Idle Surge Part II- The Saga Continues

[silvermachine]

Hey all, had a bit of an idle surge on my bus since I got it. Surges about 50-100 RPM, probably a little less but it’s very audible. Was going to just adjust the buffer screw and reset the idle but I just noticed the ammeter is the surging in synchronization with the engine.

That points to it possibly being an electrical issue, so now I’m thinking mechanical adjustments might not help with this issue.

Though, I probably still will perform the aforementioned repairs. Because it is possible it’s just taking more power because of something mechanical.

Anyone dealt with this before? Was it an electrical issue or mechanical?

Gonna look into it tomorrow. What components should I scrutinize first?

Thinking I might adjust the idle first and see where that gets me.

Short video attached. Hopefully you’ll be able to hear it.

Many thanks for any insights!

https://m.youtube.com/watch?v=hju3S6...ature=youtu.be

[Booyah45828]

First off, you need to put your engine in your profile or at least in the post, so other members know what you're working with. I get that your bus is an 88 gmc, but there were several engine options available in gmc buses in 1988. Help us help you.

Second off, that gauge isn't an ammeter but a voltmeter. Why it's fluctuating with the idle is anyone's guess. Stock gauges like that aren't really noted for their accuracy, so take a handheld voltmeter to the batteries and see if the fluctuation is actually there. If the voltage is actually fluctuating at idle, it could be a bad alternator or voltage regulator, or it could be an electric load kicking on and off causing the alternator and engine rpm to fluctuate.

[Native]

You also might like to tell us what speed the engine is idling at in the video.


Are your batteries fully charged?


I could see the voltage output from the alternator being a little low if the engine speed is low, so the voltage would follow the engine speed to some degree. Does the voltage keep steady at a steady engine speed faster then idle?


Of course, this does not explain the surging.