How to check stepper motor? -updated

This is the Forum for all your Citroen Technical Questions, Problems or Advice.

Moderator: RichardW

Post Reply
pagh
Posts: 36
Joined: 31 Jan 2005, 03:19
Location: Denmark
My Cars:
x 1

How to check stepper motor? -updated

Post by pagh »

Hello
I have engine problems with my 1995 Xantia 1.8 8v with 272.000 km on the clock.
It kinda hesitates when doing a normal accl, especially when doing 1500-3500 rpm. It`s very "raw" when taking foot on/off accelerator.
When going under ~1800rpm, with foot off accl., it kinda pushes the car.
I have read a lot of threads on the forum, and i think i homed in on the stepper motor. I have it lying here on my table, but can i dismantle it, so i can give it some grease? It is Magnetti Marelli.
How can I check if it is faulty?
I have also tried to give the thottle pot. a little grease but that didn`t help. I then disconnected the stepper motor with warm engine, and i couldn`t feel a change in behavior.
Also, is it normal that the housing for the step motor is rather oily, or should i clean the whole thing?
I hope you can help me, because it is getting rather annoying.
I`m from Denmark, so my english isn`t that good.
If in doubt of anything, just ask.
Stuart McB
Posts: 1635
Joined: 03 Oct 2003, 00:50
Location: United Kingdom
My Cars:
x 1

Post by Stuart McB »

Ok . First wipe over and then spray in every port or hole carb cleaner. Spray until it runs out clear. Then once dry spray with the WD40 silicone spray in the same places as the cleaner. Allow to dry then refit. You can take them apart but it's a right pain. That oil is from the induction side of the manifold, it's the result of the burnt oil vapour from the cam / rocker cover condensing and forming back into oil residue deposites. Best to give the piping a clean that leads to the stepper. All so if you can give the throttle body a good clean out. Unplug and remove from the manifold, only about 3 allen heads or so then grease and replace. Not a big job at all. You can also remove the throttle potentionometer as well while the body is off. Re-grease and re-fit. I hope this helps.
LeFrog
Posts: 79
Joined: 12 Aug 2004, 13:44
Location: New Zealand
My Cars:

Post by LeFrog »

Stuart is on the mark with his post, but your symptoms don't sound like a stepper motor to me, particularly as you don't even mention any idle problems.
It sounds very much like a spark problem to me. A problem I had with a previous car. Can I suggest that you check them, if you haven't already?
pagh
Posts: 36
Joined: 31 Jan 2005, 03:19
Location: Denmark
My Cars:
x 1

Post by pagh »

StuartMcB ->
Thanks for the reply. I will look into it.
LeFrog ->
Hmmm, ok. I have recently changed sparkplugs, oil, oil filter, air filter, fuel filter and fuel pump, no change. But could it be the sparkplug-cables?
I don`t have idle problems, i don`t think so. It is around 600-700 rpm at idle, but if i have it at high revs, and then use the clutch, it often goes around 1100 rpm for ~5 seconds, and then drop to the usual 600-700.
The car starts without problems, even with cold weather, no problem.
It doesn`t use to much oil and fuel.
Any ideas?
User avatar
AndersDK
Posts: 6060
Joined: 21 Feb 2003, 04:56
Location: Denmark
My Cars:
x 1

Post by AndersDK »

Hej Michael -
If you suspect a sticking steppermotor - it would be possible to see it down the intake while you testrun the engine.
The steppermotor is nothing but an electric idle control by the ECU.
Check the throttle axle & cable as it may stick mechanically.
pagh
Posts: 36
Joined: 31 Jan 2005, 03:19
Location: Denmark
My Cars:
x 1

Post by pagh »

Hi all
After surfing the web, i found a danish page, where a guy has the exact same problem as me.
It is a page where people can ask for help, and educated mechanics answers their question.
He has changed the following things without luck.:
MAP-Sensor
Idle speed stepper motor
Thottle potentiometer
spark plugs
spark plug cables
checked lambda sonde, was OK
He is given the advice to check his ground connection`s, and if that doesn`t help, then change the fuel pressure regulator.
Link to the page: (text in danish)
http://www.netrep.dk/e-mails/motor-inds ... n_gang.htm
Then choose "Citroën Xantia 1.8i 8v '93 - nykker ved jævn hastighed."
Of course i will check things out tomorrow, but what do you guys think, could these 2 things be the problem?
alexx
Posts: 462
Joined: 19 Nov 2002, 02:42
Location: Slovenia
My Cars:

Post by alexx »

As I described several times, I also have a similar problem (1.8 16V, '98). When pressing the throttle sharply, engine reacts quite abruptly after a little delay. Usually about 0.2-0.3 sec, sometimes maybe near 1 sec. This problem is present if the pedal was previously released or pressed less than about a half (especially during gearchange), otherwise not. If I press the pedal gradually, everything is ok (or almost). No other problems with the engine.
I had the car checked with diagnostics, but it didn't show anything wrong - all sensors (MAP, throttle potentiometer, temp. sensors, lambda probe etc) were giving expected values, no error codes etc. Spark plugs and fuel filter were changed short ago, at 60.000 km, but no improvement.
I think it's possible that pressure regulator is somehow sticking and isn't reacting quick enough, especially considering that quality of the fuel isn't very high in our country. But, how to check it ?
pagh
Posts: 36
Joined: 31 Jan 2005, 03:19
Location: Denmark
My Cars:
x 1

Post by pagh »

Alexx ->
I will clean my ground connections today when i get home from work. And if that doesn`t help, then i will get another fuel pressure regulator. Depending on the price here in Denmark, i will either go to the scrappies, or buy a new one. But if I know the danish prices correct, i will most likely buy a used one. :-)
I have to get this fixed, because im due to MOT in about 3 months, and i don`t think my emmissions are so good.
I will of course post my findings on this forum.
alexx
Posts: 462
Joined: 19 Nov 2002, 02:42
Location: Slovenia
My Cars:

Post by alexx »

In my case, emissions were ok. Also, this engine hesitation didn't get worse (nor better) since I bought the car about 1 1/4 years ago. And another thing, two other members of our local forum reported similar problems with this engine.
In my case, I don't think this is due to the bad electrical connections. Main ground terminal near the battery is shining like a new.
I'll experiment with this when the weather warms up a bit. Maybe disconnecting the vacuum pipe of the regulator will show something, or it may be leaking. Will also check throttle potentiometer with analog ohm-meter.
I didn't find the prices for the regulator over the internet. Probably about 50 EUR, i think.
pagh
Posts: 36
Joined: 31 Jan 2005, 03:19
Location: Denmark
My Cars:
x 1

Post by pagh »

GSF has the part for around 34-36 pounds + shipping.
My local citroen dealer, want`s a bit more, around 70 pounds.
So i will make a visit to the local scrappie.
alexx
Posts: 462
Joined: 19 Nov 2002, 02:42
Location: Slovenia
My Cars:

Post by alexx »

Thx.
pagh
Posts: 36
Joined: 31 Jan 2005, 03:19
Location: Denmark
My Cars:
x 1

Post by pagh »

Ok, i was just at the scrapyard, he had one. I got it for around 4 pounds.
There was a plastic ring on top of af rubber-ring, and that plastic thingy broke on the one i bought. I don`t know if it actually has anything to say, if yes, then i will somehow need to pull it off the old one.
But damn, i can`t mount the new one, nor the old one. You`ll have to push real hard to get it into the hole again. But do they mention it in Haynes, noooooo....of course not. :-(
I will try with some food-oil on the rubber ring tomorrow, and hope it will do the trick.
But hey, then i have an excuse to take my parents 1986 Volvo 740 Turbo to work. It has a "little" more power than mine. :-)
alexx
Posts: 462
Joined: 19 Nov 2002, 02:42
Location: Slovenia
My Cars:

Post by alexx »

Yes, latest editions of Haynes aren't very descriptive like older ones. In the book, pressure regulator for 16v engines is shown, and it seems that there is only an o-ring on it (marked with an arrow on the fig. 13.10b). It could be a different type for 1.8 8v.
What is the manufacturer of that thing anyway? Can't find much info about pressure regulators on the net.
pagh
Posts: 36
Joined: 31 Jan 2005, 03:19
Location: Denmark
My Cars:
x 1

Post by pagh »

I will have a look on the regulator when i get home.
Yes, it looks like theres only that "big" o-ring in haynes, and no plastic thingy.
But "ease" the thing out, according to haynes, yeah right.
I got mine from a 1.6 Xantia, it was the same as mine.
Maybe i should use a hammer to get the damned thing into place?
Oh well, we will see.
alexx
Posts: 462
Joined: 19 Nov 2002, 02:42
Location: Slovenia
My Cars:

Post by alexx »

Forgot to mention earlier - I also noticed that, after switching the engine off on my car, there is some hissing, coming somewhere from fuel rail or pressure regulator (definitively not from hydraulics), and lasting several seconds. I don't know if everyone else noticed this and is this normal behavior or not. I would expect maybe half a second, until the regulator close the return pipe.
Found a picture of PR for VW Passat, made by Bosch. It looks very similar to that one in Xantia, and really - there is an orange piece of plastics on the bottom of it, under the o-ring
Post Reply