Note: All duty cycle information, adjusting and testing procedures are now in one complete document.
Please click here to open/download the complete guide in PDF format.
Before testing, let's understand the frequency valve's function. On CIS-
The frequency valve's duty cycle is measured on a 0 to 100% scale. If the duty cycle is at 50%, this means the frequency valve is open 50% of the time, and closed 50% of the time. Conveniently, the duty cycle can be measured with a dwell meter set to the 4-
To test your frequency valve, you will need a DVOM and test light, along with a relay jumper wire. If the valve is not buzzing and/or vibrating (remember, that's what it should be doing!), follow these steps:
The proper method for setting your car's timing requires the use of a timing light. If you're without a timing light, use the Bad Habit Rabbit's static method until you can set the timing properly (you can also download the DIY Timing Guide):
"All of your VWs have marks on the rotating parts to denote 0° TDC. The cam has a dot that lines up with the valve cover. The flywheel has a notch that lines up with the center of the hole on top of the bell housing. The distributor has a slash that lines up with the rotor. Line all of these up and your car is at 0. No advance. No retard.
In a pinch, I've put the car in 5th gear (with the car off!) loosened the distributor and pulled the car forward until the advance mark on the flywheel appeared in the little timing hole. I then turned the distributor until the hash mark lined up with the rotor and tightened her down. If your flywheel notch is at 3° or 5° or whatever, now your distributor is at 3° or 5°. It's probably good for keeps or at least until you can get your hands on a timing light, but it DOES work accurately!"
It’s very possible that your air/fuel mixture adjustment hole still has its anti-
The following tampering instructions are courtesy of tolusina of VWvortex.com:
“The easiest way to [remove the anti-
The other tamper method requires drilling a centered hole in the plug, screwing in a sheet metal screw and pulling the screw up. You've got to be sure in advance that the drill bit used is small enough that the sheet metal screw you choose will have plenty to grip. Also, grind the point off the tip of the sheet metal screw so it doesn't bottom out.
Oh, yeah; you can't drill all the way through the aluminum plug [because] there's a floating steel disc in the bottom of the plug that will just spin when the drill bit hits it. The steel disc is to prevent drill chips from dropping inside. The steel disc is also what a pointed sheet metal screw will bottom out on before the rest of the screw gets a good grip.
If you booger things up with a drill and sheet metal screw, no worries; flip the assembly and punch it out, bottom-
2: Oxygen sensor (green wire)
4: To oxygen sensor wire (black wire)
5: Ground (brown/white wire)
7: Fuel enrichment switch (gray wire)
8: Power from Lambda relay (green/yellow wire)
12: Oxygen sensor thermoswitch (brown/red wire)
15: Frequency valve (brown/blue wire); up through 1987
16: Ground (brown wire)
17: Duty cycle test connector (blue/white wire)
21: Frequency valve (brown/blue wire); from 1988
26: To pin 33 (white wire)
33: To pin 26 (white wire)