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

[Ishley]

I’m wondering if you should check the spray pattern on the fuel injectors. It’s a
No cost item. I do 2 at a time on the same side. Disconnect the coil (no sparks during this operation) take out the 10mm nut and pull the injectors out. I use 2 small dishes to place the injectors in… have a helper crank the motor and watch how the injector sprays. It should be a nice fine pattern.

I had one that would dribble somewhat and that was the cause of my intermittent problem. It’s an easy fix and it’s free to check.

Just a thought.

[GulfRacer]

I’m wondering if you should check the spray pattern on the fuel injectors. It’s a
No cost item. I do 2 at a time on the same side. Disconnect the coil (no sparks during this operation) take out the 10mm nut and pull the injectors out. I use 2 small dishes to place the injectors in… have a helper crank the motor and watch how the injector sprays. It should be a nice fine pattern.

I had one that would dribble somewhat and that was the cause of my intermittent problem. It’s an easy fix and it’s free to check.

Just a thought.

I initially considered the possibility of a failed injector, but I don't believe this would explain the erratic behavior I'm seeing in the noid light.