# Frequency Valve? (Warning! Image files included)



## TrueNorthist (Dec 12, 2013)

I am new to basic CIS-E but using the answers found in this thread (and my Bentley manual) I am within sight of a perfectly running GX engine. I just need to clear up a couple questions if I may? First, is the item centred in the first pic below a frequency valve? (Has 2 wire connector) Or is it just an earlier form of DPR? Regardless it appears to be either not working right or out of spec, because when disconnected the car runs close to perfect. That has me suspecting the O2 sensor as I have stopped all the vacuum leaks. (There were many) And yes, the mixture plug was out and clearly messed with. I have dialed it in by ear, basically set to ~1/4 turn rich after what I think is the frequency valve starts to buzz. It wasn't buzzing at all when I got the car and I discovered somewhere in here that it should buzz most of the time so I turned the 3mm hex to 1/4 past the valve starting to buzz. It runs much better where it is now with just the cold start and mild hunt at idle. 










When the FV is connected the cold start chugs away extremely rich for about a minute, (very low rpm) then suddenly she settles in at 1100-1200rpm for another 30 seconds then drops to a low and erratic idle. ~750rpm or so, slowly increasing as it warms. It continues to run better as it warms but the idle remains a bit poor -- namely it hunts up and down fairly quickly and not severely. About 50 to 100 rpm hunt with a kind of mild misfire like it is idling too lean. Otherwise it runs strong with no hesitation nor anything else really. 

But if I disconnect the FV when cold it goes through what I believe is a normal cold start: fires right up and fast idles around 1100-1200rpm, then settles into the same low and mild hunting idle, gradually improving to ~950rpm +/- 50rpm with the very slight misfire. The fuel pumps are a bit noisy and tend to change tone a lot, but I am hoping that may be down to the FV as well? At first I thought the auxiliary air reg was acting up but it is fast idling well with the FV disconnected, so it must be opening and closing well enough. Regardless I plan to pull it and inspect/clean at some point. It is running quite well truth be told, aside from the cold start and slightly erratic idle, but I never accept "good enough". I aim for perfect where possible. Helps me to sleep at night.

My plan is to throw in a new O2 sensor and see what happens. But first I will hook a multimeter to it and see what numbers I get. But my hunch is the O2 sensor is at the root of the problems here. What say ye wizened ones?

BTW, the car is an '87 Jetta coupé with a 1.8 GX. It had been severely abused by the previous owner and just about everything had been fiddled with to the point that it would not idle at all and ran very poorly while it managed not to stall. I have replaced almost all vacuum lines and checked the intake boots etc for leaks and replaced plugs, plug wires, cap and rotor, timed to 8 degrees btdc and running on Chevron Plus 89. I think I may have extremely mild vacuum leak(s) at the injector seals but in my opinion not enough to worry about, yet. I fully intend to pull all the injectors and test, clean and install with new seals etc. Just not right now. Here is a wide view of the whole engine:










Cheers!

edit: I should clarify a bit... Cold start goes perfectly with the FV disconnected, but will start to get very rough if left off. If the FV is reconnected as the cold start backs out it runs quite well but with a slight hunting condition. I am not getting a reading from the O2 sensor but my multimeter may be at fault. It is old as the hills and I think the amp circuit is hooped. It's the main reason I have not listed many numbers here because for the moment I do not have a reliable multimeter. I do have a pressure gauge and will order a new multimeter asap, but I need to get down to the wrecker and scoop some banjo fittings.


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## TrueNorthist (Dec 12, 2013)

I borrowed a multimeter and got an old dwell/tach that I have been carting around since the '70s to work, so I set the idle as close to 900rpm as I could but it hunts a bit. I also dropped the timing back to spec at 6° BTDC. I have determined that the thermo time switch energises for 5 seconds while cranking. There's 18.3Ω across the CPR @ 16 ℃ ambient and get 11.7 volts on the harness connector while cranking. Evap canister control valve is functioning normally. 5th inj has a decent spray pattern and did not leak >5 mins and also shows 11.7v @ the harness while cranking. The air flow sensor plate moves freely and passes the mechanical tests but is probably not adjusted perfectly, but it must be close. However the coolant temp sensor shows 13.5Ω @ 16℃ ambient and open circuit at 100℃, which is incorrect according to Bentley. (should be 2500-3500Ω @ 15℃, dropping to ~200Ω at 100℃) Also pinching the the aux air reg line makes no difference hot or cold, so it must be stuck or nfg. The idle boost valve checks out ok. I will replace the coolant temp sender and see if I can clean up the AAR. What is confusing is I was getting a high idle, albeit with the freq valve disconnected. 

And I should have known the O2 has no bearing on cold start, but truth told I can't seem to find the duty cycle test connector. All I see is a round 4 pin plug with 3 wires, none of them blue/white. Is that what I should use with my dwell/tach? Pressure tests to follow once I have some adaptors made up which might take a few days. I am also leaving the injectors for last because I do not have new seals and expect the current ones to unusable once the injectors are pulled. I need to use this car while troubleshooting it. 

Any guidance would be greatly appreciated.


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## TrueNorthist (Dec 12, 2013)

Fortunately I am not exactly new to troubleshooting so it was just a matter of time before I discovered the Bentley is wrong, but the absence of even one response sure shows the true colours of the folks who rule this childish place. You might have noticed I tend not to ask questions at the vortex, but being a good mechanic I had to try all the options open to me which included asking you sorry lot of mental infants. I'm not entirely sure why nobody felt I deserved a response, but I won't lose any sleep wondering. Kids will be kids after all. I have come to realise the vortex is like a treehouse filled with 12 year old boys. If you want information, first you have to brown-nose your way into the club. No thanks.


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## Butcher (Jan 31, 2001)

Whining will get you nowhere.

What are you asking? You have a lot of words but after reading them twice, what are you asking? Is that a frequency valve? Yes it is? Running rich? How do you know? Because you think so? Any readings that back that up? How do you know you have no vacuum leaks? Smoke test?

Again, you have a lot of words, but I have no clue what you are asking. The biggest issue with CIS is that people here [and in the shop] have no clue what they are talking about. They do know how to replace parts and boy, there are many that do. They also do not have the complete tools to check the system. After making the basic fuel mixture adjustment [hot idle, frequency valve should fluctuate the same at high and low RPM's]. Usually between 30-50%. The fuel pressures need to be tested next. Don't have a tool? Then get one. To cheap to buy one? Then send the car to the shop that has one. Can't find a shop, then buy the tool. Of course, the ignition system needs to up to par. 

If you think a new [or used part] is good, then you should not be working on a car. Diagnosis is where it is at. Replacing parts because you think it is a good idea not. Lots of parts replacers here. Sometimes we are too lazy and just swap parts, we all do it but that does not make it right.

CIS is a very easy fuel injection system. The people that work on it, normally are too lazy to do it right. Coming here and expecting professional answers to a complex issue is nuts. We are just enthusiasts. Rarely does one come on with 30 years of experience. If you want that, try IATN [but if you think they are much better than here, I would not hold your breath].

BTW, lighten up a bit. If you want help we're here, but when it comes to a complex, not well written thread, it's hard to respond. Heck, we're only 12yr old kids too busy brown nosing.


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## ps2375 (Aug 13, 2003)

That is not CIS-E, it is CIS-Lambda. There is no such thing as "basic CIS-E" that I have ever heard of.


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## Butcher (Jan 31, 2001)

You're right, but he is pouting up north cause no one would help him.


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## ps2375 (Aug 13, 2003)

Now is the perfect time to switch to MS, almost cheaper than buying reman parts to the CIS and def easier to tune and fix. And lots more help available for most people.


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