Engine Stuttering Options

[GulfRacer]

I'm hoping some collective wisdom can help me through a frustrating problem. I have 1974 Bumblebee that I've owned for about 6 months. The 2.0 was rebuilt to a 2056 shortly before I purchased it. It has a Raby 9590 camshaft, original D-Jet and 123 distributor. When I first got the car, it was running great. It has since developed an intermittent stutter/bucking. It occurs most commonly around 3000 RPM when cruising, but once it happens, it continues when applying throttle. It doesn't usually occur until the engine has warmed up - the first several minutes of the drive are usually good.

I replaced the throttle sensor board which did not solve the problem. I disconnected the throttle sensor, and the problem is still present. I replaced the fuel injection harnesss which did not help. The fuel injectors are all new with the engine rebuild, but cylinder 3 injector stopped firing a few months ago, and I replaced it with a new one.

I'm at a loss as to where to go next. Any advice would be greatly appreciated.

Jason

[Lockwodo]

Would a faulty MPS cause the lean condition and missing?

[emerygt350]

Would a faulty MPS cause the lean condition and missing?

Normally no, a faulty mps is normally a cracked diaphragm and that leads to a rich condition.

[emerygt350]

Would a faulty MPS cause the lean condition and missing?

Normally no, a faulty mps is normally a cracked diaphragm and that leads to a rich condition.

Have you checked your plug wires? I have had situations where everything was fine with a loose wire until it found a better place than the plug terminal to jump to ground, and once it found the new route it wouldn't go back to the plug.