2500 RPM stumble partial throttle 2.0 -4 Options

[SVG223]

2400-2600 rpm stumble with partial throttle, stumble goes away under full throttle. Runs smooth at all other RPMs. Pulled the plugs, a little lean maybe?



Edit 3-17-25 I found a possible cause; worn distributor bushings causing a variation in the points gap.

[Superhawk996]

None at of those plugs are lean

[emerygt350]

None at of those plugs are lean

Maybe I don't understand your post but are you saying those plugs are not lean? They look dangerously lean. Baked on white powder with little orbs of metal isn't something I would want on my plugs.

[Superhawk996]

None at of those plugs are lean

Maybe I don't understand your post but are you saying those plugs are not lean? They look dangerously lean. Baked on white powder with little orbs of metal isn't something I would want on my plugs.

Those plugs are no where near lean. Brown / light grey would is completely normal plug color.

The little orbs and the flaking you see are called glazing

The glazing is a result of the incomplete combustion is occurring when the engine is stumbling and missing during the part throttle acceleration acceleration problem he’s having. The glazing comes from the plug heat cycling rapidly as combustion happens and then doesn’t happen. The deposits occur when the combustion isn’t complete (ie missing) and then that deposit gets baked during the time when combustion is occurring.

Solve that part throttle stumble and the glazing goes away

[emerygt350]

None at of those plugs are lean

Maybe I don't understand your post but are you saying those plugs are not lean? They look dangerously lean. Baked on white powder with little orbs of metal isn't something I would want on my plugs.

Those plugs are no where near lean. Brown / light grey would is completely normal plug color.

The little orbs and the flaking you see are called glazing

The glazing is a result of the incomplete combustion is occurring when the engine is stumbling and missing during the part throttle acceleration acceleration problem he’s having. The glazing comes from the plug heat cycling rapidly as combustion happens and then doesn’t happen. The deposits occur when the combustion isn’t complete (ie missing) and then that deposit gets baked during the time when combustion is occurring.

Solve that part throttle stumble and the glazing goes away

Interesting, i am trying to find my old post when I had plugs like that and everyone yelled "lean!!!" but I can't find it (2022?). It would have been good to know that is a sign of something else.