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.

[brant]

Agree with Superhawk.

All of the basics first
Timing valves dwell? And plugs. Fuel pressure to stock. Check the cht (that is what they put the resistor on…. Not the MPs). I would not recommend a rheostat. As it changes the mixture across all rpm. Where as a MPS tune adjust for engine load and not at all rpm. I wouldn’t ever even try to mess with an MPS unless you have an AFR installed on the car

[SVG223]

Agree with Superhawk.

All of the basics first
Timing valves dwell? And plugs. Fuel pressure to stock. Check the cht (that is what they put the resistor on…. Not the MPs). I would not recommend a rheostat. As it changes the mixture across all rpm. Where as a MPS tune adjust for engine load and not at all rpm. I wouldn’t ever even try to mess with an MPS unless you have an AFR installed on the car

Thanks for the info, this all makes sense. I set the timing at 29 last year but I will soon need to reset it when I replace the distributor seal. I would love to get a CHT gauge and a AFR gauge sometime in the future. My analog clock in the center console no longer works and would like to put one in its spot.