• When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

First things to check on RPMs bouncing at idle?

Jimmy Van Hoose

Active Member
Local time
5:52 PM
Joined
Oct 17, 2018
Messages
35
Reaction score
10
Location
USA
74 Satellite with a 400 4 barrel. Has been idling right at 800 RPMs. Now its bouncing from 500-800. Whats the easiest things I should check and tweak first? Thanks.
 
74 Satellite with a 400 4 barrel. Has been idling right at 800 RPMs. Now its bouncing from 500-800. Whats the easiest things I should check and tweak first? Thanks.
Is the engine idle fluctuating wildly....or is it just needled bounce on your tachometer?
 
Yes, what have you touched recently. My first guess would be a vacuum leak somewhere, like maybe a small vacuum hose popped off
 
What else have you "touched?

Havent touched anything. Changed oil and filter last week. Have drove it twice since then with no problem till now. Ill start searching for vacuum leak, any chance carb needs adjusted? Thanks.
 
Havent touched anything. Changed oil and filter last week. Have drove it twice since then with no problem till now. Ill start searching for vacuum leak, any chance carb needs adjusted? Thanks.
Not likely. Carbs don't usually "un-adjust" themselves
 
After dark shut the lights off in the shop open the hood and fire it up.
Mist a little water along the plug wires. and cap area.
Also check each terminal is snapped on tight.
 
It's little things.. like this...
beerestoration2019carbrebuild 038.JPG
 
You can always try snuggung the carb down to rule that out as a vacuum leak possibility. I added a micro switch to the right front stud in my Thermoquad. While doing so I was surprised to find all four carb nuts were maybe finger tight. I had no idle quality issues but I would think sooner or later I would have due to a vacuum leak at that gasket.
 
Auto Transport Service
Back
Top