Take this bulletin to your transmission place, or Honda dealer and have them fix your car.
January 1994
Technical Bulletin # 207
^ Transmission: F4
^ Subject: In and out of lockup
^ Application: Honda
Honda Four Speed
In and Out of Lockup
85-87 Prelude with Fuel Injection 86-89 Accord
The above listed cars come with the F4 model transmission. One annoying habit that this unit can develop is a hunting shift into and out of lockup at cruising speed (usually on the highway).
Although this problem can be caused by torque converter problems and internal transmission control or circuit difficulties, almost every occurrence of this problem can be traced back to the t.v. cable being out of adjustment.
The F4 unit has two throttle valves, t.v. "A" and t.v. "B", controlled by the some cable. These throttle valves, aside from controlling upshift and downshift speed and feel, control the shift times into and out of lockup (Figure 1).
The F4 uses t.v. "B" to unlock the converter when the throttle is at the idle position. At the idle throttle position, t.v. "B" is at 0 psi. This allows the L/C cut valve to cut off the oil pressure that operates the L/C shift valve.
Once any throttle pressure is applied, t.v. "B" begins to rise, moving the L/C cut valve against the spring, allowing cpc pressure through the valve.
Hunting shifts into and out of lockup are usually caused by the t.v. cable being adjusted too loose in an attempt to compensate for some other problem that is causing late or harsh shifts. The reduced throttle pressure "masks" the real problem by making the upshifts feel better, but now t.v. "B" pressure drops to 0 psi at light, or cruising throttle positions instead of only at 0 throttle. This is what causes the lockup shuttle-shifting.
There is only one way to set the throttle cable position on this unit (or any other Honda unit with t.v. controlled "clutch pressure control") and be sure that it is set correctly.
Install a 0-100 psi pressure gouge into the t.v. "B" pressure tap (figure 2). You must use a 0-100 psi gauge, because a gauge with a higher rating will not be sensitive enough.
Get the engine up to operating temperature and running at curb idle, in drive. Make sure you. show 0 psi on the t.v. "B" tap, even if you have to back off the cable adjustment.
Slowly apply pressure to the gas pedal while you watch the pressure gauge. At the exact throttle position where the engine speed begins to rise, throttle pressure "B" must begin to rise above 0 psi. As you press the throttle to the floor, t.v. "B" should rise to at least 100 psi.
If throttle pressure "B" behaves any other way, the problem can not be adjusted out of the unit. The transmission must come out to service the valve body.
Jul 23, 2006 at 11:36 AM
