Idle Help

[RebelYankee]

So battery is at 12.5v resting. I propped open the butterfly and did the smoke test, but I think my resonator is shot. The clamp was stripped from over tightening and I think it's deformed because smoke was pouring out of the throttle body. I had it sealed with a piece of innertube, but didn't put it back on when i did the test. Didn't see smoke anywhere else.

 

[djkaosone]

You can get any 3" clamp to replace the broken one.

 

[RebelYankee]

Thanks. Actually it has to be thin. NAPA carries them. Called "European Clamp".

 

[RebelYankee]

So still troubleshooting. I replaced both MAF sensors and still have the low idle. I also found that if I shut down the truck and restart it, it starts with a low idle. If it's running and I come to a stop, it takes 10-15 seconds before the idle drops.

Thinking about resetting adaptations. Thoughts on if this is a bad idea?

Also thinking it may point to the battery since right after a restart it goes directly to a low idle?

 

[itsaguything]

Well, I reset the adaptations, once a year, every year.
But I’m not convinced that would have anything to do with idle.

 

[RebelYankee]

I reset the adaptations primarily because I replaced the MAF's. Will report back after a while.

 

[jlglr4]

Did you get that throttle clamp replaced to fix the vacuum leak? No change?

Just so we’re on the same page, by low idle, you mean around 620? My scv6 idles at about 680, so not all that different. Wondering if 620 is actually in the normal range. Anyone else here idling that low?

It’s normal for the cold start idle to be higher, then drop to around 680. I don’t recall my car idling high after coming to a stop (while warm) then dropping into a lower idle 10-15 seconds later. That sounds a little off to me. How high does it idle when you first come to a stop?

 

[jlglr4]

Also thinking it may point to the battery since right after a restart it goes directly to a low idle?

With respect to the battery, what I had in mind was not actually the battery, but the alternator putting a little more drag than normal on the belt which might drop the rpms a bit and make the car shudder. If the alternator is failing (or maybe the battery too), it might be running too high a duty cycle and putting extra drag on the pulley.

There’s also a known issue with one of the idler pulleys going bad. It’ll usually start making kind of a hum, and it’ll start to eat the belt. But I imagine that can put some extra drag on the belt and pull your rpms down a bit.

 

[powershift]

Mine can idle a little funny, but its not a defect or a problem. It has a tame rumpity, _rump muffled sound like it has an aggressive cam lope. Give it slight gas and it clears up. Post a vid of your idle problem.

 

[RebelYankee]

Thanks. I'll see if I can get a video.

When I come to a stop, it starts to idle about 680 or so, then after 15 seconds it drops to 620ish. When it drops, it idles a little rougher, and sometimes dips to 600 them comes right back to 620. If the car is warm and I shut it off, when I immediately restart it goes right to 620 and does the dips to 600.

I'll check the belts too and see if I notice anything.

Appreciate all the thoughts! I don't mind throwing some money at it, it's got 95k miles and some things may just need replacing. I know the battery is over 4 years old, but it does test fine. Maybe not a bad idea to replace it. Other than this idle thing, it runs great.