Car is a 91 CB Station Wagon, here is the issue right at 3k RPM the car has a lil burp and seems to miss, then picks up real quick... like a hiccup...we can't figure it out. Swapped plug wires, dizzy's, new platinum ngk plugs, had p13 in it still had the issue now has p28 crome and tuned, after tunning still has the issue, we are left scratching our heads, next is fuel pump upgrade and swap fuel filter for a new one. Dizzy has all new internals.

 

Fuel filter, valve adjustment. Then this: https://honda-tech.com/zerothread?id=2016969

 

what kind of ignition wires?

 

we swapped my NGK blue wires over which are ran in my car so I know there good to his, still same issue...swapped dizzy out of my running car...still same issue.... so we put his old Euro R plug wires that came with it back on...

The guy that modified the harness is a wire nut so I am definetly thinking it's not a wire issue...

The valves seem to be fine no adnormal noise seems quiet. It doesn't have EGR, p28 ecu and crome, EGR has been blocked off and EGR ports on Euro R manifold have been plugged at the flange...

 

So fuel filter then..

 

A clogged fuel filter (or other fuel supply problem) would be worse at higher injector duty cycle levels I think.

You say it was tuned, but if it were me I'd start tweaking the fuel/ignition at the problem part of the tables. Sometimes people will only tune WOT, and driving around at part throttle will give you a big fuel trim that then throws off the WOT tuning anyway. Log it if possible. Another thing you can try, get the car warmed up or whatever to the point that you are seeing the problem. Pull over, reset the ECU, and see if it goes away for a little while. If it does, then do some street tuning of the part throttle and cruise tables.

Has anything changed since the tune was done? Does the fuel pressure regulator have a vacuum line to the manifold?

Could also be an iffy ground on the coil or engine harness letting EMI through (which is why I asked what kind of spark wires you had). I had a similar problem on a car using el cheapo solid copper wires. There is an important ground on the cylinder head near the distributor; wouldn't hurt to check that.

 

This sounds similar to the hesistation problem many people have had issues with on H22 series setups. Some people have said its a knock sensor related issue. So you could try running a P28 ecu with the proper fuel/timing maps or try replacing the knock sensor and see if that fixes it.

 

well do u have anything to monitor the knock sensor to see if maybe its seeing something and causing it to retard timing for a slight second.