Problem with engine when headlights are on
 

I've had this problem for quite a while now. Basically whenever the headlights are on these are the symptoms:

- When you touch the accelerator there is a lag of about half a second, before the revs suddenly jump up with a little backfire

- Sitting in my driveway in neutral, if I hold the revs at 2000, it sits on 2000 for 1 sec, then drops to 1800, jumps back to 2000, drops, jumps, drops, jumps, drops... so on - if I turn off the headlights, it holds steady at 2000.

This problem has been around for quite a while. In that time I have replaced: fuel pump, all fuel hose, dizzy rotor + cap, spark plugs.

Any ideas would be great, I really thought it was a fual delivery problem so I rehosed it and that has proven me wrong.

Could the alternator be causing this? Maybe if it kicks in then turns off, on, off etc.? I definitely hear it taking more load when the lights come on.

Cheers

simple test, unplug the alternator... start car. Try all the tests again, if it runs fine then its the alt.


actually i dont know if that will work with injection.. worth a try anyway

-James

Sounds so simple, why didnt i think of it :) I will give it a go, but I dont know about my battery keeping up with the headlights on! Probably will die, not enough amps im guessing?

Any other thoughts?

Cheers

Check all your grounds. Battery cables, wires to the starter, etc. Sounds like it could be a grounding issue. Good luck...

Hmm I have checked all grounds, replaced the earth battery lead...

Something I didnt mention before.

This doesn't happen when the engine is cold... but after running for maybe 20 mins and thrashing it around!

I'll take another look at grounds.. and try and check as much wiring as I can.

Cheers

bump

Just a clarification here! Probably a pretty important one.

It's only after having some electrics on for about 5 minutes.

In daylight I get home sit in neutral holding it at 2000. She holds fine.
Turn on the headlights, wipers and fan and the tacho drops a few hundred rpm but I dont thin the engine is affected. A few minutes later the tacho starts jumping up and down and the engine does the same. Turn everything off and it's steady again.

This sounds like maybe my battery or alternator?

So the battery isn't holding its charge properly or the alternator isnt charging consistently?

Thoughts/ideas/criticism/etc. Welcome!

Cheers

You have a short somewhere. Try turning things on one at a time to try to narrow it down. The short is draining the power to the point that it is affecting your engine performance. Tach jumping around is a sure sign of a short in the electrical system. My bet is still on a bad ground somewhere. Did you check the wiring to the starter?

Anyway, that's my guess. Wouldn't hurt to swing by an autoparts store and have them test the battery and alternator. Of course, a short somewhere could give a false positive on either of those systems. Good luck, and keep us posted....:)

If it happens what the car is warm - then it is likely a corroded wire somewhere. I agree with the grounds problem.

BUT - I would also check the fusible links, and make sure they are in good shape. It's also a good time to replace them.