carb'd A20 engine sometimes stutters when idling

[mesa]

Hey guys, I did search but nothing came up. I'm having this minor problem with my carb'd A20 engine. Sometimes when the car is idling (usually when waiting for a traffic light) the car stutters. It doesnt really feel like stuttering but more like heavy engine movement. This usually happens for about 5 seconds and then it's fine again, it sometimes seems that it goes better if i give it some extra gas. The car pulls up nicely, and I have had no problems when starting both when the engine is hot and cold, but I do like to find out what the cause is of this problem.

Many thanks :)

[gyates93]

I have the same issue, it's a rough idle when the car is in gear. In neutral or park the problem doesn't exist. I don't really worry too much about it but I've heard it could be motor mounts or just that the idle is set too low. Mine idles around 750RPM in gear but at 850 or so smooths right out.

[Dr_Snooz]

I'd be looking for spark issues. Does your tach needle bounce around when you start it up? When was your last tune up?

[mesa]

The needle does not bounce around when starting up, everything seems fine. But it cant hurt to replace the sparkplugs so ill do that then!

[gyates93]

Mine's got new plugs and air filter and still has these symptoms, put if i even put the weight of my foot on the gas, they go away. No needles bouncing or trouble starting or roughness above idle, and only when idling in gear.

[g.frost]

Could be fuel deposits on valves, combustion chamber, & carb jets. An easy fix to try is a bottle of Red Line SI-1 fuel system cleaner in the gas tank ( ...if not the Red Line, it must be a Detergent cleaner with a good dose of PEA; solvent cleaners won't cut it.)
Get the engine fully warmed up and do some Italian tune up spirited driving with the PEA to blow out the crud. See if that helps.... ( mine stumbled & ran like crap after years of cheap gas. This cleaned it up, and now I use only quality gas and a maintenance dose in every tank.)

Also, when is the last time you did the valve lash adjust?

[gyates93]

I would wager never on the valve lash adjust...

I'll try some fuel system cleaner with detergent.

[g.frost]

Do a good job carefully setting the valve lash. My owners manual recommends every 15K miles. Every 30-60K is what I do, works fine, they are never too far off and some need no adjust.
At least do it more often then never... It really makes a difference.

[chaditotx]

Check voltage to the low speed cuto out solenoid. also check that o ring. this is assuming that motor is in good tune.