bentwings

Lately I noticed my truck idle speed changes.
Cold it starts then idles about 1050. As it warms up it goes to 1100 rpm.
Then driving further it varies when I stop from 950 to 1100. Occasionally it will,drop to normal 875.

There is no surge. My fuel pressure is steady between 10 and 13 psi depending on load.

The drop of about 100 rpm when coming to a stop seems to work ok regardless of final idle speed.

It's like the throttle is sticking.

At first I thought ther might be something wrong with the tach not reading correctly but it matches indicated speed perfectly.

I have a Smarty set on 3. It's been there for at least 200k miles. I haven't checked codes yet but I haven't noticed any other odd behavior.

I have the winter start flash but it's not been cold enough to trigger this yet. It's only been a low of 24 deg f.

Is it possible that the blowby tube exhaust is getting sucked up near the air intake? I have a stock filter Assy. There is not excessive blowby. I haven't noticed any other leaks under hood.

I'll check codes later today and note them.

bentwings

Well glad to report I corrected the idle speed problem.

I checked codes first and there were none. Then using the Smarty I set the fuel program back to stock. Then reset it to # 1 timing only. Which is where it really was not 3 as I stated above. Then I went on an errand trip.

The idle now is back to normal 875. The rpm drop coming to a stop of 100 rpm is back to normal. The cold startup idle at 28 deg F is normal at 850. The idle up I can't check as it is no cold enough to trip it yet.

So apparently the computer simply lost its mind. I don't know how that happened, it just did it overnight. One day it was good next dat there were problems. It's funny there were no codes.

Mike L

Dirty rotten little electrical gremlins!! Don't rest too easy just yet as the symptoms may return. I hope that they don't. However, should they return check all off your grounds and the usual culprits that cause electrical fluttering. Occasionally I have to check and recheck my Edge J/A wiring when the motor starts running a little "funky". Usually cleaning grounds and battery terminals is all that is required.

Cheers!

Mike

bentwings

Thanks Mike, this really had me going. Thankfully everyone in the past says "grounds..." So I have those that I can find earlier this summer when I replaced the left front fender and the lower door skins. I discovered a ground I didn't know about when I took the old fender off. It got the super clean as it is inaccessible from above. It's down near the core support under the battery.

The next project is replacing the heater core. I have a new one but I'm really dragging my feet on this. It's going to take a new dash top too so I'm planning on a whole day operation.
Ggeerrrr!

Byron