I have posted several times on this and not been able to figure out the problem. I have pretty much gotten fed up with this problem.

Here are the specs on the car:

B16B stock except for CAI
P28 ECU using Crome, set to Stock Type-R specs
Manual Transmission.

I have replaced the following, fuel pump, filter, plugs, wires, rotor and cap.
The symptom is this when at cruising speed on the highway in either 4th or 5th gear, at 4,000 rpm the car feels like it is bucking or jerking( this is with very light pressure on the gas pedal-think putting your foot on an egg gently so it does not break). I recently replaced the catalytic convertor with a test pipe and a new front 02 sensor. I am going to be replacing the exhaust within the next two months.

The guys at the local performance shop where I have had all my work done have not been able to find an explanation for this problem, despite having my car in several times...

I am completely stumped over this and would appreciate a solution to this problem...

BTW, it is only noticeable at 4k rpm, no where else in the rev range and ONLY under the conditions I described. If I am anywhere UNDER 4,000 RPM, it is not noticeable, and WOT performance is not affected. In addition, fuel mileage is not noticeably affected as I recently drove a 90 minute round trip and got 45 miles per gallon on the high way...

Any answers would be greatly appreciated...

Thanks in advance

 

Oh I forgot to mention, the needle on the tach stays steady, no jumping around and the car idles fine.

 

BUMP

 

BUMP, I KNOW you can read this post...

 

ANOTHER BUMP

 

check the tps voltage maybe?

 

No need for such frequent bumps.

You might want to test the coil, igniter unit, and the three distributor sensors.

Any CEL codes?

 

I suggest checking that the ground that attaches to the thermostat housing is tight, corrosion free and that the wiring is free from breakage. That particular ground is known for being susceptible the harmonic vibrations.

 

And what motor mounts are you running? You could have a signal wire shorting out at that RPM due to certain vibrations.

 

I am using stock B series motor mounts, no cel codes

 

my best guss would be that you egr ports are cloged and that is what is cause your stumble at freeway cruising speed you would not get a code for this (reason your valve still work open and close and honda did not have a egr flow code yet ) also note that egr dosen't exfect performance only emission

 

have you found the prob?

 

i had this exact same problem for the longest time, and then it went away. i have no clue on what caused it to change, good luck.

 

Try the vtec pressure switch and/or solenoid. I'm having the same problem and Im pretty sure that is why. I'll be replacing it today or tomorrow, I'll let u know how it goes..

 

This may sound quite weird but check your trans fluid for low levels. This happened to me whenever I was around 2000 rpms. It was dangerously low and the gears inside my diff. were slipping

 

its the tranny cuz my car did the same thing and quit after replacing with new tranny

 

A throttle position sensor can cause your exact symptoms. Starts great, idles fine and accelerates like normal when increasing your vehicle speed, but under that light load 'crusin 70mph' the voltage output tells the fuel map (in ecu) your under a slight deceleration. End point the motor is running just lean enough to keep the motor running but not near enough to maintain the actual fuel required.

Check the TPS

 

^this. i also had the same problem but my tps was not tight and therefore was jerking aggresively but i would deff. check tps