DamirGTI 329 Posted June 26, 2007 Hello ! I have some problems regarding idle speed : I've set idle speed around 1000-1200rmp , it varies a little bit up and down but as we know already this is "normal" for these cars .. However when cooling fan cuts in revs drop down to 500-600rmp constantly varying with idle speed from 400-500-600 up and down all the time Ive try with another alternator but it isn't better , also Ive try thousands combinations of idle speed settings another TB , check for air leaks , another AFM but with no luck Engine is fully rebuilt this year , electrics also Ive repair all bad wires and clean connectors , mass wires to chassis .. What can be wrong ?!? Thanks ! Damir Share this post Link to post Share on other sites
Richie-Van-GTi 70 2 Cars Posted June 26, 2007 if the fans effect it so badly then its got to be current related as the fan motors draw a fair chunk of current. Possibly the fuel pump is losing pressure due to current drain? Share this post Link to post Share on other sites
DamirGTI 329 Posted June 26, 2007 maybe how can i check this ? Share this post Link to post Share on other sites
welshpug 1,629 Posted June 26, 2007 hook up a fuel pressure gauge and see what happens when the fans kick in, have you cleaned the earth point for the fuel pump? Share this post Link to post Share on other sites
DamirGTI 329 Posted June 26, 2007 ok. will do that pressure test I'm not sure about this fuel pump earth Ive clean all earth points in the engine bay , where is fuel pump earth point ? Thanks Damir Share this post Link to post Share on other sites
rocky 0 Posted June 26, 2007 The same happens on my 205MI, the idle speed doesnt drop below 1000rpm but it just hoevers around this mark when the fan cuts in. I think my timing is out though and the engine needs a tune... Share this post Link to post Share on other sites
lee-bg 0 Posted June 26, 2007 same thing here on my mi16 ) fan starts and revs move and car idle is unstable. New Battery fixed things, but not to 100%. So still having this problems. I am suspecting the AFM ..and/or TPS for some reason..also it happens if the car is in motion at certain revs....it just looses for a second then continues. I am positive it has something to do with 'current being drawn' and usually when fan kick in. if i find a cure before you i will post. Share this post Link to post Share on other sites
Pugnut 9 1 Cars Posted June 26, 2007 Hello ! I have some problems regarding idle speed : I've set idle speed around 1000-1200rmp , it varies a little bit up and down but as we know already this is "normal" for these cars .. However when cooling fan cuts in revs drop down to 500-600rmp constantly varying with idle speed from 400-500-600 up and down all the time Ive try with another alternator but it isn't better , also Ive try thousands combinations of idle speed settings another TB , check for air leaks , another AFM but with no luck Engine is fully rebuilt this year , electrics also Ive repair all bad wires and clean connectors , mass wires to chassis .. What can be wrong ?!? Thanks ! Damir same thing here on my mi16 )fan starts and revs move and car idle is unstable. New Battery fixed things, but not to 100%. So still having this problems. I am suspecting the AFM ..and/or TPS for some reason..also it happens if the car is in motion at certain revs....it just looses for a second then continues. I am positive it has something to do with 'current being drawn' and usually when fan kick in. if i find a cure before you i will post. its a trait of the jetronic injection unfortunately , but not really at the levels you are experiencing. I've found in the past that if the battery is on its way out you load up the alternator more than necessary. Its just another thing for you to check. I would try and borrow another known good battery just to rule it out. as mentioned you could have bad earths too cheers, Al Share this post Link to post Share on other sites
DamirGTI 329 Posted June 27, 2007 same thing here on my mi16 )fan starts and revs move and car idle is unstable. New Battery fixed things, but not to 100%. So still having this problems. I am suspecting the AFM ..and/or TPS for some reason..also it happens if the car is in motion at certain revs....it just looses for a second then continues. I am positive it has something to do with 'current being drawn' and usually when fan kick in. if i find a cure before you i will post. Hi ! Please ! it will be very nice to know what causes this Anyway I've check fuel pump wiring today , clean earth wire of the fuel pump and repair all connectors also I've check positive fed wire to pump (the wires was a bit ugly looking but nothing serious me thinks ..).. i will try driving later and see if there is some improvements cheers Damir Share this post Link to post Share on other sites
DamirGTI 329 Posted July 3, 2007 Hi ! Well .. - bugger it's not the battery I've fit new yesterday , clean all the earth wires i can find inside and outside of the car , also I've check-repair all positive wires and make new connections to the battery terminals but still no good - idle swinging up and down Must be something else but WTF ?!? i don't understand this .. Share this post Link to post Share on other sites
DamirGTI 329 Posted July 11, 2007 Hi ! Little update if somebody is interested in this : I've fixed this bloody wandering idle speed and the solution was : Tight the AFM spring tension for one tooth , unscrew the mixture screw (on AFM) half turn out (7.5 turns from fully in..) raise idle speed for 100rmp with the air screw on TB and bob's your uncle The car runs sweet even when the cooling fan kicks in the revs don't drop any more and don't swing up and down Regards Damir Share this post Link to post Share on other sites
Guest jarrods Posted July 14, 2007 The drop in revs is caused by the alternator loading up to compensate for the addition current being drawn by the fans. If you have a weak idle (mixture wise) it will be much more pronounced. Jarrod Share this post Link to post Share on other sites
DamirGTI 329 Posted July 15, 2007 Hi ! Yes this uneven idle + revs dropping/varying is mixture related I've try one test today just to see what will happen : i loose the AFM spring tension again for two tooth more and jerky idle is back (also revs swinging from 400-500-400-600rmp up and down when cooling fan kicks in) so this is 100% because of the rich mixture me thinks , well at least on my car .. When i tight the spring back this symptoms vanish and idle is stable even with cooling fan working .. Hope this helps to somebody in the future with similar idle problem Regards Damir Share this post Link to post Share on other sites
mossy 0 Posted July 16, 2007 An over rich mixture or lean mixture will do this. Due to the simplicity of the engine electronics you need to have the air/fuel mix spot on. Don't go playing with the AFM Spring tensioner if you don't have a gas anilizer. If the Mixture is to week at higher revs, you'll probably destroy the engine. Just a warning to you ALL. Share this post Link to post Share on other sites
DamirGTI 329 Posted July 16, 2007 An over rich mixture or lean mixture will do this.Due to the simplicity of the engine electronics you need to have the air/fuel mix spot on. Don't go playing with the AFM Spring tensioner if you don't have a gas anilizer. If the Mixture is to week at higher revs, you'll probably destroy the engine. Just a warning to you ALL. Yes i know that very good , i measure Air/Fuel ratio via lambda sensor (not an exhaust gas analyzer) for adjusting/checking the mixture .. and my AFM was adjusted on rolling road (but was setted one tooth too rich and also i have an adjustable fuel pressure regulator because of my modified engine/head and I'm playing with the pressure from time to time so must compensate that by adjusting the AFM spring tension also , but as i sad i don't go more than one (maxi. two) tooth clockwise or anti-clockwise on the AFM ... i have bigger injectors also etc.....) and this was just a test , one tooth more or less from the middle standard settings want do too much trouble on the mixture at any rev range me thinks if you go more than 7 tooth on the rich or lean side well then you can get in trouble cheers Damir Share this post Link to post Share on other sites
