Hi all,
I just bought a beautiful civic cvcc hatchback ED3 (California) with hondamatic transmission and only 84000 miles. It's in superb condition with one exception : the acceleration performance in either range 1 or range 2 has a dead spot between idle and high rpms. Acceleration is strong for the first inch and a half or so of pedal travel, then engine bogs down for the next three inches of pedal travel, then returns to stronger accel for remaining pedal travel to the floor. Its like a flat spot. I tried richer & leaner idle mixtures, but hesitation remains. With choke on, acceleration is better, but the dead spot remains although narrower. I have replaced spark plus and same results. I tried adjusting main and aux float levels and same results. This seems like a solvable problem. Any ideas out there?

 

Additional info: under no load (engine running in Park/Neutral), the throttle/rpms rev up normally with a smooth, continuous ramp. No sign of a flat spot or hesitation. When I am in gear under load, the acceleration is good from a dead stop until I push the pedal beyond a point. If the car is moving slowly (low rpm's), the acceleration never reengages even down to full throttle. As I hit higher speeds/rpm's, the throttle power returns closer to the floorboard. Does that make sense?

 

Sounds like it's time to rebuild the carburetor. OEM is discontinued so, you can either get a rebuild kit like at rockauto.com or buy a new/rebuilt one but, they're kinda pricey.

 

Great parts website. Gasket kit on order. Much more to offer than other sites. Will update here when things get further along.

 

While I'm waiting for the carb gaskets to come in the mail, I think I'll check out the distributor. It has a vaccuum assisted timing advance / timing retard function that might have an engine load / rpm response that follows my problem if it's not working right. Maybe that will jog a few memories?

 

Not really but, it wouldn't hurt to check for vacuum leaks.

 

Problem Solved!

After finding and fixing a number of failing components without successfully addressing the primary symptom (power dead spot in middle of throttle), I have finally got the civic running like a sewing machine! Root cause? Carburetor obstructions and deposits. Found very fine "coffee grounds" inside the carb bowls.

In this troubleshooting exercise, I have fixed a bad distributor diaphragm and advance plate (with NOS disty), bad thermosensor, bad vacuum lines, bad ignition coil, and clogged-up carb. I feel great about all of the corrective actions that I've ended up with after this whole thing.

One more thing... lean out the auxiliary mixture screw 1/4 to 1/2 turn from factory setting to get a smoother acceleration curve.