50 rpm idle hunt on 78SC 3.0L

[lespaul]

I just put new intake boots on my 78 SC to correct an air leak. Set the mixture without an analyzer using techniques on this site. Might be slightly rich but runs nice and cool and even through all RPMs under a heavy pedal. Good power and acceleration with no hesitation, hiccups, grumbling or back firing. Idle set at 950-975. However, after warm up, I get a 50 rpm idle hunt.

What might cause that?

[DRACO A5OG]

As you wrote, it may be a but rich, try leaning her out a tad see if that will clear up the minor hunt???

[Reiver]

Rich mixture can do that...lean it a tad until it stops hunting but the idle does not increase in rpm.

[lespaul]

Thanks. I did try that but it started to hesitate at 4-5000 rpm with a heavy pedal, so I went back to a tad richer and the hesitation went away. It doesn't bother me since I don't sit at idle much but it is not correct. The car was not designed to hunt like that.

[Joe Bob]

Still sounds like a leak. You need an analyzer AFTER hunting down leaks. Propane or ether spray....listen for rpm changes.

[lespaul]

I will try just a tiny leaning and see what happens.

[911SauCy]

Originally Posted by lespaul

I will try just a tiny leaning and see what happens.

thats your best bet

[Flat6pac]

Years ago, I was taught to enrichen until the engine starts to seek an idle, then lean it back until you're smooth, then adjust the air on the TB for idle speed.
Bruce

[Reiver]

Originally Posted by Joe Bob

Still sounds like a leak. You need an analyzer AFTER hunting down leaks. Propane or ether spray....listen for rpm changes.

A water mister spray works fine too...drops the rpm when there is a leak and you can't blow anything up.

[c2kid]

I would think vacuum leak as well. on the wide side maybe breather leak. cheers, Geoff

[lespaul]

Leaned it a hair and now have a 25 rpm hunt. Gonna lean it one more hair. Will report back.

[lespaul]

Down to an intermittent 10 rpm hunt once in a while. Gonna lean her one more smidge. I don't think I have any significant air leaks -- plenty of room to adjust idle as needed.

[911SauCy]

10rpm hunt...on a 37 year old CIS car. You're dialed in just right.

[tkmoore]

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[lespaul]

I did not do the final lean. Instead, I put some fresh gas and a dollup of Marval Mystery Oil in and ran it up to red line a few times. No hunt at all now, rock steady at 950 rpm. I am putting a fork in it and calling it done. Thanks for all the advice.

Brad

[lespaul]

Here she is with a fresh Brazilian Wax Job.

[DRACO A5OG]

NICE!

A bit OCD, eh? Well, I think we all are :-) for our babies.

Yeap an Eyetalion Tune Up once in while is a good thing :-)

Congrats Brother,

Jim