Stepper motors, throttle body, etc.

[Simo]

The Saxo is prone to problems with the stepper motor, throttle position sensor, MAP sensor and the complete lambda control system in general...

My car, like many others stalls from time to time when it's hot! And YES, it really is annoying!! smileys/smiley7.gif

I'm determined to cure this problem...

I will post updates as and when I find things out.. feel free to contribute to this thread.

Before I say what i've done so far to help eliminate the problems, I thought I'd show you a pic of the throttle body internals and the stepper motor itself, as many peeps don't know what they look like.

So here goes...

http://www.sax-p.com/stuff/steppermotor1.jpg

http://www.sax-p.com/stuff/steppermotor2.jpg

http://www.sax-p.com/stuff/steppermotor3.jpg

http://www.sax-p.com/stuff/steppermotor4.jpg

[ciars]

Lambda went on mine during warranty period. Had it replaced FOC thank god. Very common fault, specially in Mk1's...mine was just under 2yrs old at the time.



For the lucky ones not to have suffered it (yet), you'll know as your car will start after a couple of attempts...you'll rev it to keep it ticking over then you'll feel it dying away, even if you give it more juice to try keep it tick over. Like the engines been starved.

[Predator_R32]

hey simo so do u know how to do it yet or not cos mines doin it a lot now!!! I NEED HELP

[Simo]

It's easier to see when your lambda system is and isn't working using an AFR meter..



"My" lambda system is only supposed to cycle when on idle or light throttle... About 60% of the time it does cycle as normal.. the rest of the time it stays in the rich section... (last green light/1st red)



Obviously something in the lambda system isn't getting the correct signals, or is not able to react quick enough..



Probably the biggest suspect is going to be the lambda probe itself... but being quite an expenxive sensor, many people will choose not to replace this straight off.



Next in line is going to the the stepper motor, air temperatures sensor and TPS.



I've started my diagnosis my moving my air temps sensor out of the inlet air/fuel path. In case rapid temp changes when on/off boost with petrol spray were affecting the probe...



With the air temp sensor moved.. no benefit has been seen to lambda control when warm.. or has it improved stalling issues.



BUT, it must be temperature related... if not air temp/density when the engine is warm, then maybe water temp... or even sticking stepper motor when hot and with additional fuel spray??



The story goes on...

[saxovts391]

Ive just had the lambda probe replaced on my vts. Mine still has poor idling, do you know any ways of making it better?. Someone said to me a power boost valve helps?

[ManicAJK]

i've had probs with idling for ages, when at idle my rpm gauge bounces up and down like a yoyo going inbetween 1200rpm and 900rpm, also when on light throttle sometimes the car jerks, it's ok on boostetc so i know it's not related to my MF2 or sigcon2 unit. So far I have replaced the TPS and stepper motor, problem still remains. Next on my list is the standard map sensor (and temp sensor as it is a combined unit on my car) and lambda probe as last resort cause they're bloody expensive!

[Simo]

My car idles fine.... but you start feeling/hearing the idle get lumpy as the fuel ratio steps down to lean... sometimes goes off scale before correcting and stalls (so maybe lambda probe?)



Standard MAP sensor is a good point, as it still uses that when off boost... (forgot about that).



When driving on light throttle and lambda is cycling, my car jerks everytime the fuel ratio cycles down.... its a quick cycle of the afr but you do feel like you're kangaroo'ing down the road a bit.



Everything is fine when on boost, as theres plenty of fuel etc...



My problems seem to focus around running temp and lean fuel under some conditions. I know lean can be effected by stepper, air temp etc.. which is why its a bit of a ballache.



Simo'

[RID VTR]

Try checking the conections on the feul pump and checking the pump itself.

My mk1 vtr had very similar symptoms as you have discribed and it was finally traced bac to the fuel pump so they replaced it and it seems to have solved the problem.

The citroen dealership that did the work had told me that the week befor they had a vts doing the same so they replaced the pump on that and it cured had the problem.

[axsaxoman]

the postion of the sensor will have an effect as the temp of the probe will alter the voltage sent to the ecu.also it could be ,or probably is the fact that the probe you have fitted is not meant to be fired by the heat from the turbo, you could try fitting a dif type of sensor ,ie the same as is in the afr meter?. or an lsm11 ,(bosch motorsport type ,also fitted to most turbo cars) these cost approx £130+vat. then you could fit a even more exotic type one. this is not a turbo only problem. the s/c cars can do the same sometimes ,but not as bad.

[axsaxoman]

other things which i have found that cause poor idle in my experimentations are. incorrect valve timing (even on std cams at std setting). swinging exhaust cam can improve it greatly, or poor hydraulic followers ,not bad enough to rattle ,but enough that the valve openings are uneven at idle speed. engine breathing a little from breather on inlet cam cover into induction tract or the small pipe into the throttle body. the oil vapour burns ,gives a highe reading and so the ecu thinks its extra fuel. it can also polute the sensor so it changes slowly. a slow changing sensor is indication it is getting worn. cam belt too tight or loose will cause same. the reason why some cars respond well to fitting a 4.5 bar fuel reg is that the injectors are getting dirty or not spraying a good pattern at low flow rates and so increasing pressure makes them work better

[axsaxoman]

stepper motors can become lazy as well , they get very hot sometimes and jam , the housing they fit in get full of shit,an indication of poor air filtering or excessive engine braething causing oily residue, clean out housing etc.an air leak on the inlet manifold anywhere ,even past an injector seal can cause same poor inconsistant idling

[axsaxoman]

T.P.S sensor is not likely to be problem ,and one you can measure easily with a volt meter to see if voltage is changing ,if not then its ok. open throttle slowly and look at voltage ,if any blank spots the meter will show it ,or if the voltage drops as you open it it will show it

[axsaxoman]

irratc fue lpressure certainly will cause it ,change filter regularly, I have had problems with power boost valves not being steady pressure. and lastly any sort of poor earth or power connection anywhere on electrical system or dodgy alternator can cause it .the ecu only sees voltage so if the supply alters beyond a cetain amount then the ecu will not like it

[Simo]

Thanks for the comments John... I have a few things to check...



I remember noticing some time ago that the exhaust cam timing appear to be almost on full swing (cant rememebr which way though) I shall take a look later. Any recommendations for approx position?



As for head breathing oil mist back into the inlet.... my rocker breather currently feeds into an oil catch tank and then vents into the inner wing. I have kept meaning to pipe it back into the inlet side, so as to pull the vapours out of the head. could have an effect on idle?



I also thought about swapping the AFR probe for the one the ecu sees... maybe it will operate better? And after swapping, if I dont see the afr cycling properly, I know the standard probe is probably shagged. <img src= "smileys/ponder.gif">



The prob about the afr not cycling properly sometimes could be residual fuel in the inlet pipe?? getting blown through for a short while? (hopefully not the case though)



The story continues... <img src= "smileys/wink.gif">

[Simo]

One thought.. I know we tested the behaviour of my power boost valve when on the rollers.... but when the car goes on boost... what did the pressure do? stay the same or surge up or down?? <img src= "smileys/confused.gif">



Simo'

[axsaxoman]

just while I remember i had one vtr that the lambda readings were offset by 2% c0 reading ,after weeks of trying everything it turned out to be a wiring loom fault ,excessive electrical noise inside the loom was distorting the value of lambda seen by the ecu.so do not run extra power wires close to std loom unless they are very low current ,and not a pulsing type of signal .i have seen a signal from a coil pack (ie coi swithcing on and off as it sparks ) causing crank sensor to show rubbish to ecu ,same applies to lambda ,all wires are shielded in the loom for both crank sensor and lambda loom

[axsaxoman]

as i remember it was steady but is it at idle?. thats why i like the injectors clost to t/body ,but no i don,t think it will bw that more likely poor pattern from std ones at idle ,drops running down the port instead of being atomised.thats the reason why modern cars have injectors so close to valve ,for emission not power. best place for power is at end of trumpets,but only above 5-6k. below that best is mid inlet manifold length to alloww evaporation of fuel into a nice gaseous state.

[axsaxoman]

presuming std cams ,and the lock pins fit in correct place,ie crank one and two cam pins ,then move ex cam forward ,ie retard the valve timing a couple of degrees.then check it all still is not touching before starting engine.or you could move inlet cam the other way a bit

[axsaxoman]

when cam boxes are ff is good time to check followers for squish. with knobbly bit of cam upwards the follwers are at their loosest. if you can press them down any decernable amount , then they are buggered. if only one or a couple are that way then you will have different valve timing on different cylinders causing the uneven running at idle ,same with incorrect tightened cam belt

[trickyd]

Mine tends to do this if I drive it hard. Leave it idling for a minute or 2 the A/F drops off the guage for a second and car almost stalls, thought it might have been fuel percolation, but high lambda temp seems a better explanation.

[Simo]

Just a quick look at the cam timing... Like I said, the exhaust timing seems to be quite offset from centre... but inlet seems to be centred.

I know you cant tell too well from a pic of the pulleys, but its an insight...

http://www.sax-p.com/stuff/caminlet.jpg

http://www.sax-p.com/stuff/camexhaust.jpg

[axsaxoman]

if the engine is on tdc then the valve timing is incorrect. lock flywheel with lock pin (6mm rod) then put 8mm lock pins in cam wheels.then take a piccie

[Simo]

No that was NOT at TDC... I will align and re-take pic later on..



SImo'

[ManicAJK]

just a quick note, double check all earth points particularly if using extra trickery like sigcon units as i traced my didgy idling back to a faulty sigcon unit earth!

[Alex2001mk]

I have my Saxo stalling all the time when the engine is hot. I had my lambda fail on my VTS (and also few years back on my Ax Gti) as soon as I fitted the Supersprint system. The day I installed the de-cat pipe (replaced cat+mid section) and the back box my lambda filed.



The info I got was that without the cat the lambda cannot work properly so even if you replace it the fast hot exhaust gases from the manifold will torch it again. I have been thinking about this and came up with a solution. The lambda value varies from 100-1000 (mVolts or whatever) so if you build a dummy device that would tell the ECU that the lambda is on 500(around normal value) you would not have as much problems. The device will be easy for any electronic geek to make.



Also you might want to check the AirFlow sensor on the intake manifold, especially the wiring because I've seen the wires get lose because from vibrations on many VTS's, which results to uneven acceleration and stalling. This is a sensor that influences the mixture a lot and its crucial for making quick changes in the mixture on acceleration.



PS: If anyone knows what pressure I should set my FSE this will be a good time to tell me!! (I have a WRC K&N Induction System + SuperSprint Exhaust System



Hope this info helps.



Alex

[Kevstar]

Hi guys, wondered what you think to this...



The car has been in storage for 6 months which may or may not have anything to do with it however for a month after getting it out it has been fine.



Basically the car idles very lumpy somewhere between 5-700 rpm and occasionally cuts out. This is worst when coming down from high revs and will cut out without any load. There is no obvious signs of anything while driving. Its also the same when cold or hot.



I can't spot anything obvious so I tightened the throttle cable so it doesn't cut out but obviously I'm keen to get to the bottom of it. I've cut some carb cleaner and going to clean the various sensors and the throttle body and also some injector treatment.



Personal thoughts are either that its either the tps or stepper motor.

[louistheroux]

Does anyone know what the symbtoms are and how to check if the knock sensor is the problem?

[Simo]

Ive still not got to the bnottom of thios problem... but have a few ideas to trial...



I've had the stepper motor apart again and am learning about how it works.. When ignition is on, it pulses all of the way out.... ignition off, it retracts all of the way.



My problems seem to get worse when the thermostat opens... which would suggest that either a temp probe is dodgy, or the ecu itself does NOT like running once its on its "warm" map??



All last week my lambda was static in the red, with shit coming out of the zorst due to unburnt petrol... this week ive driven for 3 days without boosting up at all! This has meant the lambda system has been working for 90% of the time... but still stalling when warm.



Certainly seems to suggest petrol spray on the stepper could be the cause though..



The saga continues...

[Simo]

smileys/bumpit.gif

[Scott]

and have you fixed it yetsmileys/smiley17.gif

[GreenSaxo]

lol.. old posts rock! smileys/smiley17.gif



as scott says.. u sorted it yet??

[Scott]

just to add to this: all my stuttering, stalling and erratic idle disappeared when my coil pack died and i replaced it with a new one

[GreenSaxo]

mine does the silly revving thins some times..

but not very often does it get to idle... or drop below 3500rpm smileys/smiley17.gif

[CoolFusion]

The answer is very easy...i had the exact same problem with mine. All it took was to replace all sensors on the throttle body and the coil pak. smileys/smiley14.gif

trust me...it did the job,with an addition...car runs better and faster!! smileys/smiley10.gif smileys/smiley10.gif

[Alex2001mk]

Simo!

Take a glance of my post in the VTS Gremlin thred. My problem seemed to be the MAP sensor, or the new MAP is ironing the small faults throughout the engine.

AXSAXOMAN might be right on the valve timing, because I had my inlet cam retarded on my previous cam belt and the problems were not that noticable. After I changed the cam belt I I used standard setting because I have no idea how to set them other than this. Then the problems with the idling and cruising cut-outs started.

I feel acomplished. I think I'm gonna get myself a beer.

[axsaxoman]

if the ecu is going wobbly when it gets hot ,you can try spraying it with circuit board cleaner or even a proper cooling spray ,if the prob goes then it will be a dry joint on the board somewhere.

[ManicAJK]

i wouldn't fancy getting my soldering iron out on an ecu PCB. If it is a dry joint then i suppose you either try to locate it and re-solder it or go down to your scrappy and find a nice VTS. Get the ecu, transponder unit, chassis number etc and take it all to citroen with all your keys and get everything swapped over and recoded.
I did it and it wasn't that hard or costly.

[goenie]

any1 got a defenate solution/answer on this issue yet? Simo?

I'm also experiencing the crappy idling and the so-called kangaroo'ing... smileys/smiley5.gif

It's quite annoying to say the least.

[citrovts]

try a GMC FPR there good for helping your crappy idling

[alsax]

My girlfriends W reg 1.1 forte has a lumpy rev when hot.
Her M plate 106 1.1 did the same when hot too.
That was fixed by slackening the cam belt that I fitted too tight.
I was told on another forum that as the engine warms up it expands enough to tension the belt very slightly.
A too tight belt WILL cause a rough idle.
Worked on the 106, Going to have a look at the Saxo next, though that belt was fitted by the factory.