occasional stalling on a 1.6 i ZX

Hello all, We've just acquired a second ZX, this one for me, to replace the C-15 I used for work (an amazing car in itself, over 370,000 km on it, drives like a gem, though I'm pretty sure the engine was replaced at
some stage). This ZX is from 1992, and has the 1.6 injected engine. It's in overall very good condition, except for this occasional stalling. Here are all the details; I hope someone can point me to solving this.
The stalling started gradually (hardly once on my first drives) and worsened this past week (the previous owner said he felt it just once prior to the sell. I believe him). The stall happens usually around 2500 rpm, and feels as if something cuts off the fuel supply for a split second (which I won't be surprised if that's exactly what's going on). It comes at random, sometimes hardly shows at all, but as it has worsened these past few days, it can come in very short intervals, repetetive, when it can feel like the engine might totally cut out (but doesn't). It usually happens when the engine is cold, or coldish, and I don't think it ever happened when the temp was over 90 degrees. It will stall more in steady state driving (around the 2500 rpm) than in acceleration. If you go over the 2500 mark, the stall will usually go away.
What was done so far by the mechanics was a combo of gas/ignition stuff, beginning with the more basic/simple/cheap: Change of the gas filter, Change of the spark/ignition cables, Cleaning of the main(?) gas injection housing(?) and of the "step/ distribution" motor inside it Change of the ignition distribution/ coil element.
Bottom line, none of the above solved the problem (however, what seems very strange to me is that after some of the above treatments, the stall stopped for a while). Anyone encountered such a thing? Any leads? If it is indeed a gas issue, how does one proceed? Gas pump? Something else along the gas-line to clean and "free"?
Thanks in advance, Ido Yair
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Sounds similar to what I had a few times. Engine just dies (including rev- counter and showing some red lights) for a split second and then goes on again. Happened to me a few times before really cutting out (but able to start it when I got to a standstill) and now, ever so often (maybe once a month) the engine hickups once.
Hey, it's a Citroen. Electrical problems come and go.
I would just clean all electrical connectors in the motorbay.
Maarten
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Maarten Deen :

thanks Maarten, but we covered all the electrical issues. anyways, a lousy update: I went to a injection/carberator specialist, and of course all was normal and they couldn't see the problem. he did say however it's not injection issue cause if so I would have had problem starting the car etc. so the next stage was going to an authorized garage to hook up to the computer for diagnosis. and, what do you know, the car's computer won't "talk" to the outside computer. cool, eh? they said they never encountered such a thing. in the meanwhile my mechanic found a spare fuel pump, he switched pumps, and on one hand, the car hickups a lot less, on the other hand, I got stuck once where it totally died out/ stalled for a few times, and this at idle. eventually this behaviour passed away, but it did appear on the very same day of changing the pumps. are there any units/sensors on the car that could cause such? Thanks in advance Ido
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This sounds very similar to a problem on my diesel Xantia which was cured by replacing the fuel pump relay (after I had replaced a perfectly good fuel pump)!
Cheers Gerald

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Thanks Gerald!

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OK, back from the main authorized garage. This one did manage to connect to the car's computer (their computer was bigger. so size does count). Computer diagnosis: accelerator potentiometer (they used other terms for it to). besides that, from the other signs regarding idling etc., they said it's the step/idle motor that sits inside the injection house. I'm hoping that replacing the potentiometer might cure the idle problems too: the step motor is very expensive (the potentiometer ain't cheap either)..
While I'm at it: what do you fellows have to say about buying such used parts via the net? I was told that the step motor should be new, but can good parts (at low prices) be found via the net or is it to much of a chance and non relevant?
Thanks, Ido
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check this out:
it was the gas pump, and even though I had the pumps changed with a spare one, turns out both were faulty. more interesting, the head-diagnostic-authorized garage was wrong in it's diagnosis, and they didn't even check gas pressure. so who's surprised? it drives great now, and I have aquired piece of mind after ~ 2 months of none. I get too mentally involved with these things. oh, I forgot, I knew they were wrong before the gas check, cause we have another identical ZX, and I switched the accelerator potentiometer, and there was no difference.
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