205 Gti 1.6 Revs Drop When A Electrical Load Is On?

[Guest mjs87]

hello there i have a slight problem with my pug it seems to run pretty good when there is no electrical load been put on it say like in the day..... i do notice when you rev it, when the revs drops it seems to drop abit too far say 950 then sits steady at just over 1000 where it stays sort of bounces like once if you know what i mean but say if i put my headlights on the revs drop and keep dropping if you add say the heater and rear heated screen i have change the alternator and batteryalso cleaned the battery earth anyone help that would be great thank you also i will add when i have my headlights on if i rev it and the let it drop my lights dim slightly then brighten to normal when the bounce has done as such does that make sense thanks guys

[damo 17 2 Cars]

my pug does the same, I've been told its normal on tick over and tweaked the idle whilst under full load.

 

set it to 800 ish with the lights, heater etc on. with everything off its around 1000 rpm. checked with mechanic at college and this is right, things do cause a load when idle as the altinator isn't fully charging until the revs are higher.

 

i hope this helps, it sounds normal. is it down on power when driving?

[Guest mjs87]

no it seems fine no problems with power didnt know if it was just mine or not so there isnt really a problem with mine then where is the idle screw so i can lower mine a tad its 1992 k reg also i find my choke has slightly gone up it settles fine when warm it used to be around 1500 now its about 1700 can this be adjusted?? thanks for your time Mark

[simonb 0]

I have spent a long time trying to get my head around this problem when all electrical connections seem good etc. The best fix for this I have found is to play with the ignition timing. When this is set correctly so that there is no pinking under full throttle/load, I found that the idle speed when the electrics were on only dropped about 50 rpm below where it idles with all electrics off.

 

My car idles nicely at 900 rpm when hot and I don't have a high idle after giving the car a good ragging; however some drop in idle speed is normal as these cars don't have any form of idle control valve and the electrics place an additional load on the alternator.

[Guest mjs87]

I have spent a long time trying to get my head around this problem when all electrical connections seem good etc. The best fix for this I have found is to play with the ignition timing. When this is set correctly so that there is no pinking under full throttle/load, I found that the idle speed when the electrics were on only dropped about 50 rpm below where it idles with all electrics off.

 

My car idles nicely at 900 rpm when hot and I don't have a high idle after giving the car a good ragging; however some drop in idle speed is normal as these cars don't have any form of idle control valve and the electrics place an additional load on the alternator.

 

ok thats sounds pretty good wish i could get mine like that!! how can i adjust the ignition time dont like to sound stupid but i might aswell ask thanks

[simonb 0]

You need to rotate the distributor. This is done by undoing the two 11mm bolts and rotating it. Standing at the front of the car:

 

1. Rotate anti-clockwise to retard the timing.

2. Turn clockwise to advance the timing.

 

However - I have just seen that your car is K reg and on this model (unless an older Jetronic ECU is fitted), it will not be possible to set your ignition timing using this method as it is controlled by the ECU. The only thing you can do is adjust the throttle stop screw and the idle-bypass screw. These are both located on the throttle body.

 

Have you checked the inlet pipes for air leaks as 1500 rpm sounds a bit high for a warm idle. I suppose it could also be you cold start valve (S.A.D) sticking open when warm or a sticking throttle butterfly. Try a search for things like "high idle" to start you off.

[sNaKePiT 1]

My Pug done this loads, but now idles at 600 rpm with no movement up or down due to a m8 setting up the idle valve on the throttle body and the screw on the airflow meter. This will also help any smokeyness due to high CO2 levels.

[Tilly205 0]

possible a low charge from the alternater?? have u checked voltage ?

[Tilly205 0]

possible a low charge from the alternater?? have u checked voltage ?

[Beastie 1]

There is a perfectly good reason why this is happening and it has nothing to do with bad connections:

 

When you increase the electrical load (by switching on headlights etc) then there is an increased drain on the battery. The regulator in the alternator responds to this by increasing alternator output in order to balance the load.

 

If you are taking energy out of the alternator in the form of current then energy has to be put into the alternator from the engine.

 

Therefore when you switch on the headlights it's actually the engine that is powering them. All older engines slow down a little when the load increases on the alternator. If your 205GTI drops a fraction in revs then it's normal. If it drops considerably in revs and / or starts to run badly then it's because the engine is not running properly - maybe because the ignition timing is out but not neccesarily!

 

Modern engines have engine management which controls the idle speed so that this phenomenon doesn't happen.

[DamirGTI 327]

Hi !

 

Another vote for the ignition timing , if it's everything fine with the alternator/wiring then i would suggest you to try and adjust the ignition timing but check the fueling first and re-adjust as needed (with the idle mixture screw on the AFM , also if you feel brave enough whip off the AFM cover and play a little bit with the spring tension .. but with great care !)

 

Anyway I've had this problem for a long time and been investigating a lot and me thinks that it could be :

1 alternator

2 air/fuel ratio

3 ignition timing

 

I've fix my engine first with adjusting the AFM spring tension (tight just one tooth) adjust the AFM mixture screw reset the ignition timing reset the idle speed with air screw on the TB and bob's your uncle

 

Best luck !

Damir