Idle issues after alternator...perhaps unrelated.

[pub911]

The idle on my 1978 SC surges between 0 and 2000 RPMs when cold at start up until I rest my foot on the peddle for about a minute - then it settled (yes, past tense, settled) to 900 rmps, right where it should be. I suspected it was the WUR, but it was a nuisance at best so I never pursued a fix.

I've just replaced the alternator after seeing a separate issue, my charging system beginning to show signs of failure: headlights dimming with low rmps, odd idiot lights like the seat-belt light coming on at weird times, a smell of burning from the alternator, then finally, a faint glow of the red generator light on the dash.

Now all of those charging issues are gone with a rebuilt alternator. The car actually feels stronger - I am wondering if I was starving for a good spark due to the charging issues.

But this 'fix' has left me with a new problem. The same surging happens when cold, but as it warms up it begins to rev up to 2000 at idle. It won't come down by feathering the clutch. It comes down over time as the engine goes from warm to running temperatures, but only gets down to about 1,300.

Where do I start?

[SchnellSchweitz]

Do a little research on the AAR. Obviously, we do not know at this point what is causing this issue, but an intermittent vacuum leak at start-up sounds like the AAR is the possible culprit.

The AAR is located on the passenger side of the motor and sometimes gets stuck. There are many threads on this site which explain how to fix this with a little spray on lithium grease.

I'd try this fix as a first step.

[SchnellSchweitz]

Since you have a recent history where you "smelled burning," I'd also be inclined to check the wires going to the AAR. The connector should provide a constant 12V with the car running.

[pub911]

Thank you. I have read up on the AAR, WUR and vacuum leaks. I will check tomorrow, but wanted to add, after driving in 80-90 degree heat, engine temp is definitely affecting the idle. Midway on the gauge, the hottest the car ever runs, lets the idle settle down to around 950, almost tolerable. But when just 'warm' about 1/3 the way up the gauge and out of the black, it's up around 1,600. Additional thoughts and a sequence to follow after AAR voltage (assuming it checks out ok) is appreciated.

[SchnellSchweitz]

You may have it just backwards. Hot temperature may not be affecting high idle... High idle (from a vacuum leak) may be affecting temperatures.

I know I had vacuum leaks for some time that sent my temps up 10%, and sometimes more, above normal. I would make a bold statement here and say that the majority of high temp/high idle issues are generally related to vacuum leaks.

Remember to spray both sides of your AAR (holes for in/out) with lithium grease. The disc inside needs it. Let us know what you find after you do this and have checked your AAR wire for cracks and correct voltage.

[giladblum]

Hi, I have the exact same issue in my 76 2.7 , I got a WUR but didn't to the swech yet, pleas let me know if you solved the problem

[pub911]

Thanks for the replies and tag-along interest. I will tinker and report back....but it may be a few days.

[giladblum]

I just switched the WUR in my car and it is working like magic,

The idle is perfect cold and warm,