Idle not steady w/ lights on!

[Pritchard]

Hi guys and gals-

I have been quite lucky and happy with my 914 for the past few months. I haven't had to repair much of anything. (knock on wood)

I have enjoyed keeping up with what everyone else has been up to.

My engine has a tendancy to drop idle speed from just under 1000 rpm to just barely running when stopped at a light or stop sign ONLY when the lights are switched on. This happens 75% of the time that I drive with the lights on. I have not modified anything electrical. And this problem has not always been there. I have doubts about my voltage regulator. Could this be the culprit?

This topic was brought up some time ago, but I never saw an answer. Any ideas would be appreciated.

Thanks in advance,

David Pritchard

'74 914 2.0 L

[philinjax]

I don't think this is an electrical problem. I suspect ignition timing.
If you have dual carbs, it may be caused by a slight differential in the tuning of throttle stops, idle mixtures or air bypass screws.
I would check dwell and timing first and then retune the carbs.
Phil

[kena]

David, my 76 2.0 d-Jet would buck and miss badly under acceleration with the lights and heater blower motor on. It was symptomatic of a bad throttle position sensor switch. Actually the voltage regulator was malfunctioning and allowing voltage to drop under 11 volts. The bucking/missing problem immediately disappeared after replacing the voltage reg. I guess the d-jet system malfunctions when the voltage drops too low. Check your voltage regulator.

[John Rogers]

The earlier post about low voltage is correct. It is symptomatic of a weak batt/alt/reg system and it happened to our daily driver 914 2.0l. I finally replaced all three components and no problems with the lights on. Goog luck.

[prattrc]

Since he has a 2.0, I assume it has the voltage gauge in the center console. Would that show the diagnosed drop in voltage? Mine ticks back and forth with the turn signal and blips when I hit the horn.

[Dave at Pelican Parts]

Don't take the center console gauge seriously. It is mostly there for "amusement", and is not a good indicator of the health of your electrical system.

That said, cleaning up all of the fuses and all of the grounds could have the effect both of lessening (or eliminating) this problem, and of making the "weird" behavior of the voltmeter less.

--DD

[John Rogers]

As Dave said, don't trust the voltmeter in the console to completely accurate. The way I tested mine was to connect a fairly accurate meter to the batt terminals and laid it on the passenger seat and drove the car with the lights on, off, used turn signals, brake lights and went into reverse to see what actually happened. When the batt/alt/reg were worn, there was a drop at the batt when there should not have been and it was magnified at the console meter. As a side note, that is how you can test to see if the backup lights are actually working, as when you shift into reverse you get a dip in the voltage. I also tried cleaning the fuses and ground connections but I do that yearly anyways. Good luck.

[3D914]

Hey guys,

Both my 76-914/2.0 and my current 74-914/2.0 had the symptom of the swinging voltage gage needle when the blinkers are on.

Is this common among the 914's, or just symptomatic of the problems described here?

Thanks,

[John Rogers]

If you look at the electrical diagram it shows where the volt meter attaches and it is most definately affected by lights such as turn signals, backup lights, fog lights. Good luck.

[Joe Bob]

The stock volt meter without numbers would have to improve dramatically to "suck"....the only gauge worse is the stock oil temp....also without numbers....what are we mind readers???

Rip it out and get a new one with numbers....also consider re-wiring it so that it reads correctly. While you are at it, $hitcan the the clock that probably doesn't work, either.

30 year old gauges are like 30 year old dogs.....probably dead....or should be.

Brutal but true....can't tell ya how many times I have heard the story...."but my gauges said....." right after someone toasted the engine....

[Pritchard]

Well, after reading your replies, here's the plan:
Replace the voltage regulator. Hope that this is the problem since it is a lot less expensive.
Have already gone through all fuses and cleaned all contact points. Checked alt. belt. I was OK. Checked the voltage at the battery terminals. It was low, around 12.3 volts. I can't remember if this was with lights on or off. I'll have to recheck. The battery is fairly new and in good order.
If this doesn't fix the problem, I guess a new alternator is in order.
Thanks for all the help. I'll let y'all know what I find out.

Pritchard

PS: I checked the voltage at the terminals yesterday and the system was charging at 12.6 volts. I installed the new VR and voltage went up to 13.7. Turned on the lights, heater, and all other electricals and the idle was much smoother and dropped in RPM's only slightly. Once again, I am a happy 914 owner. Thanks for all your input!!