AX: Stalling & idling problem

Sher_idan · Unread post by **Sher_idan** » 16 Jan 2003, 13:53

Hi all,
My AX ('91H, 1124cc, mk1 'Memphis') has a weird but highly annoying problem that only happens in the morning. After about 5-10 minutes of running, down the bottom of the rev range the car will start jerking and kangarooing, this goes away if revved hard but always comes back. If I let it idle though, the idling gets rougher and rougher, to the point that it stalls. Restart it, and it'll do it again and again, until you turn the engine off completely for 20-30 seconds, and it's fine.
I've also let it 'run through' the rough spot, if left alone it will just about stop doing this and return to normal. Once the problem's been and gone, the car's fine for the rest of the day, this only happens at either first startup or in the mornings.
I've replaced the sparks, HTs, distributor cap & rotor, and the timing belt (drivebelt? cambelt?), to no avail.
If someone has any ideas what's causing this I'd be very grateful, although my local Citroen garage seems to think that it's the carb, and want to perform a strip-down and clean, which I can't really afford right now. I can't also understand how it could be the carb, as it only does it once a day in the mornings, and idles perfectly for the rest of the day.
Any help/ideas gratefully appreciated!
Cheers,
Phil

Unread post by **RichardW** » 16 Jan 2003, 15:29

Phil,
Sounds like you could be suffering from carb icing - if the car has an automatic change over to sucking warm air off the inlet manifold make sure it's working, or force it over to the hot position and see if that cures it.
Richard

Sher_idan · Unread post by **Sher_idan** » 16 Jan 2003, 16:05

Thanks, that's something that one mechanic I spoke to said as well. Do you know where this change over is or how I can find it? I know mine is automatic because the Haynes manual states so, but I don't know where to find it or how to force it over.]
Cheers though, that's made me feel a lot better!
Phil

Unread post by **RichardW** » 16 Jan 2003, 16:54

Phil,
I don't know specifically where it is on the AX, but take a look at the air intake before the filter. There should be a hose running to it from a shroud round the exhaust manifold - this is the hot air intake. Around the area where this joins the 'normal' air intake there should be some sort of device that will change over to hot air. It may be vacuum operated, or just a thermal device - see what it looks like! Check any small vacuum hoses are connected as they should be. I think you can test it by taking it off and applying a lighter (carefully!) to it to see if the flap moves. As a temporary measure you could pull off the hot air duct and just shove it into the normal air intake, and bodge something to hold it in place - this will give you some warm air and some indication if this is the solution to your problems.
Richard

Sher_idan · Unread post by **Sher_idan** » 16 Jan 2003, 20:03

Richard- thank you for your reply, I went and tested the vacuum switch as described in the Haynes manual (disconnect the pipe, blow hard into it, if the flap moves then the vacuum switch is at fault), and it's definitely busted.
Haynes say that on cold start, the flap should move immediately from covering the warm intake to covering the cold intake to help heat the engine, and this isn't happening. The part's on order, £9, will have it tomorrow. W'hey!
Anyway, thanks for your help, wouldn't have thought of that without you- you've saved me a lot of diagnosis cash!
Phil

Unread post by **RichardW** » 16 Jan 2003, 20:12

Let's hope it fixes it - at least if it doesn't you will know it not that (maybe!).
Let us know the outcome!
Richard

Sher_idan · Unread post by **Sher_idan** » 16 Jan 2003, 20:53

Will do mate, maybe it can go in the Solved Problems file that I saw as one of the forum categories for other poor souls that have the same problem. Must say I was worried, it's done 97k and I thought it was the head gasket on the way out.
I'll post tomorrow evening as to what happened, I have to get the complete unit (air filter side of the housing down to the controller unit next to the radiator) but it's only costing nine quid from the local Citroen dealer so that's cool.
Cheers,
Phil

Sher_idan · Unread post by **Sher_idan** » 20 Jan 2003, 15:26

Right, I've fixed the vacuum thing completely, the flap opens and closes on cold/hot start, but the problem's still there. I really thought that this would solve it, and now I'm really annoyed.
Sigh.
Please help!
Phil

Unread post by **RichardW** » 20 Jan 2003, 18:11

Phil,
Bugger, RW has egg on face. At least you know you won't get carb icing now though <img src=icon_smile_big.gif border=0 align=middle>
Ok, does it have a manual or automatic choke? When it does it, have you been driving it, or just letting it idle. Does it ALWAYS do it, and does it always happen in the same place? Is it dark when it happens (you could jump out and look for sparks escaping under the bonnet). How hard do you have to rev it to keep it running? Does it happen regardless of how much fuel is in the tank? What attitude do you park it at - nose up or down? Is a fuel filter fitted - has it been changed recently? <img src=icon_smile_question.gif border=0 align=middle><img src=icon_smile_question.gif border=0 align=middle>
Richard

Sher_idan · Unread post by **Sher_idan** » 20 Jan 2003, 19:17

Richard,
It's a manual choke, someone suggested that it could be the choke butterfly in the carb sticking, something I'm not sure about otherwise it would do it all the time, surely?
When it happens, it does it after I've been driving it, I haven't had a chance to start it in the morning and just let it sit there until the problem occurs again, so I'm not sure about that one. It's a 95% chance of doing it, it hasn't done it a couple of times (thank god) although that's what makes me think it's a cold/weather thing. It doesn't happen in the same place, but at roughly the same time. It will continue happening until I turn the engine off for approx 10-20 seconds, then it's absolutely fine, like it's working something through. As soon as the problem stops, the engine's revving a little high and a lot smoother.
I have to rev it only a little to keep it going, usually just a light touch on the throttle although pulling the choke out won't stop it stalling, it can sometimes make it worse. It's almost always parked level, although a couple of times it's been parked nose up.
And yeah, a fuel filter is fitted (that little white cylindrical thing on the engine compartment bulkhead), that was changed a few months ago. How often do you have to renew them? Maybe it's the wrong one, although Hellfords reckon it's a perfect AX match, looks like it, too.
If someone could solve this for me, I'd be so grateful, I can't have the car doing this on long journeys because I can't pull over all the time, and having it kangaroo down the road is dangerous.
Thanks,
Phil

Sher_idan · Unread post by **Sher_idan** » 21 Jan 2003, 13:32

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Unread post by **RichardW** » 21 Jan 2003, 14:10

Phil,
Not many others takers on this one....
Carb icing was really my best guess, but it seems not to be that. My other ideas were sticking auto choke (now discounted as it's manual) and dirty/wet fuel, but I can't see how this would cause it to only happen in the morning.
Your further descriptions sound like a blocked idle jet - it will run as soon as you open the main venturi, but not on the idle jet. Why would this only happen after first start up? Putting it all together I have just come up with a new idea.... How about your fuel lines are dissolving? Overnight, the petrol dissolves some of the fuel line, and then when this makes its way into the carb (after a few minutes running when the fuel in the carb from overnight has been used up) the gunk gets in and blocks the jet. When you have burnt this fuel, and clean fuel again comes through from the tank it runs OK again. Obscure I know, but new fuel lines are cheap and easy to change.
I had another thought that maybe the thermostat is sticking, and this is causing the engine to overheat a bit, causing the rough running, until the stat opens fully, and normal temp is restored. Very far fetched that one! Stat though is cheap and pretty easy to change.
It does look like your next step is going to have to be dismantling the carb to see what's going on - it's not a difficult job, you just have to treat it carefully, and carefully note how it came apart so you can put it back together again!
Richard

Sher_idan · Unread post by **Sher_idan** » 24 Jan 2003, 00:02

Thanks for that Richard, I'm going to have a look at the stat and fuel lines sometime soon and I'll let you know how it goes.
Did notice this morning though, that the stalling doesn't happen if I turn the engine off for 10-20 seconds *before* it happens, eg at a set of traffic lights. That's a bit strange, no?
Cheers,
Phil

Sher_idan · Unread post by **Sher_idan** » 26 Jan 2003, 13:56

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mbunting · Unread post by **mbunting** » 26 Jan 2003, 14:37

Excuse me for butting in, but I'm taking an interest in all things AX ( as well as Xantia ) now, due to my other half's imminent receipt of a free AX ! ( don't worry about the history, it's a family one ).
Would your age of car have an ECU ? I presume since it's a manual choke, the answer is no. But if the problem goes away when you turn the engine off and back on again before it would have happened, it tends to suggest you're 'resetting' something which given the fact that it happens so quickly, tends to indicate something electrical or electronic rather than a mechanical function.