ZX stepper motor disconnected

SuperSerdo · Post by **SuperSerdo** » 12 Aug 2003, 14:45

Hi all,
Lately my ZX 1.6i has starting problems. It starts up fine, but right after it stalls, unless I keep it alive by accelerating a little bit, until the injection check lamp goes off from the dashboard (2-3 secs), then it idles fine on its own. In citroen they told me I had to change the stepper motor, but didn't feel like spending the 120€ right off, so I took the stepper motor off and cleaned it, still no good. To me it looks like it works though, as it would move up and down when operating the ignition key, being the motor off the engine and connected, and it idles perfect, only the startup is the problem.
Then yesterday I disconnected the plug before going back home. It fired up right off and at first the idle was a bit wild, too high, around 1500 rpms, like the choke in the old cars. After a couple of minutes driving it went down to normal, either when driving at low speed or idling, and this morning is still normal. I think the ECU realized there's no stepper motor after those two minutes, and "learned" to run without it, probably going back to best known or compromised mix values. I even think that runs a bit better than before, a bit more brisky...
My question is, there has to be a downside of running with the stepper motor disconnected, anyone knows? I mean if it runs perfect without it, they wouldn't have put it there...[;)]
Thanks /S.

AndersDK · Post by **AndersDK** » 12 Aug 2003, 17:29

Winter comes - you'll soon see why the stepper motor must be fitted [;)]
It MAY be something else teasing you -
The ECU controls the stepper motor based on various sensor informations - the engine temp sensor used for "choke" - exactly at start up on cold engine.
Look over your engine to find a 2-pole sensor - usually near the thermostat housing. The connector block may be blue or green plastic.
Don't mix up with the 1-pole sensors for temp warnings on instrument panel.
This 2-pole sensor is an ohmic sensor - should have approx 3.5Kohms when cold - decreasing when hot. But the problem may simply be a dodgy connector/cabling.
Anyway the sensor is much cheaper than the stepper motor.

SuperSerdo · Post by **SuperSerdo** » 14 Aug 2003, 01:02

Thanks mate! I'll give it a shot. I looked in the Haynes manual, I guess you mean the air temperature sensor that's underneath the throttle body. Thanks again /S.

AndersDK · Post by **AndersDK** » 14 Aug 2003, 01:39

No - I do in fact mean the engine temp sensor [:)]
This is MUCH more prone to go dodgy than the air temp you talk about.

SuperSerdo · Post by **SuperSerdo** » 10 Sep 2003, 20:14

In case anyone's interested, the other day I had to get a new battery as the original one died after 7 years, not bad... Anyway the new battery fixed the starting problems I had, which I tought was from the stepper motor!!! Good I didn't get a new stepper motor!!
So it looks like the old battery was powerful enough to crank the starter, but not to feed the electronics, then it would work just fine when the alternator was taking over the electrical source of power. There's always more to the problems than it may seem at first look....