Hi idle when warm after tune-up

[Mr Blotto]

Hi Y'all

Yesterday I replaced my points, reset valves and reset timing. Everything is running and sounding great, but I noticed that after driving for 45 minutes last night, my idle was a bit high (I don't have a tach hooked up, but I imagine it was around 1k RPMs). Would a vac leak cause this? I wonder if I pulled a vac line out while I was doing my work - buy why the high idle only when warm/hot?

Any ideas?

[drober23]

How were things running before the tune-up?

If you were somehow compensating at cold start to get a good idle, fixing those problems can then cause a higher idle when warmed up. One example I can think of is a bad auxilliary air regulator. If it doesn't give you enough air at idle, folks are tempted to mess with the idle mixture screw on the AFR. Then, when the engine is warm, the idle is higher.

Just a thought to get the conversation started.

[vdubyah73]

i have carbies. highway hot=high ldle for me too. could be a vac leak, or in my case i think the engine gets just big enough from heat to alter my linkage, which is adjusted for around town temp. i kinda like the high rpm, specially sitting at a long red light at the end of the exit ramp. helps with o/p and keeps the cooling going. idle speed can be spec'd as high as 925 ± 75 for 79 and later automatics.

[Mr Blotto]

It was running good before I did the points/timing/valve adjustment (but it seems smoother with more power now). The points were a bit pitted, and I had a new set around so I threw them in. I didn't get a chance to drive it today - I want to see if it will do it again when hot.

I checked for loose vac lines, and everything seemed tight. It wasn't really that high of an idle, just higher than it was before when hot.

Thanks for the replies!

[Mr Blotto]

Well, after several long drives, I think I am mistaking a smoother running engine for a higher idle.

I checked every vacuum hose I could see and everything is tight. Bus runs very smooth.

Sorry for wasting bandwidth...

[Amskeptic]

Well, after several long drives, I think I am mistaking a smoother running engine for a higher idle.

Nah noo. No. We accept numbers here. You put tach/dwell meter on engine at warm idle.
You report idle speed in rpm here:
______ rpm

Then I TELL you if your idle speed is too high, just right, or too low.
Despot Colpot

[Mr Blotto]

Well, after several long drives, I think I am mistaking a smoother running engine for a higher idle.

Nah noo. No. We accept numbers here. You put tach/dwell meter on engine at warm idle.
You report idle speed in rpm here:
______ rpm

Then I TELL you if your idle speed is too high, just right, or too low.
Despot Colpot

OK - before I threw my back out today, I managed to get the RPM readings on a HOT engine (and I mean HOT - 102* here today). The meter fluctuated between 940 and 980.

So what say you?

[vdubyah73]

perfect idle speed