Engine is dying when lights are on

Hey guys,

I need to post in project thread with my mk1 when I get the time

Have a problem at the moment, the engine is a 1.8 16v kr from a mk2

Recently had the engine timing all sorted running a lot smoother and fine but all of a sudden I turn the lights on, and the idle rev goes down at 0.5k revs choking and dies every time. The revs are a lot sharper and drop down a lot quicker. I have to keep reving and left foot brake when stopped, is this an alternator or battery problem? when I drive the engine chuggs a lot like as if im doing 10mph in 5th gear when im actually doing 50

Help appreciated, thanks

Sounds like a lack of electricity maybe, does it do it on any other high ampage demands eg, blowers, rad fan or only the lights?

Sorry for late reply. When blowers are on the idle does decrease very slightly, but totally dies with lights on.

Thanks

Sounds like a faulty alternator. Can you measure the voltage of the battery (/alternator, it will be pretty much the same) while the engine is running and lights are off-on? I suspect what's happening is the alternator is overchcharging when a small load is applied. Normally it would try to stabilise the voltage and supply whatever's needed, but it might be overdoing it.

Its a bit of an odd problem though, even if this was occurring, the engine should cope with full alternator output required while more/less idling. What controls idle speed on your 16V, there's a few different ways to arrange things (either use the AAV of the Mk1 GTI, or transfer the module and ISV etc).

Cheers for the reply, haven't got a volt meter to use =/ would a different alternator fix the problem or could this be a wire/battery problem?

It only started to happen when i took it psi tuning to get the engine setup tuned. I'm not to sure I know it has a k jet fuel system

Waste of time replacing the alternator until you know what the fault(s) is (are). If its been to psi tuning and its running worse/now has a fault, withhold their payment or take it back to them.

I paid when they did it, it was done on thursday but only noticed it saturday night as was first time drove it at night time with lights on since it was done.

This does sound like an alternator problem really. I'd take it back to where you got it tuned and ask them to stick a volt meter on it.

Also get them to check the volt meter at the battery and what voltage the alternator is kicking out. This is because I had a really bad contact at the starter motor, all the connections were really corroded  and the alternator was dropping all its voltage on that connection.

Do you have any problems starting your car?