. Whatever this part was it is now a charred mess! Strangely no fuse was blown!

So now the questions. What is this part and what did it do? The car runs fine still but it is now very difficult to start from cold... So I guess it's something to do with the cold start system.
Secondly can I buy this part on its own or do I have to buy a whole new throttle body?

Any help gratefully received!

[CitroJim]

I was initially thinking it was the idle stepper motor but I'm now not so sure as both my AX and my Saxo have the Bosch single-point TB and whilst they look similar they are very different...

Generally parts can be replaced but are hard to obtain now. You'd be best off hunting down one from a scrapper... Be sure to make certain it's an MM as the Bosch version is not interchangeable...

[wheeler]

The bit right above the knuckle looks like the stepper motor.
If I remember right do these throttle bodies not have a little heater element in them to stop icing up?

[jamesnoble]

Thank you both of you. The area I'm pointing to is thge bid that combusted! I wondered if it was a heater element; there are only two wires...

Anyone got a wiring diagram for the MM system?

[wheeler]

Whats the year & engine code & I’ll have a look on autodata.

[CitroJim]

If I remember right do these throttle bodies not have a little heater element in them to stop icing up?

They do indeed. My Bosch variety certainly does...

I disconnected mine once during some fault-finding and it made little or no noticeable difference. Maybe in this current cold it may...

[jamesnoble]

Whats the year & engine code & I’ll have a look on autodata.

The reg is L386SHU
I'm not sure where to find the engine code but here is the RP number and the chassis plate

[wheeler]

Just had a look on autodata, no wiring diagrams on this car im afraid.

[jamesnoble]

Just had a look on autodata, no wiring diagrams on this car im afraid.

Thanks anyway; pretty sure what's gone up in smoke is the heater element but I think I'm looking at a replacement throttle body

[xantia_v6]

It is very likely that the fried part is a de-icing heater element, which is there to prevent the throttle butterfly from icing up under specific atmospheric conditions (ambient a few degrees above freezing with humidity near 100%). It does not have any effect on cold starting, it is not powerful enough to warm anything within a few seconds. There is probably little benefit in replacing it.

You cold starting issue is likely to be elsewhere, I would suggest starting with the easy things like checking the condition of the ignition HT components. I don't know if this injection system has any components which are specifically used for cold starting.

[CitroJim]

You cold starting issue is likely to be elsewhere

My experience, being the owner of two TU engined vehicles with the single-point throttle body injection is that they both take a bit of spin on the starter before they start from cold... They do not, by any stretch of the imagination, start instantly.

On my Saxo I spent a lot of time investigating this, including fitting a new fuel pump and checking the throttle body heating system (the element of which you think you've cooked) and found it made no appreciable difference one way or another to cold starting... Not that it was tremendously cold when I did my tests.

I came to the conclusion that less than instant starting from cold was a feature and not a problem... Neither of mine have ever failed to start...

Just how hard is yours to start?

[jamesnoble]

This saga has continued for some time. The car has been running badly and idling appallingly. This all started after the deicing heating element in the throttle body burnt out.

After much head scratching we wired a bulb in place of the heating element and normal running was restored! However it still has the occasional blip. It looks like the ECU needs to know that the heating element is there!

So I'm back to my quest to find a replacement deicing heating element or indeed a whole throttle body. In my testing we have established that the throttle potentiometer and the stepper motor are all functioning correctly.

So if anyone has a new or second-hand Weber solex throttle body for the magneti marelli ECU equipped 1.1 TU engine, please please please get in touch

[CitroJim]

James, that's really interesting that the ECU needs to 'see' the heater present

The occasional 'blip' may be caused by the throttle pot. It's not replaceable but with huge care it can be removed from the throttle body and very gently cleaned...

I've had this issue on both my Saxo and AX...

[jamesnoble]

Thanks Jim. It has been removed and cleaned. I am convinced that the occasional blip is related to the heating element as it puts the engine management light on momentarily when it does the blip.

[CitroJim]

Thanks Jim. It has been removed and cleaned. I am convinced that the occasional blip is related to the heating element as it puts the engine management light on momentarily when it does the blip.

That rules out the throttle pot then as I've never seen the engine management light come on when the blips have happened on mine...

I have the remains of a throttle body but it's a Bosch... Not sure if the heaters are the same?